prop question

[boatman37]

so last year i was hitting 4000 max RPM at about 33-34 MPH (GPS). I have a 1986 Sea Ray Sundancer 250 with a Merc 260 Alpha 1 Gen 1. The manual says 4200-4400 max. RPM and about 32 MPH max. Thinking about buying a new aluminum prop. Current prop is a 14.5x17 aluminum 3 blade. The paint is all flaked off and it is bare aluminum now but not sure that would affect it? No idea how old the prop is or if it has ever been hit. I'm not concerned about top speed (haven't even tried max RPM yet this year). More with cruising speed and getting on plane. It planes out nicely now and I can stay on plane at about 24-25 MPH at about 3200 RPM. At about 3500 RPM I am at about 26-27 MPH.

 

[Scott Danforth]

we need maximum WOT RPM and speed when trimmed out

 

[Sea Rider]

If max wot rpm is 4400 and achieved 4000, there's a 400 wot rpm difference. 2 less pitches shouldd pull wot revs towards 4400 if Rule of Thumb applies ( +200 wot revs per one less pitch) Your hole shot wil better slightly more, but top end speed will decrease a bit, or buy a new exact current prop. You decide.

Happy Boating

 

[boatman37]

last year max was 4000 RPM at 33-34 MPH (tried on a few occasions). should still be the same but haven't actually tried it this year

 

[Sea Rider]

If engine is still 100% healthy should dial same wot rpm with same used or exact new prop, if revving to 4400 with a leess pitch prop, should loss 2 MPH, only checkable on a wot run as loaded. What do you preffer, slight more top end speed or slight better hole shot, both with their own pros & cons.

Happy Boating

 

[boatman37]

not concerned about top speed. holeshot is good but better wouldn't be bad. we don't do any watersports with it so pulling skiers and tubers isn't a concern. so in theory a 14.5x16 (current is 14.5x17) would raise my RPM by about 200 but lose slight top speed? and give a little better holeshot?

do you think having all the paint flaked off of my current prop is affecting it?

 

[Sea Rider]

Yep, one less pitch pulls wot revs higher, what you can do is send current prop to a prop shop and have it re pitched from 17 to 15, with a 16 will thoretically gain just + 200 wot revs. Or buy a new 15 pitch prop in whichever diam comes factory delivered.

Happy Boating

 

[boatman37]

Thanks!