wot

[Whitetail15]

do you guys run your boats at wot to get one end of lake or just trying to get somewhere.

manual says 4000 rpm max for any periods of time. mine will tach at 5400 at wot. i never ran at max rpm for more than 10 seconds just to see max speed.

4000 rpm in my 196 is about 37 mph.

[GoBig]

I only run WOT when the engine is fully warm and generally not for more than 30 seconds or so, similar as you. It's in my DNA -- I grew up with a Dad who was paranoid about running his boats WOT, "engines aren't made to run at 5,000 RPM!" he would yell at me when I wanted to romp on it. Then again, the Model-T was still in production when he was born so he hasn't quite grasped the evolution of engines. I digress. In any case, I guess part of that stuck with me so I keep it to a minimum. I'm interested to read some other perspective though...

[seth]

The only time I do is when I have full ballast and im getting a rider up.

[AirTool]

The only time I do is when I have full ballast and im getting a rider up.

What is the rpm for this case?

[DanielC]

I would avoid 5400. About 5000 is the max RPM you should run. Reality is, you gain a lot more speed, with a 500 RPM increase from say, 3500 to 4000 than you will get from 4900 to 5400. That should tell you the additional RPM is just basically thrashing the water, and not really generating more speed.

The RPM based stresses on an engine increase with the square of the RPM speed.
Twice as fast, four times the stress. Three times as fast, nine times the stress.

The most stress actually occurs at max RPM, as the throttle is closed. No gas pressure holding the piston down, and it actually rides up a little higher in the cylinder. The piston is moving the fastest about 75 degrees before and after top dead center. From 75 degrees BTDC, with a closed throttle, or on the exhaust stroke, the crankshaft, and connecting rod are actually being pulled by the piston, as the piston is slowed from its maximum speed to a dead stop, at TDC, and changes direction.

I am not afraid of running WOT. Even up to around 5200 RPM, on a GT-40. My engine has 2319.4 hours on it. But I do try to avoid prolonged running above 4200.

[IMPACT-EV1]

if you have a stock motor with prolonged running at 4500-5000 especially if you changed the props with a lesser pitch typical of a boarding set up, then you might have some issue. Now if you have a motor that is built Like I had then you can run at 5500 all day long if you want and I did and why I had the motor balanced.