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prop help

shavedhead

New member
I have bought a 18 ft. pontoon with 1999 merc.50 that runs great,it has alum. prop F10.13x15p, on the foot is a sticker that says 12x22 1.83:1,
At wot tach is showing 4200 rpm. and gps shows 17.3 mph. Sticker on engine says 5500 rpm, It is time for a new prop and looking for advice on what to use, Being a man I would like more speed,but I do not pull tubes or anything,used solely for cruising,I am looking to do what is best for my engine.Thanks for help.
 
Is tach accurate,thats alot of boat for that motor,a less pitched prop will give higher rpms and less carbon buildup in engine,and longer life on same,
 
as far as I can tell tach is accurate,there are 18 and 20 ft. pontoons everywhere here with 50 h.p motors, I was thinking of probably going with 11" pitch, but not sure.
Looking for input cause I certainly not expert, Thanks
 
ask other boaters what pitch& diameter there using with same hull&motor.according to theory 1 inch of decreased pitch will give approximately 100 rpms.
 
11" pitch sounds a good idea , depending on the load of the pontoon. Empty I would sggest 121/2" which should bring the motor better to live and increase speed.
13" diameter is also a lot for that motor!
 
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