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MAXIUM PERFORMANCE


sgt1970-442

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310 carb indmar motor in a 99 sunsetter lxi sv-23 diamond hull. well the mods to the motor are complete and i think thats all i get out of it. the stock cast iron vortec heads were replaced with edelbrock aluminums 170cc intake runner and 1.94 intake valve and 1.50 exhaust valve. they helped buy not what i wanted. so they came off in favor of the patriot aluminum heads 200cc runner and 2.02 intake and 1.60 exhaust valves. harland sharp full roller rockers were added next this made a noticeable difference. i had to play with the jets in the carb and finally got some good seat of the pants feel out of it. as some of you know i added a set of etx manifolds in place of the cast irons, made a little difference. i'm looking at make a thin wall aluminum exhaust with an x-pipe in pace of the fiberglass mufflers. it was still lacking the punch i want so, i called comp cams and spoke with there tech dept. i told them what i had and what i was doing, hence a roller cam and lifters. more lift and duration. now theres a big difference and also had to play with the jets again. i've installed a msd rev limiter and put a 5200rpm chip in it. we've bounce it off the chip and held it to 5100rpm with a gps and a cvp stainless 13x13 prop and got 53.6 mph. same test with a 515 acme and got 52.3 mph. all of this started as a weight savings plan, shed 141lbs. the motor is coming out this winter and i'm going put it on the dyno to see where the peak hp and torque numbers are. this should be interesting to see the peak hp as i think the 310 base line is off. i think some carb tuning while on the dyno will get a few more horse. we know this motor will spin 7500rpm with no problem, but i i'm worried about trans. i've tried get some answers from indmar, malibu, hurth, and my dealer as to how many rpm's the trans can take. i know i'm not redlining it at 5200 thats why its got the chip. just wondering what some of you guys are running your direct drives are at for peak rpm. thanks steve

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Sounds like a nice upgrade and ironically as a slalomer, I was after weight reduction along with a performance upgrade. I have done essentially the same thing but with some difference in parts. Fast Burn 385 cylinder heads, they have the larger valves also, ZZ4 camshaft, Edelbrock performer RPM intake manifold and a set of Stainless Marine exhaust manifolds. Added cold air tubes to feed the intake, a custom made spark arrestor (the old one cost 200 rpm off the top) and a home made 4" exhaust system. Spent some time with spark timing and carb cals to dial it in. Total weight savings with a few other mods is at 250 lbs. Mine will pull 5500 rpm on a cool day, and runs about 54-55 mph with the CVP stainless prop, which I have tweaked on to improve it. Did a similar Acme 515 comparison, it was very close at the top end. Midrange power is much better.

I made a pretty simple and low cost exhaust system, 4" PVC pipe. Incorporated an H pipe and made my own exhaust baffles along the length of the pipes. Added the stainless 4" tips to get a 4" diameter hole the entire length of the exhaust system, that was the key. The system is several years old and works like a champ.

What was the specific effect of the roller rockers? Are they the same ratio as the original ones or 1.6 ones? Any fuel consumption effects? Did you need to change the valve covers for clearance? Did you stay with the original cam? Also, what carb do you have?

One thing to remember, these boats push the nose down as they pick up speed, so it takes a lot of hp to make much of a difference. That is caused by the hook at the transom.

Have fun on the dyno!

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woodski, to answer your questions:

the roller rockers seemed to let the motor rpm faster with no valve float issues. they are harland sharp 1.6

hasn't seem to be any fuel consumption issues, the motor is running more efficient now. valve covers are stock, but i did double up on the gaskets. mr gasket has them 1/4 inch thick. the cam and lifters have been changed with a custom grind comp cams roller cam and roller lifters. same holley carb the boat came with just been modified to meet the upgrades.

i wanted to keep the stock appearance so i had to go with vortec stuff. the intake that came on the motor is a hi rise aluminum that says malibu. i did some research and found its cast by edelbrock and is like the performer in the vortec bolt pattern.

woodski, i'd like to see some pics of your cold air intake and spark arrester, exhaust and baffles and tips. thanks steve

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Silly thought maybe ................. would adding lots of weight to the rear of the boat perhaps counteract some of the nose down attitude at high speed, actually making it faster ?

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Silly thought maybe ................. would adding lots of weight to the rear of the boat perhaps counteract some of the nose down attitude at high speed, actually making it faster ?

not if you want to keep the wake the same for skiing

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No, I don't think adding weight to the back would accomplish that. Added weight would mean more displacement, therefore more wetted surface to overcome. The key element to the drag is the transom hook, you would need to take that out to accomplish more speed. The original Corvette boast actually had an adjustable tab to accomplish that very thing. That boat did gain top speed with that, it topped out at nearly 60 mph or at least in the mid to high 50's, or someone can chime in and indicate a better number. I would not take out the hook as that is a key element to the great wake performance of the Malibu SV23 hull.

The ZZ4 cam I installed did a similar thing, really made the engine spool up quick. You really have to be on the ball if you are doing a deep water barefoot start as you can be still sitting at 40+ mph if you are not careful! What cam grind did you end up choosing? The ZZ4 cam is .474 / .510 lift and 208 / 221 duration. I have a set of 1.6 roller rockers, just have not put them on yet.

When I was talking with the Indmar folks, that manifold is made by Cutler, which could actually be subcontracted out to Edelbrock. I did a performance comparison between the original GM cast iron manifold and the Performer RPM and the were the same. The Performer was off just a small amount at the top end compared to the Performer RPM. You might want to measure the carb surface flange height to make sure which unit yours compares to.

I will look around to see if I have some pics. Mine does not look that much different, you can barely tell the stainless marine manifolds as they are black. The spark arrestor is just some door screen and a stiff screen wrapped together and made .75" taller to allow for freer air flow. I took out the original spark arrestor material and used the top and bottom sections. I did test one Zenith unit off a big block and it flowed well, the original unit I had was poor. I made an aluminum tray around the carb, looks like a smaller version of a carb based air cleaner bottom, with an open back. I then took 2 of the drink cup holders out of the engine cover and cut the bottoms off and attached some stiff hose to them and routed up to the air cleaner base. The top has a rubber seal to seal to the engine cover when it comes down. You can hear the intake hiss from the cup holders and more importantly, there is no performance loss when the underhood air gets pretty warm. The exhaust is just 4" PVC pipe, I took the 4" hose from the exhaust manifolds and just matched that up at the local Lowe's or Home Depot to get what I needed. I think the 30 degree angles are the correct ones for the transition from the hose to the flat exhaust.

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Silly thought maybe ................. would adding lots of weight to the rear of the boat perhaps counteract some of the nose down attitude at high speed, actually making it faster ?

not if you want to keep the wake the same for skiing

Anyone doing mods to increase top speed isn't a skier anyway. Or at least not a slalom skier and if they're ski racer they'd be wanting a boat doing 100+mph so definitely not a bu

Edited by uk_exile
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Silly thought maybe ................. would adding lots of weight to the rear of the boat perhaps counteract some of the nose down attitude at high speed, actually making it faster ?

not if you want to keep the wake the same for skiing

Anyone doing mods to increase top speed isn't a skier anyway. Or at least not a slalom skier and if they're ski racer they'd be wanting a boat doing 100+mph so definitely not a bu

what makes you think we are skiing at full throttle??????????

if you really read the thread you would see why the mods were done in the first place.

usable torque and horsepower at a lower rpm was a bonus, top speed is rarely ever reached on the lakes i'm on.

when you consider that peak horsepower on my motor is 310 at 4800rpm and peak torque is 375ft lbs at 3700rpm, thats been changed quite a bit as now the torque curve starts much lower in the rpm's and is broader that stock it's also nice to have extra horsepower for whatever reason. i will post dyno numbers this winter and show you the difference. i just wish i would have dynoed the stock motor. i got the stock torque numbers from indmar.

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Are you wanting higher top speed, or more power midrange. I can understand shedding some weight. Theose heads should really wake that engine up. Do you know your compression ratio is now? You may need to raise compression to fully get the benafits of the heads and cam you have.

Charlie

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Just to set the record straight, and as mentioned above, I invested in increasing the top speed of my boat and am a very serious water skier. Spend 85% of the boat time in a slalom course. I certainly think there is interest in increasing the performance level of this type of boat, particularly the earlier versions. Advantages include weight reduction, increased torque which lead to improved hole shot, improved speed control, ability to attain correct entry gate speed on a short slalom course, ability to quickly pull up a barefooter, multiple barefooters or heavy ones. If you poke around on other sites, you can see examples of people that have done similar things. In addition, some people simply find it fun to do. That is why there is an entire industry for hot rod parts.

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I seem to remember that Mastercraft experimented with a Roots style blower on one of their motors a few years ago to be used for skiflying. I don't know if that's the type of hp increase you were looking for but it should increase your top speed.

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Just to set the record straight, and as mentioned above, I invested in increasing the top speed of my boat and am a very serious water skier. Spend 85% of the boat time in a slalom course. I certainly think there is interest in increasing the performance level of this type of boat, particularly the earlier versions. Advantages include weight reduction, increased torque which lead to improved hole shot, improved speed control, ability to attain correct entry gate speed on a short slalom course, ability to quickly pull up a barefooter, multiple barefooters or heavy ones. If you poke around on other sites, you can see examples of people that have done similar things. In addition, some people simply find it fun to do. That is why there is an entire industry for hot rod parts.

That makes sense. The first post was difficult to read with no capital letters and seemed to be focused on top speed with only a small mention of starting as a weight savings plan.

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Just to set the record straight, and as mentioned above, I invested in increasing the top speed of my boat and am a very serious water skier. Spend 85% of the boat time in a slalom course. I certainly think there is interest in increasing the performance level of this type of boat, particularly the earlier versions. Advantages include weight reduction, increased torque which lead to improved hole shot, improved speed control, ability to attain correct entry gate speed on a short slalom course, ability to quickly pull up a barefooter, multiple barefooters or heavy ones. If you poke around on other sites, you can see examples of people that have done similar things. In addition, some people simply find it fun to do. That is why there is an entire industry for hot rod parts.

That makes sense. The first post was difficult to read with no capital letters and seemed to be focused on top speed with only a small mention of starting as a weight savings plan.

sorry about the small letters but i got told i was yelling with a caps so now i type like this. i never took a typing class so i'm a pick and punch type of guy.

guess i should have started this as a weight savings but i did mention it.

as woodski, we only slalom ski, the performance gains for hole shot are much better and it was before the changes 36mph was 3600rpm.

now its 36mph at 3100rpm. i think i mentioned the torque curve starts at a lower rpm and pulls a broader range up to about 3800rpm after 3800 rpm your only gaining speed. to answer you charlie yes the heads made a big difference

johnsvt: sorry should have been maximum but maxium got you to read it.

why didn't i go with a stroker kit: simple i didn't want to pull the bottom end apart. i know i could get a lot more out of this motor but feel that the 1350.00 i spent was well worth the gain. besides all that this motor has a top rpm of 4800 according to indmar. i've been running up to 5000 with and every now and then its hits the rev chip at 5200,

my original post was geared at helping others with the older carbed motors do cheap up grades that get results you can feel in the drivers seat.

i can see where some of you would think this was all about speed and i can tell ya if you check out wake side rides and look at my profile, the black 70-442 olds i have gives me all the speed i need.

i like the blower idea, i think a super charger would be a better fit under the motor cover though

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As noted, the stroker kit would be great, but the engine must come out for that. The heads and the rest can be easily done in the boat w/o pulling the engine. Bottom ends on the small blocks are pretty bullet proof, so not a great need to dump money there if one does not want to pull the engine.

Not noted, but the power upgrade with a change in prop to drop 36 mph engine speed from 3600 to 3100 rpm will show a benefit in fuel mileage. The reason, it takes the same amount of power to push the boat, but lower engine speed means lower frictional losses, thus less fuel used.

The other item mentioned back a ways, the wake is significantly improved with the reduction of 250 lbs.

Back in the mid 90's Sanger made a boat with a supercharged small block, topped out at 70 mph and had a Volvo Penta twin prop setup.

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woodski,

i'm glad were on the same page with this.. . did you ever come up with any pics of your exhaust and cold air intake set-up? i would have liked to go with the stainless marine manifolds but the price was out of the budget. i got the etx's for 700.00 shipped to me they had 40 hours on them and the guy went to a closed cooling system.

as i've said this is an inexpensive way to really wake a carbed motor up... the new boats with efi are normally 325-340hp and i just wanted to shed the weight and wake it up some.

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  • 3 weeks later...

WELL LOOKS LIKE THE MOTOR WON'T BE COMING OUT AS PLANNED, I GOT CALLED BACK TO ACTIVE DUTY. 43 YEARS OLD AND GETTING CALLED BACK JUST BEFORE CHRISTMAS. I LEAVE DEC 15TH FOR A YEAR IN IRAQ. JUST WHEN I WAS AT AN AGE IN LIFE WHEN THINGS WERE REALLY GOING WELL, THE GOVERNMENT HAS TO GO AND TURN IT UPSIDE DOWN.

ONLY THING I CAN SAY IS I'M PROUD TO SERVE MY COUNTRY,, AGAIN!

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WELL LOOKS LIKE THE MOTOR WON'T BE COMING OUT AS PLANNED, I GOT CALLED BACK TO ACTIVE DUTY. 43 YEARS OLD AND GETTING CALLED BACK JUST BEFORE CHRISTMAS. I LEAVE DEC 15TH FOR A YEAR IN IRAQ. JUST WHEN I WAS AT AN AGE IN LIFE WHEN THINGS WERE REALLY GOING WELL, THE GOVERNMENT HAS TO GO AND TURN IT UPSIDE DOWN.

ONLY THING I CAN SAY IS I'M PROUD TO SERVE MY COUNTRY,, AGAIN!

:salute:USA.gif

Thank you for your service.

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WELL LOOKS LIKE THE MOTOR WON'T BE COMING OUT AS PLANNED, I GOT CALLED BACK TO ACTIVE DUTY. 43 YEARS OLD AND GETTING CALLED BACK JUST BEFORE CHRISTMAS. I LEAVE DEC 15TH FOR A YEAR IN IRAQ. JUST WHEN I WAS AT AN AGE IN LIFE WHEN THINGS WERE REALLY GOING WELL, THE GOVERNMENT HAS TO GO AND TURN IT UPSIDE DOWN.

ONLY THING I CAN SAY IS I'M PROUD TO SERVE MY COUNTRY,, AGAIN!

:salute:USA.gif

Thank you for your service.

JOHN THANK YOU,, ITS AN HONOR AND A DUTY THAT FEW WILL EVER UNDERSTAND.

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Thank you so much for your service to this great country. Take care, stay safe. I will think of all the service people on Christmas and the holidays, you will be out protecting all of us, away from your loved ones, while the rest of us get to enjoy the holidays. Again, thanks for all you do.

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Thank you so much for your service to this great country. Take care, stay safe. I will think of all the service people on Christmas and the holidays, you will be out protecting all of us, away from your loved ones, while the rest of us get to enjoy the holidays. Again, thanks for all you do.

THANK YOU FOR YOUR SUPPORT.

STILL WOULD LIKE TO SEE PICS OF THAT EXHAUST. STEVE

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Be safe, and thanks for protecting our freedom. Hopefully when you get back you will have more time to tinker with the engine more.

I want to do many of the same mods, new heads, cam, lower end, I have EFI though and dont know how to reflash the ECU for it.

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