88 MACH 1

How do you know what your boat can handle? Speed and HP I mean. All these HP parts available and repowering, how do you know when what you power you boat with is too much and could become dangerous? Later, 88 Mach 1

mopower

88,
I'm not sure anyone can answer that unless they've had experience with the boat your talking about. I put a 540 (625hp) in a 21' FourWinns Liberator Calm water , the thing was a rocket . Sloppy water you had to repect it and keep it under control (speed that is) , because it really felt like you were on the ragged edge . I put the original BB in it before I sold it.
Didn't want any law suits for injuries sustained .

Remember , you can put all the horsepower in the world in your boat , but the boat only gets to use what you give it with the throttle.

Six Leg Dog

1988 40 fountian + twin 900SC's = one dead best friend,,,,,,,,,,,,,,

88 MACH 1

Yes It is a tuff question. All I can figure on is the drive. Was told not to run no more than 500 hp thru a Bravo 1 if you want to be using your boat more than rebuilding the drive. I know others have run more hp thru a Bravo 1. Well, be safe. Later, 88

Griff

Its going to depend a lot on the driver and boat set up too. You've got to know when it becomes unsafe. I know in my 24 Outlaw, it takes a LOT of trim to get top speed and the boat gets real loose if you're not real careful and it only runs about 65. If I get a big crosswind gust while trimmed all the way up, it can get real squirrly in a hurry unless I get out of it and trim down. This is with a Mirage Plus prop. With Bravo 1, I loose a couple mph but it keeps more boat in the water and stays hooked up a lot better and isn't affected nearly as much by the same cross wind.

mopower

88,
Yeah , I too have heard 500 hp on a regular Bravo is safe. If you treat them right you can get away with more. This means no straight arm hole shots and no "catching air". That splash down is really tough on the whole drive train .
Believe it or don't , I put that 625 Hp 540 in my Liberator though an OMC King Cobra. I followed those simple rules above and had no problems. That was summer of '99 , the next owner is still running the same drive but with the stocker in front of it and no probs .

GEOO

Any Speed can be dangerous in a car or a boat.
Most people have this idea boat's can go full speed most of the time. Fast boat's are not much different then fast cars. You have to respect the speed. You don't drive 100 mph on a curvey back road with your car so why would you take hard turn's your boat at high speed's.
Most V Bottom's were designed to go fast; as fast as the designers could make them go with the available power. They don't have a built in hull speed. Your set up of drive, weight(CG), tabs, prop selection, ect control the speed and stability of the boat.
A stock 18 foot Deep Vee with 300hp is stable at 60 mph, chime walks at 65-70 when trimmed up. Increase the power to 400hp you can drive 65-70 fine, trim up to go 75-80 you get chime walk, Play with the set-up and you may eliminate the chime walk.

88 MACH 1

Basically wondering when will boat's hull just give up. They make car tires speed rated for a reason. Just looking for someone to say like " At 1000 hp or 100 mph a Donzi hull will fall apart" Just an example. Later, 88

GEOO

Any boat will fall apart if you beat on it hard enough. They have no speed limits just keep an eye on every thing. If you get stress cracks showing up, repair them!!

mcollinstn

Car tire speed ratings are based on heat. A tire carcass will get hot at sustained high speeds. Particular belting materials and belting designs along with different rubber compunds and carcass thickness will make a tire stand up to heat better. Problem is, with old technology, the tires that would stand up to the heat rode like cr@p and were too stiff. New technology offers compliant ride and good temperature tolerance but at a higher price.

So today you can buy cheap highspeed tires that ride bad or expensive highspeed tires that ride well....

No boat will just fall apart with too much power.

Boats are essentially flexible. Big power on smooth water is easy on the hull and can be tolerated way past design limits on a particular combo.

Stock power on rough water overtaxes many hulls and causes structural problems, delamination, etc..

I've run a 16' outboard runabout over 95 mph with more than twice the max horsepower rating on it. Boat was designed for speeds in the mid 50's with a 110hp or less outboard. Had a massaged 2.4 merc on it. Smooth water was fine. Rough water broke the stingers out of it.

At a given water condition (light chop, etc), the faster you go, the more flexing a hull will have. Just like tires, the faster the hull flexes the more heat build within it and at a point, delamination or microcracking will start. There is no actual speed rating on a fiberglass hull, but there is certainly "design speed".

A hull run way over design speed will become unstable. Some guys (me) get a charge out of driving an unstable hull...

Like Geoo says (and he knows since he is driving 50% over his hulls max design speed), regular inspection and a bit of common sense are the best guidelines...

(maybe he is 60% over..)