Prop help

[Billythepokerkid]

Recently bought a new to me boat. Took her out a few times and it seems to run pretty well. Just curious if I am over-proped. Boat is a Javelin 379 FS with a 1996 Johnson 115 Fast Strike. I am guessing the weight fully loaded is around 2200 lbs. Right now I am getting about 4800 rpm at wot at about 40 MPH according to gps. Im not really concerned about the top speed so much as the stress on the motor with the monster prop that's on it now which is a 4 blade 13.5 X 21. From my research it looks like I need to get revs up closer to 5500. Seems severely overpropped to me, but I am by no means an expert. Any help, opinions or otherwise wouldn't be greatly appreciated

 

[GaryDoug]

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[Billythepokerkid]

Yep that's what I meant, auto correct at its finest. The throttle is opening all the way checked that first. The carbs were cleaned and rebuilt and it was tuned up and synced. The prop looks huge on the motor. I was thinking a 3 blade 17 pitch perhaps?

 

[jimmbo]

2200 lbs is a lot of boat for a 115. Getting rid of one blade will bring the RPMs up even if you don't drop the pitch. I would think a 3 blade 19 would be pretty close to what you need

 

[GaryDoug]

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[Billythepokerkid]

That's about what I figured at 2200 fully loaded. With around a half tank and just myself it was right around 4800. The rpms don't really change based on the load. With 2 other people and the same amount of gas the revs were about the same, but I picked up a couple mph.

 

[Sea Rider]

Is it possible at a prop shop to modify actual prop pitch from 21 to 19 pitch, while maintaining same 4 blade prop. Wot revs should surely go up...

Happy Boating

 

[GaryDoug]

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[phillnjack2]

you need to get around 5800 to 6,000 rpm so as to know your not lugging the motor. anything under 5600 is going to kill the engine fast.
those motors go on for ever if propped right.
you get that 4 blade taken down to 19 pitch and have the half inch taken off the diameter too. it will wake the motor up real nice.