RPM'S to low

[2ner]

I'm a new boater, I just bought a 2003 Crestline Pontoon w/ a Johnson 40 hp 4 stroke engine (fuel injected), it has a 11-1/2X13 prop. The first time I put it in the water it was toping out at 4000 rpm's at 6 mph's. When I flushed the engine out with the water hose I tested to see how many rpm's it would give me, with out being in the water and it revs way up. Can anyone tell if its normal for the engine to rev at 4000rpm's. I thought it should rev higher to use its full hp.

 

[rrhodes]

Re: RPM'S to low

WOT-RPM range: 4500-5500 but don't rev it out of the water. There is no load on the motor so it is not a good test anyway and it is bad for the motor to run High rpms on muffs.

What model and size is your toon?

 

[2ner]

Re: RPM'S to low

The pontoon is a 2003 Crestliner 1882 sport lx 18'

 

[Rancherlee]

Re: RPM'S to low

11.5x13 prop is way too much prop for that pontoon. Your Engine is the same as a Suzuki DF40 which has a 2.27 gear ratio and should be run around 5800rpm WOT. A 13 pitch prop is for a boat that will run in the 26-30mph range. I would drop down to a 9 pitch and give that a try, I think its the lowest one available and is made for pontoons and boats that run in the 15-20mph range WOT range.

 

[2ner]

Re: RPM'S to low

Thanks for the knowledge I will try it this weekend. Does it matter who make the prop? Does the diameter matter also?