propping

[shdw134]

I know this has been addressed before but cant remember the thoughts. I have a 19ft. open bow, 5.7l motor, alpha one drive. Problem, at wide open throttle i am at 4800-4900rpm, which direction do i have to go in pitch to bring down the rpms? At this rpm i am acheiving 52-54mph. I want a good all around prop. Not real conserned about top end but do want good hole shots for skiing, and tubing, but also want at least a desent top end. Thanks guys,and gals

 

[achris]

Re: propping

These engines are speced at 4400-4800 RPM WOT. Why do you want to change? If you up the pitch (bring the revs down) you will only be increasing the load on the motor and gearbox (leg gears). This applies to the whole of the rev range, not just the top end. Are you happy with the performance of the current prop? If so, leave it. As my old granny use to say "If it ain't broke, don't mess with it!".<br /><br />Chris.....

 

[shdw134]

Re: propping

Yes chris i am happy with the performance of the boat now. I was just under the assumtion that the rpms were suppose to be in the 4200-4600 range. I am new to boating and want to watch evering close so i dont have bigger problems later, i am on a somewhat limited spendable income. Thanks again Todd

 

[Doug Durako]

Re: propping

Agree with Chris----prop baseline should achieve maximum RPM, then tweak from there if something is not to your liking (hole shot for skiing, mid range to plan, top end for speed).<br /><br />I am never satisfied, so I have three props. Depends on who is running the boat that day and what the activities are.<br /><br />With two 20-something kids, my boat gets a lot demands put on the motor on any given weekend.<br /><br />One prop won't do it all for me.

 

[Jdeagro]

Re: propping

shdw134;<br /><br />Do a search on Smart Tabs on this site. There is much more to performance and handling than prop changes. If you would like a tech booklet on "boat balance and performance" it is free. Just send your mailing address to info@Nauticusinc.com or call 800-233-0194

 

[magster65]

Re: propping

It's good to have a spare prop. When you buy one get one with another inche of pitch. This'll hit or be very close to the rpm you're looking for at WOT.<br />I'm going to get that boat balance and performance booklet too, it sounds like something everyone should have really.<br />Thanks nautiJohn

 

[achris]

Re: propping

I apologise, the correct Max RPM is 4200-4600. With yours running up to 4800-4900, I wouldn't worry, unless you plan to run at max revs for hours at a time. My 4.3LX (4400-4800) runs to just over 5000. It performs very nicely. As the prop is light loading the engine I don't expect to have much wear on big end or main bearings when I strip it. Probably in a couple of years, when it's done about 1300 hours. Also by propping high you're helping your engine deal with today's poor quality fuels.<br /><br />Chris..........

 

[mercrewser]

Re: propping

Buy a propeller with more pitch, the next size up. This should bring you into the rec. rpm range. This should make you and the manufacture both happy. Top speed and cruising speed will go up, hole shot may go down especially with alot of people. Your engine makes its rated horsepower at 4600.