Prop question

[jmlloar]

My 20' is planing at 22mph and is at 4500 rpm at 31mph which seems slow. What prop should I use? It has lots of low end power but shouldnt it run faster than this?

It a 1975 888 mercruiser.

 

[Dhadley]

Re: Prop question

Depending on what type hull it is and the weight it could be OK. Or it could be horrible. Do you know the gear ratio of the drive? If we knew that and the pitch of the prop we could figure the slip percentage. That will tell us where we're at.

Is 4500 rpm your top rpm with an average load?

 

[jmlloar]

Re: Prop question

4500 at 31mph is top speed fully loaded. its a tri-hull.

It just seems a little slow for a V8. Its supposed to weigh 2356lbs

 

[kenmyfam]

Re: Prop question

What prop is on it now ????

 

[jmlloar]

Re: Prop question

no clue on the prop

what kind of speed would be normal for a boat this size?

 

[jaymasta]

Re: Prop question

no clue on the prop

what kind of speed would be normal for a boat this size?

my cousins 18' hourston has a 100hp yamaha, 15p prop and it tops out at 48mph@5800rpm

 

[crunch]

Re: Prop question

no clue on the prop

what kind of speed would be normal for a boat this size?

Where on the prop do you find the numbers? I've looked all over mine, in all light angels, and don't see a thing.... 1978 merc 800.