Pontoon Outboard prop question.

[Grumman]

Hello new to the site. I have a 88 Grumman Funship 24'. with a 1973 Johnson 50hp. I put this motor on because the original FORCE blew a piston. I really like the old Johnson it has been reliable so far. my question is should I be able to go faster than 17mph on smooth water? The motor came off a little fishing boat so I think I may need a different prop. Currently has a 15 pitch on it and seems like it only gets to 2/3rds of top rpms, (don't know for sure, just going by ear no tach). it wont "spin out" the prop even loading on the trailer. What pitch should I try? or should I be happy with What I have? PropMD lists pitch's down to 10 I believe.

[killerkernrich]

I would say you are getting more top speed than most...I have a 22ft with a 2009 efi 4 stroke Mercury 60hp and 17-18 is what I can get no wind just me. I run a 10 & 11pitch. I may try a 9 pitch later on right now with the 10 my rpms are near 5000 book says wot should be near 6000

[Grumman]

Thank you for the comparison, I should add I have no factory seats Had to take them all out due to wood rot. just a deck and lawn chairs for now. So A little lighter than factory, on choppy water with wind and 4 people I would be around 13-14

[killerkernrich]

13-14 would be about right also

[RcgTexas]

Just to confirm your speed is not bad for the power on a 24 foot boat.

I have a digital tach on a big 35 hp Briggs on my mud boat . It attaches to a coil wire I think with a few wraps around it and gives good tachometer readings. wonder if that would work for you? You may have to have the engine cover off but then you could see whats up and prop the motor right.

[Grumman]

Thanks, Is your tach a universal one? where did you get it? I would be interested in getting one

[killerkernrich]

I got one of the very good ones called "Tiny Tac' off ebay around 45-50$ it tell rpms and hrs hours is what i needed very easy one wire you wrap around A spark plug wire the other to ground.