'93 Johnson 115 prop help

[bhmdorf]

I have a '93 Johnson 115 on an aluminum 22ft Lowe deck boat. I have a 13.25 by 15 prop that was getting 28mph max at 4800 RPM. The prop would cavitate in tight corners unless I trimmed way down through the corner. I took it to a prop shop to see what they could do. They added a little to each blade and cupped or spooned the blades at the edges. Now I get less than 25mph and only 4400RPM. It is worse! I tried a 13.25 by 17 and this is no better. Any suggestions Please?? Thanks, BJ

 

[rndn]

Re: '93 Johnson 115 prop help

I have a '93 Johnson 115 on an aluminum 22ft Lowe deck boat. I have a 13.25 by 15 prop that was getting 28mph max at 4800 RPM. The prop would cavitate in tight corners unless I trimmed way down through the corner. I took it to a prop shop to see what they could do. They added a little to each blade and cupped or spooned the blades at the edges. Now I get less than 25mph and only 4400RPM. It is worse! I tried a 13.25 by 17 and this is no better. Any suggestions Please?? Thanks, BJ

Welcome to the forum!!
You should be going the other way as you need less pitch instead of more. You should try to prop your boat so the engine reaches close to 5500 rpm's at wide open throttle(WOT). The rulle of thumb is that for every 1" of pitch change the rpm's change by 200. So if you're getting 4800 with the 15 inch prop you should try something in the 12 inch range. A 22 foot deckboat is alot to ask a 115 outboard to push which is why you need to drop to such a little pitch. These are readily available right here at iboats.com marine store.
http://boatpropellers.iboats.com/Ev...r=1993&**********=580355974&*******=803750666