Ricardo said:
"In other words, if your engine cannot reach the OEM specified WOT RPM range, it will become over-burdened at all RPM."
Well, that's a bit misleading.
If you'll put your eye glasses on and read what I typed, you will see that it's not misleading at all.
I'll even loan you a pair.
The engine is ALWAYS under load at ALL rpm.
That is very true and is most likely understood by most all members.
What I was referring to was "over-burdening" the engine if it is not able to reach the WOT RPM.
It's not over burdening to have an over-pitched prop spinning at, say, 2 or 3000 rpm. You just won't be very efficient.
A Marine Engine that is performing Inefficiently (due to being over-propped) would equate to a reduced life span.
The engine will run out of horsepower too soon with the higher pitch
so it's not gonna wear out the engine or anything, you just won't be able to go as fast as you could with the proper pitch.
It may not wear out the engine on that particular day or week, but give it a full season or two, and report back to us.
It's like gearing in a car.
Also, it's not really a science it's more art.
Call it what you want to. For a very good reason the OEM Engineers have determined a best suited WOT RPM for given engine.
It's right there in the OEM manual, and it's often printed somewhere on the flame arrestor.
In order to get the correct prop dialed in you're supposed to test various props over a measured mile on flat water with no wind and the tanks full. This involves swapping propellers, testing, swapping, testing, until you hit the perfect one.
This is why the OEM Engineers suggest a WOT RPM spec.
It is also necessary to load the boat as you normally would while doing the WOT RPM test.
It would make no sense at all to prop it with a light load, and then expect it to perform well with a full and heavy load.
Nobody really has the time to fool around with all that so you take your best wild-ass guess.
If a person is not willing to take the time to prop their drive correctly, when will they find time and budget to replace a very expensive engine after it fails or wears out prematurely?
Generally speaking your engine and drive ratio (assuming it's the King Cobra for small block not big block) can most likely do pretty well with a 14.5 diameter by 24 inch pitch propeller. If you're winding it out at 5K plus then you probably have a 19 inch pitch prop.
Just guessing tho.
I would suggest to the OP that he use real numbers, and not just take a guess at it.