Triple Digits on a budget! Our Goal is to take a stock boat and turn it into a 100 mph power house on pump gas.
We looked long and hard to find just the right boat for this project. We came across a 1989 Sting Ray Maxxim II SVS-220 In Lyconia, New Hampshire with 580 fresh water hours on it. It's a great boat for this project. We trailered it home and dropped it in the water and tested it as is, we used our GPS to clock the boat at a top speed of 56.6 MPH with the stock 19 pitch aluminum prop and a 1/4 tank of pump gas, this is our base line test.
We will document our upgrades and performance increases as we go along, showing how you can use common sense and creative engineering to create one hot boat that is capable of turning your speedometer into the Triple Digit 100+ MPH zone all on pump Gas!
We plan to do all the best "Bang for the Buck" fixes & upgrades that really work to create a perfect balance of components to achieve the best performance and speed, without breaking the bank.
Check back soon for updates. How-to information, Pictures, and maybe even some videos will be posted here. Hopefully it will give you some ideas for your own projects.
The boat we picked up came stock with a MerCruiser 350 Magnum engine. This motor does a claimed 270 HP in it's stock form. The boat is a 22 foot V-Hull with a good reputation as well as some pretty descent reviews for it's handling and stability characteristics.
Now that we have the platform for our project, the testing begins! We will start with the basics, figuring out what common upgrades will work for us, then move on the the big changes that will make this common boat stand out with uncommon performance in our goal to take our speedo into the Triple Digit 100+ mph zone.
For equal comparison in all of our test will be conducted using standard 89 octane pump gas, with a 1/4 tank (about 10.5 gallons) using champion spark plugs gaped at .035. For the sake of accuracy we will be using a GPS unit to calculate the performance and speeds we obtain.
We ran the boat as we got it, in it's completely stock form to get a good baseline, hitting 56.6 MPH.
Installed an Aluminum 21 pitch 14 1/4 diameter Michigan 3 blade propeller. The speed increase was noticeable. We made a bunch of wide open passes and the speed was from 57.6 MPH, heading into a slight head wind, to 58.5 mph with a best of 59.1 mph. The engine still turned 4750 RPMs and we felt it could use more prop.
Removed the Stock Exhaust tips and installed Imco 4 inch straight through exhaust tips. The stock Gil Exhaust tips have an auger bit welded inside the pipe to quiet it down and to also keep water from backing up into the engine. Using the same prop from test 2 we tried it again gaining a solid 150 to 200 rpms but didn't go any faster, actually having more prop slippage do to the increased power and rpms. The boat's best speed was 58.7 mph and rpm increased to 4975 rpms. This made a little more power and rpm.
Installed a Michigan 3 Blade Aluminum 23 pitch 14 inch diameter prop everything else being the same. The boat did not like the 14 inch diameter prop. Best speed was 58.4 MPH with a max of 4800 RMPs. The prop slippage increased to 16%. It only wanted to go straight and only wanted to be trimmed in at one place. Any other place it would cavitate and be a little difficult to drive. There was a problem and we needed to solve it, as you can see in the 4 previous test we were getting nearly identical results in mph and rpm so not much was happening.
Installed a Hydro Motive Intimidator 4 blade stainless steel prop it is 14 3/4 diameter with 22 pitch. What a difference it made in handling getting on plane, even just cruise speed. To install this prop on our Alpha 1 we needed a flat zinc plate instead of the little skeg. The best run was 59.6 MPH with a max of 4250 RPMs. But now we know there is a problem and feel it's got something to do with the fuel and/or Ignition system.
We removed the water circulation pump and thermostat to install a water cross over system. This removes weight from the rear of the boat and improves water cooling as well as slight increases in HP and rpms now that you're not spinning a water pump. Using the same prop from test 5 and it's best was right at 4400 RPMs hitting a top speed of 59.9 MPH. After all the testing and reviewing notes, we're pretty confident that the real issue lies within the fuel and/or ignition systems.
Thinking I have a problem with the fuel system or ignition system, I removed the spark arrestor to see if it was a air volume issue, sometimes if the spark arrestor is not big enough they tend to choke the engine off of the necessary air flow and this will rob power from the engine and in some case it will causes the engine to run fat. If there's not enough fuel volume at wide open throttle or the carb is not jetted correctly when I remove the spark arrestor I should have a detonation problem and sure enough, running at wide open throttle showed some serious detention, the engine temps rose, and I lost about 3 MPH off the top end speed. I removed some spark plugs and confirmed that the engine was now running pretty lean. Removing the spark arrestor allowed for better air intake, but now it could not deliver enough fuel to compensate. Changing the meter rods and jets in the Q-Jet made a big difference, but it still leaned out at wide open throttle, this test didn't show any significant change at wide open throttle.
At this point I checked everything I possible could and wasn't finding the answer, so I placed a call to my good friend Joe S. He has tons of experience with these boat engine set ups and he knew exactly what it was. He said he has had this same problem him self in the past, as he explained how they use a small BB style check valve in the fuel tank pickup, and how he had problems with these before. I unscrewed the pick up from the tank to find a tiny fitting inside that had the small BB check ball as well as a ceramic filter so I removed both, I reinstalled the spark plugs and spark arrestor and headed out for another test run. The low end and mid range power increases were a huge and the boat immediately jumped on plane and pulled hard from the start as the boat quickly got up to 4500 RPMs hitting consistent runs with speeds topping 61 MPH, and a high speed of 61.6 MPH.
Thinking I was now back on track, I headed out the next day as conditions were better, I hoped to get the boat above 62 MPH. No such luck, on the first run I started getting major detention problems and the stock ignition was failing bad and getting worse. We ripped out the stock parts and installed MSD's 6T ignition box, Distributor, coil, and a set of their wires, I set the timing at 34 total, headed out again. "WOW" Problem definitely solved! This time the boat leaped off the water and pulled harder then ever before. The boat quickly raced to 4850 RPM's and topped out at 65.1 MPH. Now I'm getting somewhere!
The boat ran great for about a week but then something in the engine broke, so I took the engine apart to find a busted exhaust valve. I guess this is to be expected in a 20 year old engine with over 550 Hours on it, not to mention I've been pretty much hammering it wide open from day one. All cylinders still had good compression, so the plan were to check the cylinder that had the broken valve and if it was still good, and just overhaul or swap out the heads. We overhauled the top end putting some iron Vortech heads from a GM truck adding Comp Cams 1.6 self aligning roller tip rockers to increase valve lift, an Edlebrock Performer RPM Air Gag intake, a new Holley 650 Double Pumper, a mechanical fuel delivery system, swapped out the fuel lines with some wider diameter tubing, and used a Teague Custom Marine remote fuel filter with a water separator. I also added a mini starter to get rid of some weight, and came across a set of aluminum riser and manifolds that have separate exhaust runners cast into them like the high dollar performance manifolds, which should save about 80 pounds replacing the heavy stock parts. Everything went together well and looked pretty good, so the boat hit the water again. We did back to back testing every day for a week, consistently hitting 70 MPH at 5100 RPM's.
At $249/ea the Vortech heads and the new parts have taken the project pretty far. At this we feel the the stock 270 HP motor has been pushed pretty far, taking us from 56 to over 70 MPH, increasing compression. There is a big jump from 4900-5100 RPMS, which probably means the stock engine is out of cam. The Vortech heads actually out flow most performance head in its class size, plus increasing the spark, fuel, and air flow has brought us within 30 MPH of our goal. Now comes the hard part, figuring out what is it going to take to get that last 30 MPH out of this low dollar boat, so it can compete with, and beat the pants off, the high dollar models, and pass our mark of 100+ MPH Triple Digit speeds.
At this point I'm just out of motor, so it was time to upgrade. We put our heads together, looking and talking with engine builders across the country, explaining the goal of the project, and listening to what they had to offer. Sticking with the goal of running it on 93 octane pump gas, and after a few phone calls, one builder stuck out in our search. Steve Schmidt Competition Racing Engines in Indianapolis, IN, came up with a small block Chevy bored and stroked to 434 cubic inches that could be set up for our project. We placed our order and 5 weeks later, I hit the road to meet up with Steve and pick up my new engine. I hit the hotel in Indianapolis to get some sleep and met up with Steve that after noon to see what the new motor would do on a dyno. First pull hit 637 HP @ 6300 RPMs and 608 ft pounds of torque @ 5000 RPMs, all on pump gas. We were impressed to say the least, the HP and torque curves were fat from the bottom and all the way up. Big block power in a small block package! We could hardly wait to get home and see what it'll do in our boat!
Steve Schmidt built this 434 cubic inch small block using a Dart Little M Block along with JE pistons and Dart Pro 1 230 cc 23 degree cylinder heads with a Holley Pro Series 950 double pumper on top of a Super Victor Jr with a HVH super sucker carb spacer and a K+N Marine approved air filter/spark arrestor. The Cam shaft is a special Steve Schmidt solid roller grind from Comp Cams. We added Teague Marine remote oil & fuel filter set up and there super duty engine oil cooler, which is rated to handle engines pushing up to 1500 HP. I think this should be the power plant we need to push us to our 100 MPH goal.
It Is time to install the new engine. I had a clearance problem with our Imco Power Flow Exhaust Manifolds and the Steve Schmidt fabricated Aluminum valve covers, so I swapped them out for a set of Mr. Gasket stock type tall valve covers. The clearance problem is solved.
Our new Steve Schmidt 434 small block is installed and running and man it sounds awesome. It sounds like a healthy big block with big compression, deep and throaty.
We decided that with this much power we'd better upgrade the stock engine coupler to a Big Block Bravo unit. Lining up the engine with the new coupler was pretty tricky, it took some trying, but with a little help from our good friend Joe S, it was perfectly aligned in a half hour.
Now it was time to figure what we need to make this safe and efficient with the added power and speed increase. We called a few of our old boat racing buddies to get some ideas of what we should tackle first. The general consensus was to start with steering, so we installed a Capilano helm with a custom built Imco dual ram steering system that has a built in shower cap to keep the top of the Alpha 1 drive to keep it cool.
The stock dash board wasn't going to work for me do to the poor visibility of the gauges at such high speeds. The instrument cluster awkwardly positioned and when your pushing the 100 MPH mark, you don't want to be twisting your head around the steering wheel trying to see your gauges. We fabricated a new dash face so all gauges are clearly visible to the driver, we welded the new aluminum piece together to further stiffen and strengthen the area to easily handle the slightly heavier Capilano Helm setup. Once it was finished and tested we sent it off for powder coating.
I fired up the engine to get heat in it and check for leaks at the shop then I dropped it in the water took it for the first test drive with the new engine. I took it easy getting on plane and notice how much power I had. Im using the 22 pitch Hydramotive 4 blade for this test. I didn't want to load the motor down to hard yet, being the first time back in the water with the new power plant. Best mph was 80.1 and it was scary out of control I could not even use all the power it had and I encounter all kinds of handling issue. The back of the boat lifted real high and and the boat torqued real bad to the passenger side and it wanted to drive the left front side into the water while chime walking real bad.
I figured out the fin on the bottom of the foot was to small and not deep enough and what was happening was at speed it was pulling most of it out of the water and making it chime walk out of control. I installed a larger fin and what a difference it made speed increased to 86 mph but now we encounter blow out. We have a nose cone no reason for it to blow out @ 86 mph.
I checked the nose cone to see if I had installed properly, after checking really good it was way off. I order another nose cone from Hydra Motive and installed it properly this time. I went to go test the boat and found out I didn't have reverse so I had the gears in the lower case checked to find out the gears were shimmed wrong. The problem was 2 shims not in the correct place, so I had new gears installed and re-shimmed the lower gear case and took it back to the water, the best mph was 89 mph with no blow out but still having some weird handling issue.
I moved the battery again to the center of the boat under the rear seat and lighted up the engine hatch (not by design) a friend of mine was with me when we were out racing around and we broke the old one so I made a new one and made it lighter by a good 20 lbs. I made a jet change to the engine and took it back to the water and the best mph I achieved was 91. Its starting to handle better. The problem I'm having now is that the drive is so deep and going that fast it really jacks the boat high into the air and makes it unstable. Another problem I'm having is the water getting caught under the second cavitation plate when I'm cruising and I have to over trim it to get it to pop off the water. It's a scary feeling when you go over a little roller and the back of the boat is glued to the water and the front end goes for the sky. The higher X dimension will solve this problem and give it a better thrust angle and will glide over waves. Still not bad for a pump gas Small Block Chevy with an Alpha.
THE NEXT STEP:
I had to measure and and see were my prop center line was in relationship to the bottom of he boat and this is what I came up with. My X dimension I had 7 and 1/4 inches of distance from the bottom of the boat to the center line of the prop shaft. My Y dimension was 9 inches. My cavitation plate was only a 1/2 inch above the bottom of the boat. Some people measure there X dimension different but this is how I measured mine.
I did all the calculations taking every thing into account and I came up with a 4 inch X dimension. There were several ways I thought about raising the X dimension, I could have glassed up the transom and raised the motor and drive but then your raising the CG higher in the boat and would be more prone to chime walk thus making the boat more top heavy. I could have found a Alpha SS but they demand to much money and there only 2 1/2 inches shorter and there factory nose cone isn't the most efficient and they utilize a outboard foot. Nothing wrong with the outboard foot just to get a after market foot is thousands of dollars when for a few hundred you can make the stock Alpha foot just as hydro dynamic. So I look at the stock Alpha drive and decide to shorten it up 3 1/4 inches. This is what the cut drive looked like after it was cut up on the band saw.
Here is the drive done and welded. Its 3 1/4 inches shorter then a stock Alpha and its 3/4 of inch shorter then a Alpha SS.
Here is the drive on the back of the boat for the first test fitting
I had a clearance problem with the low water pick up tube hitting the gimble ring on the foot so I have to change it back to the Hydra Motive lower foot. Im ready to get the upper gears installed in the shorten housing and soon I will be testing it in the water.
After a whole year of R+D, here is the new shorten drive bolted on and ready to be tested. I call it the Alpha R One HD.
With the new shortened drive bolted up, its time for the water. I've waited a whole year for this moment. This is just a test session to see if the drive even works. I'm using a Hydra Motive 4 blade prop for the first test. This test is just going to be a short test to see if it gets up on plane and the drive holds together. With the drive 3 1/4 inches shorter I had concerns that it was not going to get up on plane. When I idle away from the dock I knew it was different, the boat was moving threw the water faster then usual, I hit the gas and it got rite up on plane with no cavitation. I drove it around at various engine rpms for a hour then let it cool off for half hour all was good so now it was time to hammer down on the throttle. What a difference in handling and speed, I noticed even more transom lift, but the prop had some slip to it and would not hold the bow of the boat properly. The biggest coolest thing was when you were going wide open and let off the throttle the boat would glide for a long time, it never did that before. You could take a wide open pass and just pull back on the throttle and it would keep on going. But what a ride, we drove around for 3 hours with no problems. The boats handling increased. Its a huge difference, its not even the same boat any more. The acceleration was insane way more then I ever had. It was a home run THE DRIVE WORKED and it increased performance. Took the drive apart and checked everything and it was mint, no signs of any wear or trouble and the drive oil was perfect.
Now that I know the drive works, Im ready for a top end speed pass. Going over my notes I see there is still a good amount of prop slip and I was wondering what could be done to lower it. So I look around at all the really fast boats with out drives and I noticed something they all had on there lower gear cases that I did not. A light went on over my head. So went into my shop and I made up the new piece and welded it on my lower foot. I took the boat out and noticed a difference rite away. The boat was hard to control and keep trimmed properly and it was a really harsh ride. It did a 180 from last time out in handling. In the heat of the moment I could not figure what was going on. I go to make the top end pass and under hard acceleration the transom raised higher then it ever did and I had to use more up trim then ever before, I looked behind me and i was shooting a pretty decent rooster tail. What was different this time was even with all that transom lift and over trimming the boat to get the bow up, the prop held the boat up and accelerated. I was on the best top end pass ever then the drive broke. I broke the pinion gear in the foot. This was the first major breakage of the drive to date.
Here's what happened
The new piece I added to the gear case made it more hydra dynamic, it lowered the slip percentage by 4 points it went from 10% to 6%. The prop got a really good bite of clean water. What happen was with all the torque under acceleration it raised the back of the transom really high pushed the bow down into the water. The Hydramotive prop I was using is a transom lifting prop that has allot of rake in it. So to get the bow off the water I had to over trim it. All this put such a added pressure to the drive the pinion gear let go. You have to imagine the drive trying to lift the bow of the boat lifting the transom straight up and trying to push the boat forward and to get the bow up you have to over trim the drive so now its dragging threw the water. This was probably twice the load the drive has ever seen.
I need a new prop design. The HydraMotive took me as far as it could go and it was a great prop. Now I need a prop with more bow lifting in it and less rake. A prop that will push the boat more forward and not raise the transom so much. I called a few prop people and they did not want to be bothered with me for some reason. I think the big problem is they role there eyes on the other side of the phone when I say, I have a Alpha 1 with 640 Hp and 610 Torque. behind it. A good friend of mind George F. told me about a prop place in Tennessee, called Performance Propeller Inc. I gave Tim a call and explained to him my situation and what the boat was doing and what I needed. He was very enthusiastic and said he could make me up a prop that would really work with my combination. He took his time and listen to what I had to say and we talked back and forth. This is the type of prop guy you need, some one who will work with you and talk with you. He came up with a 3 blade design one of his performer 3 prop and he explained to me for all out top end performance this is the way to go. I order the prop and 2 weeks later it arrived and man it looks good. Its a 15 inch 24 pitch 3 blade full ear.
I tried the new 3 blade prop from Performance Propeller and it was not what the set up needed. I went a lot slower and it was almost impossible to get up on plane. The best I could get it was 82 mph and if I tried to push it any faster I would cavitate the prop really bad. It had no bow lift or transom lift to it. I tested a few other props and now I know for sure it needs a full hub prop with 4 blades. I know the correct 3 blade would be a little faster but I did not like the way the 3 blade's ran threw the water. I could feel the slight vibration or a choppyness to them, the 4 blades ran silky smooth with no vibration. A four blade is easier on the drive and doesn't beat it up as bad as a 3 blade or even a 2 blade would. So a full hub 4 blade is what I need now I just need to work out the blade design. Performance Propeller is sending me a full hub 4 blade Turbo prop to try next. The thing worth mentioning is that the Hydra motive prop is not far off of what I need and If Hyrda motive could make me a new one with the changes I need, the boat will fly. Some people may be confused as to what's going on as far as speed is concerned, I can go really fast but Im trying to get the boat to handle correctly at those speeds and be safe. We took some video when testing the 3 blade. I could not go over 82 mph and could not go over 5900 rpms with out cavatating the prop really bad. At 82 mph I could crack the throttle wide open and the engine just screamed to 6500 rpms and it did nothing but slow down a little. So 5900 to 6000 and 82 mph is all it had that day we did not show how bad it was to get on plane because it was just so hard there wad no way to video that. We had to almost sit on the bow to get it up on plane.
I tried the new Turbo prop that Performance Propeller sent me and what a difference. It was a 15 x 25 pitch 4 blade full hub. The prop straighten out almost all the problems of the boat, but there still was some issue with the prop not holding the boat. I called Billy back at Performance Propeller and we talked more about what was going on and what I needed and we came up with the conclusion that I needed the Quad 4 X prop from Hydra Motive. I sent the turbo prop back and had Billy order me a 15 26 pitch Quad 4 X Hydra Motive.
I installed the prop and to my amazement it held the boat, I could hold the bow at what seemed to be 45 degree angle and just hold it there. My first pass out the boat went 96 mph @ 6400 Rpms and drove like a dream, I have my handling back. I'm still having some minor issue with torque steer and chime walking, my set up is close now and handling better then it ever did. I feel I have a drive height versus set back issue that I need to tweak and also I need a torque tab. The torque tab I feel this could be worth 1 to 2 mph maybe more. The boat was a little to high out of the water at max speed so I feel I need to shorten up the drive again another half inch to a inch shorter. I realized that the salon style seats are un safe and I feel there is a good possibility with proper seats I can drive the boat better and maybe see a little faster speed.
Now that I have the handling back, I'm looking for the hundred mph mark. I talked with several people to get some ideas and one well know engineer told me to take off the windshield and I would pick up nothing less then 3 mph at that speed I was running. He did all kinds of math formulas, had me measure the windshield. I took it off and the boat went slower. Now it's not to say he was wrong but with the set up I had when I tested it, was not good for removing the windshield. I would have had to make other changes to see the gain. I talked with a few people in racing and they told me some boats pick up and some don't by removing the windshield you just have to try it. If I had more time to test the boat I feel I could have made a few changes to the combo and I would have probably seen 2 to 3 mph on the top end. The way it was told to me was just to remove windshield and you will magical pick up 3 mph. Didn't happen. Here some spy photos of what it looked like with the windshield off. Im going to change a few things then im off to Long Island to test it with some friends that have some really fast out board boats.
I need to figure out how to take some of the chime walk out of the boat and the torque steer. I added a torque tab to the lower skeg on the drive and I lowered my seats by 2 inches. by lowering my seats it lowers the CG in the boat witch helped the chime walk. I also took some power out of the engine. My peak power on the dyno was at 33 degrees of timing. I turned it back to 31 degrees of total timing. Went to Iong Island with some friends and the adjustments worked, I went the best of 98.7 mph (Natural Aspirated). I improved 2.7 mph. The boat handle the best ever in 3 years and was super easy to drive. I don't feel the boat had any more in it. For this combination to go any faster a major change would be needed . As crazy as it sounds I'm starting to think I built the wrong engine combo. I actually have to much torque and the power range is incorrect for such a small boat and the big speed I'm looking to run. Look around on the Internet boat chat rooms and there are plenty of over powered 18 to 24 foot V bottoms and they all go basically the same speed with in 10 mph of each other. There in the 80 to 90 mph range. Some of these guys have huge HP and Torque and in reality they should be running more like 110 mph. This is why it didn't matter if I had 4 people in the boat and full tank of gas or no people in the boat, it went all the same speed. Same thing with the props, I could run a 22 pitch or a 30 pitch and it still went the same speed just different rpm. I will test this by installing another engine that has less torque.
I removed the 406 cubic inch small block Chevy engine from our 1980 22 foot team shadow. This engine produced 525 hp and 510 foot pounds of torque with a set of Steve Schmidt Gm Ported heads and Super Victor Jr intake with a 850 holley double pumper. I took the engine back to the dyno to establish a base line. After several pulls and playing with different carbs I achieved 503 hp and 498 foot pounds of torque all done by 6400 rpms. I was not looking for more HP or torque I wanted a square number 500 and 500 for the next test. This motor here makes 140hp less and 111 foot pounds of torque less then the 434 did. This is a good amount less in HP and torque. Im going back to basic and starting over. I'm back with a stock length drive with a nose cone to see what happens. I installed the engine and took it out for speed run to my surprise it went a best of 76 mph like it was on rails with a 22 pitch Hydra motive prop. The boat handle incredible but short on speed. The engine felt like it was laboring and struggling to get into it's power range. I figured that's all I was going to get out of the boat because the lack of power and cubic inch, but something has been bugging me from day one with the set up. I went back to my drag racing roots and ask my self what would I do if this was a drag car. The Answer: (Change The Gears). Im going to figure out what ratio I need and try it. I was tired of the so called experts telling me you have to run this gear ratio only and that's it. I want to see for my self.
I figured out what ratio I wanted to use but Mercury does not make that ratio so for now I had to stick with what they offered. I installed the new gear set and tried it with the 14 3/4 22 pitch Hydramotive 4 blade prop. All it did was rev the motor really high and cavatate the prop and the boat went slower. I came back to the dock and installed a 15 1/4 26 pitch Hydramotive 4 blade and to my surprise the first pass the boat went 79.9 mph. I made a few adjustments to the engine timing and the best I saw was 81.6 mph. This was a existing day because I just went 1.6 mph faster with 140 less hp and 111 foot pounds of torque and the boat handle incredible. I found a place online to make me my new custom gear set. I installed my custom ratio and broke them in properly. The best was 83.4 mph. Now Im going 83 mph consistent with no handle issue with a STOCK LENGTH ALPHA. The new ratio realy woke the motor up and now I have acceleration every were. There is no lag from the bottom to the top end, before you had that little lag then it got faster and faster then it really started to pull. Now it's snap the throttle and your there. The motor pulls hard from 2800 to 6400 rpms. So now I'm going 3.4 mph faster with a smaller motor that's half the money. My theory is when I test with the new shorten drive I should be rite around 96 mph range. I'm doubting it will go much faster because of the lack of hp and rpms. If I hit 96 mph I will be super pleased. Now that I totally understand 110% what's going on and how things work the 100 mph mark is safely rite around the corner all day long on pump gas. Now I know It's going to take a certain engine combo to achieve this goal. The 434 wasn't to far off of what is needed and the 406 is not enough. The 434 had to much torque and not enough RPM for the boat and Alpha combo. From what I have learned the smaller boats 24 or less feet you can't run huge torque numbers you almost have to set them up like a out board boat, special if your running small blocks in them. You need to run high x demenisions and a decent amount of engine rpms, some were between 6500 to 6800. TORQUE KILLS the handling and speed because it throws the boat around and plays havoc with your prop and with chime walk. Next test a 4 inch shorten drive.
I shorten the new drive to 4 1/4 shorter with a Bobs low water pick up nose cone and I added a little deeper skeg. I also intalled my new fat shaft conversion kit for the lower foot. I bolted up a 28 pitch 4 blade Hydramotive Quad 4 X wich has a 15 inch diameter. I bolted the drive up and and went out and tested it. The best it went was 94.8 mph and realy consistant 93.8 mph. The boat handle incredible smooth and fast, it poped rite up on plane and after it was on plane it went straight and fast and never realy had to use any trim and it never did any poping off the water or you never had to over trim it to break it off the water. It did not do anything crazy or scary or chime walk. Final after 4 1/2 years of R+D anybody could drive the boat. The boat drove around like it was on a pocket of air. The boat floated over all the big nasty stuff. Now I need to work on the engine combo. The engine needs a little more rpms on the top end and the prop needs a little work. The boat picked up 11.4 mph from the stock length drive test. The boat had a little more in it but I did not have a torque tab. I probly would have seen 1.5 mph gain if I had the torque tab.
It's been a long time since my last test. I removed the 406 and tested the 434 with the cam and intake change and it was better but not what we were looking for. It was still violent to drive and it still torqued the boat all over the place. I bolted the 406 back in the boat and the 406 resulted in better handling and basically the same speed. Next test I'm going to change the cam and carb on the 406. I'm looking for more engine rpms up hire in the power band.
Installed a bigger cam shaft with more lift and a little more duration. I also installed a 950 pro series Holly carb. Great results, I moved the power band up. Peak torque before was at 4900 rpms and peak HP was 6300. Now peak torque is at 5800 and peak power is at 7000. What a difference, I killed a lot of torque down low and the motor pulls hard to 6800. Result: 98.9 mph. We are using a 26 pitch quad 4 x hydramotive 4 blade prop. Boat is a little lazy getting up on plane and once you hit 5000 rpms it really starts to pull nice and I don't have that torque moving the boat all over the place. The boat handles really good and now after explaining the little problems I'm having with Thom from Hydramotive I think a little prop mod to hold the boat better and I will see my 100 mph. I gained 4.1 mph. I'm getting more engine rpms with out the boat chine walking really bad or getting hairy out of control. Now the motor pulls really nice to 94 mph effortless then have to drive it and trim a little bit to get that last 4 mph out of it. It's safe to drive now and it's still running pump gas. I'm waiting for a little cooler weather and the prop mod and hopefully I will see the century mark safely.
The boat went the best of 101 mph with the pump gas 434 small block chevy with the use of nitrous oxide 3 years ago. It was scary out of control and super dangerous and you were taking your life into your own hands. After that day it was my goal to go 100 mph safely with out the use of nitrous oxide and with it out being super scary and out of control. The best I could get it to go with the 434 on pump gas and NO nitrous was 98.7 mph. Even at 98.7 mph, I still had handleing issue and only a hand full of people could drive it. Now I'm at 94.8 mph with a motor that's 28 cubic inches and 140 hp less then the 434. The toqure is 111 foot pounds less. Anybody can drive the boat now. It's super smooth and super easy to drive. You blip the throttle and your at 89 mph like that, you dont even realize it now becaue it's so smooth. Next step is the engine combo I'm going back the 434 and making a cam change and intake change. I want to take some torque out of the engine gain some Hp and engine RPMS.
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