have bf100 10hp on 14ft 36 johnboat . motor runs great, but seemed to run out of power right before boat planed out. does not matter if one person or two in boat. so installed tach. motor only turns 4140 -4200 rpms w.o.t. it has factory yellow prop, pitch not know, cant find on prop, or any information anywhere about the yellow prop. found owners manual online for bf100 and it said motor should perform around 5000-5500 rpms. what to do? rejet carb to see if can get more out of it, and if so witch is bigger by #size? or do i need to reprop? smaller pitch to get more rpm, or bigger to get more speed on top end to get boat on plane better. not looking for race performance out of a 9.9 hp fourstroke, just looking for the little more than getting out of it right now. any help would be great. thanks.

The only prop available, to my knowledge, is a 91/2 x 83/4. The original prop is no longer available. It is the only one used on all the BF75, BF100, Bf8A's.

Normally, I would suggest a lower pitch prop to get the rpms up.

I would not modify the carburator. I do not know what it will do, but I do know that it will lessen the life of the engine.

One thing you can try is a hydrofoil on the lower unit. It might help get the back end of the boat up and could help the planning.

I am also assuming that you have the motor tilt pin in the lowest setting. If not...move it there and it might do the trick. If it gets the boat on plane, then, if you moved the pin more than one hole, you could play with it to get a good balance of planning and speed.

The bigger prop would just bog you down more.

Mike