Prop Size recommendation

[sebas54]

Hi I have a 1980 22.2 foot aquasport with a 4.3l I/O merc. I need a new prop. What prop size should I get?? Please if anybody had a similar setup, let me know what you used.

Thanks

 

[steelespike]

Re: Prop Size recommendation

Do you have your prop size and present max rpm and speed?

 

[sebas54]

Re: Prop Size recommendation

It had a 15.25 x 15 prop and went 27mph at 4550 rpm.

I just bought a new prop 16 x 14 and it went 23mph at 4850rpms.

Thanks

 

[Bondo]

Re: Prop Size recommendation

Ayuh,......

Either due to your Motor not making enough Power,.....
Or,...
Your Hull is Waterlogged,.....

It Appears that you Can't turn more than the 15" prop......

 

[Dandelion]

Re: Prop Size recommendation

Your rpm's are right about on the money. But with a 14" pitch prop?? That is weird. I can see a 14" pitch prop only making 23 mph with your rig. But I'd have guessed the engine would be way over-revving.

I'd say either your tach is off, or, more likely, something else is not right: engine compression or the boat is waterlogged, for instance.

A 22' boat with a 4.3 Merc ought to do about 35-40 mph at 4800 rpm's, with a 23" pitch prop. But that would be a new boat. The wild card here is that it's a 28 year old boat. Any number of things could be off. You might not achieve ideal figures no matter what you do. That's not a disaster. Most important is to have your boat operating at the upper end of the recommended rpm's at "Wide Open Throttle".