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Prop for 80hp merc on 89: 15ft bayliner capri

LilSkipper

New member
I've researched and finally come down to asking. Have an 89 Bayline Capri that I put a 1979 80hp Merc Thunderbolt on the back of. I'm hoping to get a final answer that would be best prop choice. Im aiming more for top speed and will be doing no towing/watersports with boat. Any input/recommendations are greatly appreciated!
 
No chart you can look at that will give you anything more than a starting point.

Only sure way to "fit a prop" is to find out what your max rpms are running wide open with whatever prop is on it now and adjust from there.

Every motor has a Wide Open Throttle range - normally a little above and below about 5500 rpms (but some vary).

If the WOT range of your motor is say 5200 to 5600 (as an example) and your current prop is turning it at 5000 rpms (max) you have "too much" prop pitch. Reducing the pitch by 1 (say 19P to 18P) that would (generally) increase the rpms to 5200 - a 1" change results in 200 rpms change.

That would be at the low end in my example so dropping 2" (19P to 17P) would increase the rpms to 5400 - smack in the WOT range (if you see what I'm talking about).

You can't get "more speed", at least not that you will notice, if you are propped "correctly" to start with.

If the motor is running in it's WOT range with the boat operation how "YOU" use it, loaded with your typical load that's as good as it gets.

YES - more pitch can result in more speed - but not if your motor can't turn that extra pitch. If the motor operates below it's WOT range when you have the throttle buried, then your motor is heading for an early grave.

So if speed is your goal get rid of every extra bit of weight you can and go for a prop pitched as high as you can turn without dropping out of your WOT range. And if that isn't fast enough, then it's time to repower.

Sorry, didn't really answer your question because there really is no answer.

If Bubba has the same boat/motor but always runs "heavy" with 4 passengers and Jimmy runs light all by himself and you are somewhere in the middle all three of you could be running different pitch props because that's what each boat "needs"...
 
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