Wrong Prop Size? Please Help ANYONE

[MSmith3615]

I recently had my boat in the shop for some repairs. The shop had my boat alot longer than they had told they were going to have it. So when I went to pick up the boat the service manager told me he was going to give me a new stainless steel prop. After I left the shop and got home I noticed the prop was a 14 1/2 dia 17 pitch prop. I think it should be a 14 1/4 dia 17 pitch prop, so I called and asked him about it and he told me it was the right dia. My two other props I had were 14 1/4 dia. I'm pretty sure 14 1/4 dia is what is supposed to be used. Can this cause problems? Or affect performance? Please help I just spent 2300 and this boat and I don't want anymore problems. The boat is a 21ft cuddy with a 1985 merc 260.

 

[olbuddyjack]

Re: Wrong Prop Size? Please Help ANYONE

Should be fine. Theoretically the extra quarter inch should give you a little more bottom thrust but I doubt you notice it. Stainless doesn't flex as much so you may notice a difference from that. Put it on and see what it does. If you can hit max rpms at wot it wouln't hurt a thing.

 

[Bondo]

Re: Wrong Prop Size? Please Help ANYONE

Prop Diameter is determined by the Engineer that designs the Prop..........<br /><br />It's something that You have little control over,...........<br /><br />You don't say What outdrive you have,....<br />But,....<br />Mercruisers can,+ Do run props from about 14"s to 16"s.......<br />Depending on the Design,+ Materials used............

 

[MSmith3615]

Re: Wrong Prop Size? Please Help ANYONE

Thanks alot experts, it is a mercruiser alpha one, I believe. I know its a mercruiser just don't know if alpha one or pre alpha. Its the same year as the engine 1985.

 

[canufixit]

Re: Wrong Prop Size? Please Help ANYONE

Prop matching to a boat is an intersting read - if you get a chance go to the Mercruiser manuals, prop manuals, etc. ... take a look<br /><br />But in short - you need to match the performance needed (Tug, or speed; Ski boat or high speed, etc.). Pitch and prop diameter can be adjusted to this - while ALSO keeing the max end RPM is the sweet spot. For Those of us in the North - there is even a difference betwen "summer" hp and "Fall" hp (Humidity in the air reduces the Qty of Air available for a given qty and hence HP will drop - and you may beed to change the prop to re-gain the RPM drop ...<br /><br />Alu Props will bend - so it does help on take off (Bending of prop is like changing the pitch) - changes to Pitch will change the rpm (mine is 400 RPM for each 3" pitch - 120 Mecrcruiser.). In short - props are like a dance - but you need to know the music you want to dance to and then choose a partner ....

 

[f_inscreenname]

Re: Wrong Prop Size? Please Help ANYONE

You probably want to play with this. http://www.boatramp.com/prop_applet/PropAnalyzerAppletG.html

 

[vipzach]

Re: Wrong Prop Size? Please Help ANYONE

That link is pretty neat and pretty accurate. My boat runs 4500 rpms at a little over 35 with a 17p prop, just like that chart says. Makes me want a 19p prop to go faster, but don't want to lose my hole shot. Damn dilema!!

 

[f_inscreenname]

Re: Wrong Prop Size? Please Help ANYONE

I try to pass it on to everyone because it is very cool and free. Its also right on with my boat.