X dimension & prop ?

[dragstr19]

My nabor a new to him 20' pontoon with a 50 hp merc only two years old.The boat will only run 5mph at 3600 rpm seems kinda slow, but i really don't no about these. So any help with prop shaft height and prop size and pitch would be greatly appreciated. I know the boat isn't gona be very fast but it should at least run 10 or 15 mph shouldn't it. thanks for any and all help.

[rivermobster]

there is a plate on the motor somewhere just like this one. it will tell you the max RPM is should be running at. i think what you have there is a 3cyl merc.

change the prop pitch till you get it to run at the stated max rpm. thats about all you can do.

[Flying_Lavey]

Bury the prop and drop the pitch. Assuming that the engine is running fine. What prop is on there now?