19 vs 23 P on mercruiser 4.3

[nysono]

Did a little research on Michigan wheel prop finder and they suggest a 14 x19P aluminum or SS prop for my boat. Currently, from dealer, it has a 14 x 23P aluminum (unvented).<br /><br />Seems to me there is a huge difference in 19P vs 23P. What is everyone else running<br /><br />BOAT SPECS:<br />2005 bayliner 195 runabout<br />4.3 mercruiser/ alphaone<br />current rpms at WOT about 4300<br />current top speed at WOT is 45-48 on speedo, havent done GPS run yet<br />just installed smart tabs.....on plane in no time now.<br /><br />Thanks<br />Steve

 

[Dhadley]

Re: 19 vs 23 P on mercruiser 4.3

If I remember right, and I probably don't, the top rpm's on a 4.3 should be about 4600. Something keeps telling me maybe 4800. Either way you could use some more rpm. Unfortunately with a stern drive it isn't all that easy to raise the motor so we're kinda stuck with the current X dimension.<br /><br />Going to a lower pitch should bring the r's up a bit. In doing so we'd want to get as much lift out of the prop as possible. <br /><br />A prop with less pitch will gain rpm but possibly slow down on mph. A prop with more lift will reduce drag and keep the speed and rpm up.<br /><br />If we could raise the motor we'd gain rpm and speed both and stick with the 23" prop. Our best bet may be to try a good 21 or 22 and see what happens.

 

[nysono]

Re: 19 vs 23 P on mercruiser 4.3

thanks for the info. Yes recommended WOT RPM max is 4800. Im not all that worried about top speed just wanted to make sure I wasnt over pitched and in some way damage the engine. Need a new prop anyway (found a sandbar last year) and wanted to get the best one for the set up I have.

 

[maxum1800]

Re: 19 vs 23 P on mercruiser 4.3

Just a note about the prop choice. I recently bought a 94 Maxum 18 foot bowrider with a 4.3 and it had a 19p aluminum prop and My r's where way too high. Iwas told that they put it on for pulling multiple skiers? Anyway I could not plane from a stop,stood it right up for the longest time and then when it did plane I had to back off the throttle at 5000 rpm before reaching top speed, at that point I think I was at around40 mph. I did some questioning and was told that I should have a 23 pitch prop so I located a regrind one for 75 bucks and i am in the ball park now. Planes fine and quick and top speed trimmed out was 49 mph and my engine rpms are 4900 max so I'm happy. I think with your specs I'd try a 21 pitch if anything so you don't run into over reving. I think that you may want to do something as your r's are low at 4300 if your all trimmed out because you could have pinging at that load and not hear it and thats not good either. My 2 cents,by no means an expert. Tom