Why go easy on it when coming on plane?
 

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?

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

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

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

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.

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.

action : smash throttles wide open
reaction : broken drive :whistle:

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. :picard1:

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.

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.

not really, the point of throttling it is to keep the props spinning at the speed needed to keep the boat going the same speed, roll out and roll back in. that way there is no harsh loading or unloading. if throttling (proper) was causing any damage then why would anybody do it? might as well just install rev limiters and let them fly unless your the guy from that fountain video.

Lol

The outdrive has to be the worse device ever designed for the transition of crankshaft rotation to propeller.

If this was FB, I would "like" this statement.

my boat stands straight up and drags for ever if i dont role on the throttle pretty quick. Now I dont just slam them down. I dont know if it is my pitch or what but when i got the boat i tried to bring it up slow and it just didnt want to go. the bow came up so high i couldnt see and sounded like the props where just sliping. I am running bravo x drives with 28p 4 blades. to me it seamed harder on the drives and motors then rolling the throttles up quicker to get it up on plane.

Here’s one very good reason not to hammer the sticks out of the hole. When you’re idling, your hull acts as a displacement hull. That is, it displaces the water in front of it to move forward. As we all know, displacement hulls (blow boats, tugs, aircraft carriers) are not very efficient – because there’s so much resistance.

Once your hull comes up on plane, resistance drops dramatically since it is now riding up and over the water. But, the transition from displacing water to riding up and over it consumes a ton of power to overcome that resistance.

So coming up on place involves overcoming some serious resistance. Sure, one could simply hammer the sticks and overcome the resistance through the application of brute power. But, since water is basically incompressible, all of that resistance is going to show up somewhere. One place is pressure against the hull. A more important place – for the purposes of this discussion – is the bearings, gears and other load bearing surfaces in your engine and drive. Do you really want to spike the pressure curve and hope your driveline lubricants can survive the attack or maybe spread the force out (and reduce it) over more time?

Same goes for throttling a boat in rough water. Folks who think the sticks should be operated like toggle switches (like the guy in the Fountain at LOTO) tend to break a lot of stuff. Why? Back to the incompressible stuff you’re floating in. (See Glass Dave's post.)

Many boats require “significant throttle input” to get up on plane. Heck, mine comes up pretty slow because the lawn care device on the transom is cranked up so far on the jack plate. But, one doesn’t need to slap the sticks to get to full throttle. In fact if I ease into it, although it may take me a bit longer to get up on plane, but it actually takes less throttle. And there’s significantly less stress on the driveline. If I simply hammer it, all it does is try to burn a hole in the water.

"lawncare device on the transom" thanks I needed that laugh! I think I just pissed my pants lol

I just put the sticks all the way forward then pull them back an 1/8th of and inch because i heard wide open is bad

We are in the same boat you are (no pun intended). unless the sticks go up towards the dash and hit around 3800 RPM, boat ain't coming on plane. we have a lot of nose lift and we will keep slipping unless its pushed to a higher RPM. Tried tucking the drives and messing with the tabs...no better. Just put it on the wall!!!!

have you tried putting the tabs all the way down ? Also it's different when the props are slipping, the 382 needed a quick blast of throttle to get going but could roll back as the props started to bite and not load the drives so hard

yea tried with tabs all the way down...I wouldn't say we put the throttles on the wall but slowly build to 3/4 throttle...as it bites slowly back off.

My guess the slower you go on plane the longer your dives will last?

OK - Lots of good replies, and lots of different situations and setups. In my case, I get almost zero prop slip coming on plane (DuoProps) and, given that the engines simply don't make a lot of torque at those low rpms (2500-3000), I guess that can get away with WOT.

I would think that by far the worst thing that would happen would be leaving the water, allowing the engine to rev up to the limiter, and then landing with the throttle still wide open. At that point, you ARE dealing with the engine being at peak power, and the prop being hooked up.

I guess my question is more like: Why would the drive care how fast it is going? All it should care about is the force (torque) being applied to it, and therefore the force that it is applying to the water.

The best point raised so far is: Why do we have to put up with drivetrains that WON'T handle WOT? We'd freak if this was the case in our cars.

I had a bravo 3 on my stingray with a 310 hp 454, i managed to twist the propshaft pretty bad on that be careful with any power you have

"like"

I have mentioned this in other threads also. I also don't understand the "myth" on how getting on plane slow and easy is less harsh on the drives?

How does X amount of torque applied through the drives for XXXXX amount of time worse then the same amount of torque applied through the drives for less then half the amount of time??

There are a TON of boaters on this site that BABY their drives getting on plane and STILL blow drives. Have any of us tried the opposite and see if they break?

And when our drives break it NEVER happens while getting on plane anyways

Not saying that slamming it in gear and mashing the throttles instantly is good.

Just move them forward smoothly, but not to slow not to fast, then back off when the RPMs start increasing.

You can move them forward smoothy and slow and just sit there halfway on plane for 10 min also, might as well just put the forward a little more and a little faster and just get up and be done with it.

Biggest problem is ALL of our info are just guesses. We really have no clue and no way to actually test which way is the best.

how many pounds is applied to the scale when you jump on it? now step on it slow and easy. same 200lb guy can have quite a difference in load applied. And the load is quite different, applying full throttle while under full load is easily the most torture a drive could be put through. Less throttle = less torque. Less torque and less load "should" extend the drive's life

but how much torque does the engine make at what RPM? The engine can be at full throttle but not be appling maximum torque

and again, how does X amount of Torque applied for 30 seconds better then X amount of Torque applied for only 15 seconds?

As far as torque over time that's a good question, bet some interesting theories come out of that one!
At full throttle the engine will be at its torque potential for a given rpm, back the sticks off a bit and the same rpm ( up to a point) can be achieved without making as much torque. Or at least this dumbass thinks that way lol

My opinion is drive it anyway you want if you can afford to fix it.

no one has mentioned inertia. The end power would be the same getting on plane and running wide open so that has nothing to do with it. But taking the inertia of the engine spinning with full power and slowing it down in a short amount of time puts alot more load on the drive then running wide open.

I bet this theory could actually be tested. I'm not an engineer but I see it like this, it's not just the torque that the motor makes that would hurt the drive but also what's going on at the other end. So factors like weight of boat, drag coefficients on the hull at the time of planing, and bite of props would be equally as important.
I bet if you had enough time with a prop shaft Dyno that you could adjust the amount of load on the shaft you could simulate planing and find out which way was easier on parts. But more importantly exactly what amount of force begins to cause fatigue on drives. Now it's late and I might be a little delirious, but Let's say you could figure out this magic number for each drive and take it one step further. Why not design a shear pin setup on either the input or output shaft of the drive, you hit your max load amount the pin shears you replace the pin but save the drive? So it ruins your day, but anyone who's grenaded a drive knows by the time you get parts or somebody to fix it it's always at least a week or more.
I wonder if that would actually work?

If I mash the gas in the cat it will dig a hole and not come up u have to come up slow or it will not plan with the big props , the small props u can mash them and lett it eat! Like a drag boat:)

For me I don`t need a scientific explanation, its just common sense. There is no doubt a drive is under a ton of stress trying to get a boat on plane with the throttles mashed.

I`ve blown up enough rear ends at the track to know if i throw on a pair of drag radials and hot lap it ..it`s going to fail a HELL of a lot faster than taking off easy from a stop light.

& we have a winner!!

I'm just a dumbazz but here is what would seem obvious to me.

Even if your peak torque is in the 4000-4800 range of your engine is freewheeling (in neutral) there is no resistance to it, thus it is not developing torque then. Only under load can torque come in. The most resistance you drivetrain experiences is when there is the most resistance which happens at the point your trying to get on plane or at top speed if your propped right and don't overspin your engines.

Before I ran #6's (which are a godsend after you are use to any Bravo's) EVERY time I poped a drive was on getting on plane, I'm taking gears breaking lower/upper, casing blowing up, top cap detonating, shaft breaking...M-O-U-S-E... get it, So that is enough for me to take it easy on take-off if you want to limit your wear...

My very humble opinion.

PS: I'm surprised you ask that CSpray you know the answer unless your just bored and figured rightfully that it is a good educational discussion to further mankind in broadening the knowledge base as a whole,,, to a population that makes it so the Kardashians (however you spell those fat chicks name...) are marketable...

It just happens... Pop goes a #6 drive...

[YOUTUBE]http://www.youtube.com/watch?v=FaYSDK4FXj4[/YOUTUBE]

...It even happens to the best of us...

http://en.wikipedia.org/wiki/Penske_PC-23


http://limestonedev.com/images/boat/laughing.gif

It becomes the case when you build a "go fast" car. Take any performance car you like put it on slicks and go drop the clutch at 4500rpm. See how the drivetrain holds up. However it is fairly inexpensive to do a 9" rear an keep a spare 3rd member handy. You don't just have a spare drive in your cabin for when it does pop.

Anything put to the ultimate will fail. Some faster than others. Take a boat with 350/260 and an alpha. Not very fast but that alpha will last a very long time even after repeated hole shots. We used to use ours to ski all te time when I was a kid.

Ultimately the more you beat on it the faster an more likely failure is.

Great post! Everytime i look at my broken one sitting in the garage i think this very thing. Another thing is why the hell are they so expensive? Is the marine "tax" really that high? I look at any of these drives and i just dont see the money sitting there.

Not all of us who wonder if getting on plane slow feel to get on plane fast you have to MASH the throttles all the way hard and fast.

YES< if you slam your sticks you will break something

But what about just SMOOTHLY accelerating but to a higher point so the boat gets on plane a little faster without dragging Azz forever?

Guess thats where I am at.

SLOW is bad
SLAM the throttle fast and hard bad

There prob is a "sweet" spot for every boat, and i don't feel super slow is correct for my boat because it still just plain WEARS out the XR gears no matter what. Might as well just get up on plane and enjoy your day.