prop or height adjustment

[cuzzx]

i have a 20 ft pontoon with a 75hp mariner running a 13x19ss prop.

the toon runs good at 2000rpm, but tops out at 3000rpm.

as i give throttle forward the r's go up but the toon seams to bog.

i have tried this over and over with the motor in many different tilt positions.

i get the best for whats happening with the motor straight up.

the cavitation plate is about 2inches below the water line.

should i try to raise the motor or a smaller pitch prop.

checking with different prop selector sights they all say that a 13x19ss should work, thats why i'm thinking about raising the motor.

need help here on this, thanks

 

[Silvertip]

Re: prop or height adjustment

The reason you can't get over 3000 rpms is 1) the engine is not tuned properly or performing up to par but more likely 2) you have a very incorrect prop for a pontoon. I have a 19P prop on my walleye boat for example. You need to be in 14-15P range. With a 19P prop the engine is lugging something terrible -- sort of like trying to get away from a traffic light with a stick shift car in high gear. That will kill your engine. Get it propped correctly.

 

[cuzzx]

Re: prop or height adjustment

thanks for the reply, i have checked many prop sites and they all tell me
a 13 3/4 x15 alum. but what i can't figure is they also say a 13x19 in ss, which is what i'm running.