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Diesels for boats

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Old 04-06-2008, 06:11 PM
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So what if we had a 550 hp engine with 1100 ft lbs of torque and a 2 speed tranny would that break 110 in a 36' cat ?
Single engine? No way. Joe is right: You need the horsepower to make top-end speed. Efficient cruise speed is a whole 'nother issue.
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Old 04-06-2008, 06:13 PM
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Single engine? No way. Joe is right: You need the horsepower to make top-end speed. Efficient cruise speed is a whole 'nother issue.
Damn physics
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Old 04-06-2008, 06:14 PM
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i meant 2 engines
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Old 04-06-2008, 06:16 PM
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Originally Posted by HabanaJoe View Post
I would ask you are the speeds at which you want to run in the 50-60's? That seems to be the barrier, above those speeds you need the Hp and overdrive gears to get it done.
You need the horsepower to run in the 50-60's, too -- but the horsepower you need is only about 1/3 that you need to run 100. If your diesel swap is more than 1/3 the horsepower of the original gas engine, then you can re-gear to run efficiently in the 50-60'2. You can't re-gear to run 100 on 1/3 the horsepower.
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Old 04-06-2008, 06:17 PM
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I'm going to brow beat you watch out!!!!

Your 525's swap out what happened to top speed?

I agree with everything you've said.

I would ask you are the speeds at which you want to run in the 50-60's? That seems to be the barrier, above those speeds you need the Hp and overdrive gears to get it done.
Lost 8 to 10 mph on top, I think I can get a couple more mph but right now it's running the biggest propellors/lowest gearing they make. cruise at 56 with one person or six, makes no difference.
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Old 04-06-2008, 06:19 PM
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i meant 2 engines
Oh. Two engines, proper gearing, right props, surface drives, good hull, and you've got a real shot at 110 or better -- especially if the boat could already do 110+ with a pair of 550 hp gas engines, single speed tranny.
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Old 04-06-2008, 06:21 PM
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stainless,

Your question is will one or a pair of 2,700 rpm diesels making 550 hp push a 36' cat at 110 mph?

If you say a pair, I have to tell you damm close to it.

Real world example, the boat that Stefano was killed in was a 40'er. When she was Kappa Shoes in an earlier life with twin 600 hp Seateks she could run a little over 100 mph.

A 38' V bottom with worn out 600's could run just over 90 mph all day long.

Kappa was no where as effiecent or light as a Skater or MTI, I believe whole hearted with electronic controlled real 550 hp diesels and proper gearing 100 mph plus is easy, 110mph I just don't know?

haxbyspeed,

I bet if you can gauge the amount of hp those engines are making you'll find your not near the max. You hit that wall and need more prop speed to go faster, Once you get taller gears coming on plane will be hard and you prop down and still get any faster - that is where two speeds come in to play or some form of slipper trans.

Last edited by HabanaJoe; 04-06-2008 at 06:26 PM.
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Old 04-06-2008, 06:32 PM
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I like the direction marine diesel technology is heading but I gotta think it's going to be a LONG time before dealer support, affordable parts, parts capable of handling 1800#s of torque, and the high initial expense will make them any more attractive then the multitude of gas options...
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Old 04-06-2008, 06:44 PM
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300-400 hp diesels are comprable to 600-800 hp gas engines,its all in the torque
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Old 04-06-2008, 06:46 PM
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dmaxx,

Not to fight but show me the math or a real application that proves that, don't just make a statement - prove me wrong!!!
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