30' Superboat w t400's needs prop advice
02-05-2007, 11:40 AM
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30' Superboat w t400's needs prop advice
Hello everyone, and especially you Long Island Sound Superboat owners/enthusiasts.
I have a 1982 Superboat that is rigged with 400 cube small blocks and Bravo 1.5's. The boat is a pleasure to drive and handles really big waves at amazing speed and flies very well balanced. I had a 35 cigarette and in some conditons it seems faster, getting "light" much more easily. That aside, I am trying to tune the boat for the best top speed I can. I have rev limiters set in the six area, open exaust, and well built engines. They dynoed in the 420 ftlb area last year and this year I am putting in roller cams for a few more HP. I have run three types of props over the years, 23p three blade cleavers, 23p four blade hydromotives (borrowed off the cigarette) and now I use 23p mirage pluses. I think I should be in the 70's with almost 900 HP out back but am stuck in the high 60's. I use what feels like a healthy amount of trim, (almost 50% on the gauge) and the bow runs with excellent lift in smooth water. In a chop the boat runs flatter with less trim and you can feel all the air going under as it skates along, with a bit of chine walk but never scary. Its a very exhilarating ride and loves to get airborne and comes down like a feather almost any which way you land, not like some of the bone-jarring landings in the cigarette that make you feel like you broke the boat maybe. I have done some absolutely nuts rides and am always amazed how tough it is.
From what I can tell the props are running right on the surface and don't aearate unless I use almost 50% trim on the gauge. When setting the boat up, we positioned the engines so that they would fit under the hatch to keep a clean look and for the occasional tanning session, etc, which just happened to be the factory recommended 14" X dimension. Its a tight fit back there, both X and Y.
I have seen the debate over singles and twins for the 30' Fountain. The Superboat beam is only 6.5 feet. It sure is a great handler but I would like to see almost 80 if I could. At 5100 RPM the Mirages feel like just a bit too much prop, as at that speed, 68 or so, the boat finally feels like its getting up on the keel and passing a nice air cushion underneath. The Hydromotives were very efficient out of the hole, obviously, but felt like a brick wall at 4800-5000, and slightly less speed. The cleavers spun up to 6000 but I was too busy driving back then to see a gps. The speedmeter is useless as all it does is get air into it and never goes above 50 or so.
The engines power curve declines slightly from 4000 up. The boat planes at only 2600RPM!
There is absolutey nothing on board or up front, its really light. I should be able to run a bit more timing advance, I think it was set up for 28 total degrees. Hard to imagine the engines being overworked.
So I would appreciate any suggestions to get me out of the 60's. My guess is with the extra weight in the back, the boat is pushing too much on the keel, so a prop that lightens the stern might be the answer?? What about the amount of toe/in or out on the bravos? Anyone that could guesstimate the optimum settings overall?....
thx
I have a 1982 Superboat that is rigged with 400 cube small blocks and Bravo 1.5's. The boat is a pleasure to drive and handles really big waves at amazing speed and flies very well balanced. I had a 35 cigarette and in some conditons it seems faster, getting "light" much more easily. That aside, I am trying to tune the boat for the best top speed I can. I have rev limiters set in the six area, open exaust, and well built engines. They dynoed in the 420 ftlb area last year and this year I am putting in roller cams for a few more HP. I have run three types of props over the years, 23p three blade cleavers, 23p four blade hydromotives (borrowed off the cigarette) and now I use 23p mirage pluses. I think I should be in the 70's with almost 900 HP out back but am stuck in the high 60's. I use what feels like a healthy amount of trim, (almost 50% on the gauge) and the bow runs with excellent lift in smooth water. In a chop the boat runs flatter with less trim and you can feel all the air going under as it skates along, with a bit of chine walk but never scary. Its a very exhilarating ride and loves to get airborne and comes down like a feather almost any which way you land, not like some of the bone-jarring landings in the cigarette that make you feel like you broke the boat maybe. I have done some absolutely nuts rides and am always amazed how tough it is.
From what I can tell the props are running right on the surface and don't aearate unless I use almost 50% trim on the gauge. When setting the boat up, we positioned the engines so that they would fit under the hatch to keep a clean look and for the occasional tanning session, etc, which just happened to be the factory recommended 14" X dimension. Its a tight fit back there, both X and Y.
I have seen the debate over singles and twins for the 30' Fountain. The Superboat beam is only 6.5 feet. It sure is a great handler but I would like to see almost 80 if I could. At 5100 RPM the Mirages feel like just a bit too much prop, as at that speed, 68 or so, the boat finally feels like its getting up on the keel and passing a nice air cushion underneath. The Hydromotives were very efficient out of the hole, obviously, but felt like a brick wall at 4800-5000, and slightly less speed. The cleavers spun up to 6000 but I was too busy driving back then to see a gps. The speedmeter is useless as all it does is get air into it and never goes above 50 or so.
The engines power curve declines slightly from 4000 up. The boat planes at only 2600RPM!
There is absolutey nothing on board or up front, its really light. I should be able to run a bit more timing advance, I think it was set up for 28 total degrees. Hard to imagine the engines being overworked.
So I would appreciate any suggestions to get me out of the 60's. My guess is with the extra weight in the back, the boat is pushing too much on the keel, so a prop that lightens the stern might be the answer?? What about the amount of toe/in or out on the bravos? Anyone that could guesstimate the optimum settings overall?....
thx
02-06-2007, 11:58 AM
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Re: 30' Superboat w t400's needs prop advice
hi i had three of the first 30 superboats ever made,the first
was overdose twin 235 outboards then three 235,then twin small blocks,400 hp each, that boat was called superdose,then i had a single big block 30,the first boat run 68mph,non counter rotater,the triples ran 72 mph,super dose
ran 84mph,and the single big block ran 70 mph,you should be
in the 70s to 80 you need help,
ron barrette, now i have a 40 skater called maxedout
that does 160mph call me i can help
was overdose twin 235 outboards then three 235,then twin small blocks,400 hp each, that boat was called superdose,then i had a single big block 30,the first boat run 68mph,non counter rotater,the triples ran 72 mph,super dose
ran 84mph,and the single big block ran 70 mph,you should be
in the 70s to 80 you need help,
ron barrette, now i have a 40 skater called maxedout
that does 160mph call me i can help
02-06-2007, 09:24 PM
#3
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Re: 30' Superboat w t400's needs prop advice
I cant say enough good things about the revolution 4's. they're more for the hp of a small block, not the torque of a BB.
I have a 26 Sutphen 520+/- horsepower, twin small blocks, wider than you, but a heavy tail ,too... seeing high 60's low 70's...I think your motors would spin the 23p's better than mine..i should probably have 21's..i would bet you'd see high 70's..at least.
post your Q in the props section..lots of good advise to be had there..
I have a 26 Sutphen 520+/- horsepower, twin small blocks, wider than you, but a heavy tail ,too... seeing high 60's low 70's...I think your motors would spin the 23p's better than mine..i should probably have 21's..i would bet you'd see high 70's..at least.
post your Q in the props section..lots of good advise to be had there..
