C_Spray

For the sake of conversation:

It seems to be gospel that bringing a boat up on to plane at WOT is one of the most abusive things that can be done to a drive. While this makes sense on a street car, where the transmission multiplies the torque to the final drive gear, virtually all boats are top-gear-only. Add in that most engines develop peak torque well into their rpm range (let's say 4000-4800 rpm in general) and that prop slip rate is much higher at low speeds, and it seems to me that peak drive stress is more likely to occur at speed when the engine is at peak torque and the prop is hooked up.

My engines develop little torque below 2500 rpm, so full-throttle starts are pretty much mandatory if I ever plan to get up on plane.

Am I missing something in the physics here?

professor_speed

I would think it has more to do with drag on the hull off plane, and not the toque the engine is making.

Fenderjack

Our 32 fever has stock 340 carb motors with 25 3 blade props,1.5.1 ratio.It will come right on plane at 1750 RPM.Hole shots break stuff,unless you are running a small dia or a lot of pitch that will let you cavitate till your on plane before hooking up.Just my 2 cents. JOHN SR

smokin' gun

not everybody has 1 1/4 or bigger prop shafts . imagine this a 38 ft top gun with trs or bravo 1s and they built a ton of em close to 11.000 lbs on 2 little 1'' prop shafts can you imagine the stress alone on the shafts never mind the gear sets .thats why its best to get the weight moving slowly

Unlimited jd

As much as it's believed that a boats driveline has the same 100% load on it all the time it doesnt.
There are a lot of contributing factors. More hull in the water=more drag, all that drag and the engine pulling up to its torque peak is the problem. Part throttle and climbing rpm will only make so much torque. Significantly less than its max. Engines on the dyno are tested for power at wot all the way through the rpm range to see where max torque is, which can only be achieved with the throttle wide open. Easing up on plane allows the rpm to climb without quickly applying max torque.

kreed

An object in motion, stays in motion... Wait. For every action, there's a reaction. Uh...nope. Ahhhh....ok. I don't know the answer.

Unlimited jd

action : smash throttles wide open
reaction : broken drive

glassdave

I never understood people hammering the start either. Makes no sense to me in these things unless you actually enjoy wreck'in your stuff. I choose to break my stuff the old fashioned way, after its useful life has expired and not a moment sooner. Got a buddy of mine here that fire walls it every time he gets on plane, seen some absolutely grenaded drives hanging of his boat yet he still does not get it.

professor_speed

Boats are the only motor driven vehicle you cant slam the throttle, its sad actually.

Could you imaging buying a high performance "anything" and being told you can't pin the throttle until you are up to speed? only in boat does that fly.

302Sport

I don't hammer it getting on plane but I think that throttling the boat at 6000rpm at 120mph, in and out of the water, hundreds of times in any given day, puts a hell of a lot more stress in everything than hammering it one time out of the hole.