Can't get WOT RPM

[BRIANLODGE]

Here we go again; I have a johnson 9.9 on a 24' pontoon. I haven't been able to get above 4100 rpm. This weekend I did some tests; I have a 9.5 x 9 prop. I tried tilting the engine and no change in rpm. I put on a 9.9 x 7 prop no change of rpm then tried tilting the engine again no change. I put on the lowest pitch prop the marina had which was a 9 x 6 no change in rpm. I checked rpm at helm tach, I had a hand held tach dwell meter and also used one from work where you put a silver dot on the flywheel and shoot it with a laser. All tachs are within 100 rpm's of each other. The marina said there is nothing wrong with the motor and just live with the 4100 rpm. FYI- it's a small marina with 1 mechanic and 1 salesman. About 30 boats sitting there to be worked on. Anyone have any suggestions. The motor does seem to run fine just no WOT RPM. I'm looking for a high thrust prop. The marina said they don't exist for the 9.9. I found a johnson site that says they do, I just need to find a place to buy it.

 

[Goodoleboy]

Re: Can't get WOT RPM

It sounds as if this motor is starveing for fuel. Or possibly out of time, or both.<br /><br />Is carb butterfly perfectly horizontal, Look at it with engine setting dead and throttle lever wide open. Then with engine runing wide open in the water, cover off carb. Is it going past horizontal.<br /><br />droping down in prop pitch should change RPM. If all is well with engine.<br /><br />Good Luck!

 

[BRIANLODGE]

Re: Can't get WOT RPM

Should have posted that. I checked the throttle, it is wide open. Perfectly horizontal. That was one of the first things I did a month ago or so. I've had the feeling they have limited my motor somehow. But why??

 

[Goodoleboy]

Re: Can't get WOT RPM

What does your service manual say about rev. limiter, if its got one mabey its gone goofie, try a new one mabey. Or disconect it for awhile and see if motor gets to 5500 or so.<br /><br />Good luck!

 

[BRIANLODGE]

Re: Can't get WOT RPM

It does have a rev limiter and in neutral you can hear it break up around 3500-3800 rpm. but I can get 4100 rpm out of the motor now and it does not sound like it's breaking up. My manual does not tell me how to adjust or disconnect the rev limiter, as I have tried finding that info so I can try what you recomended. Anyone know how to disconnect the rev limiter????? I''m still leaning toward starving fuel, but it doesn't break up. Just purrs right along. Same with the timing. It runs so nice It could be timming but I have a hard time beliving it would run so good if out of time.