Re: size prop to use for 1988 460 king cobra
can anyone tell me what original prop was put on an '88 omc 460 king cobra. I believe the wrong one is on mine right now. also what pitch would work best for rpm's running too high. it is a 7.5L thanks
Howdy,
Welcome aboard!
Your question is best asked in the prop forum. I am sure a MOD will move this thread for you.
Now, there's no real "original prop" for any particular engine and drive.
The It totally depends on what boat your engine and drive are installed in.
You will not know what to use unless you have some info on hand.
Accurate RPM. You MUST have a tach of known accuracy.
Accurate SPEED. GPS etc.
You must know your drive ratio. Your's should be a (if memory serves) 1.41:1 drive.
You must know your recommended RPM. (if memory serves again) 4200-4600 RPM. It will be in your original OMC owners manual.
Once you know these things, You select a prop that will allow you to obtain close to the upper RPM in the range (4600) at WOT (Wide Open Throttle) when the boat is loaded near where you will operate most, AND at the approx elevation of the lake you will most often operate.
My boat in my signature used a 14 1/2" 19p stainless steel prop that was repitched(cupped) to 20p. (I still have it too!)
I also have a 17p 15" stainless steel prop that was just TOO low pitch. It allowed the RPM to go too high at WOT... This was in my 21" Liberator.
A 17 pitch might be just right for a slightly larger boat.
You just don't know until you try something different.
Before you anything about props though you must ensure that the engine is running correctly, An engine that is timed wrong, or is worn out (poor compression, or other problems)may not make full WOT RPM with any prop.
Cheers,
Rick
