Sportster won't rev above 5000RPM

[CaptSteve]

I have a 2001 Sportster LE with a single 947. The problem is that is will not rev above 5000RPM. Boat starts right up, idles smoothly, jumps out of the hole, no cavitation. The problem is that the engine revs from idle to 5000RPM at 3/4 throttle. From 3/4 throttle to full throttle, no change. Boat will run all day with no problems, but it will not rev above 5000RPM. It has been this way since I bought the boat last year.

Here is what I have done so far.

1. Had both carbs re-manufactured by National Carburetor in Jacksonville.
2. All fuel lines have been replaced.
3. Cleaned fuel selector switch. No obstructions.
4. Fuel is fresh
5. New fuel filter
6. Both Rave valves have been cleaned
7. New spark plugs. NGK BR8ES. Plugs are not carbonizing up and look good after running.
8. Battery is fully charged.
9. New water injector valve.
10. Charging system is putting out 13.5v @ 5000RPM.
11. Compression is 148/149.
12. New fuel baffle pickup.

I have no idea what to try next. A friend suggested that maybe I have a children's key which limits RPM, but I did not think that feature was available in 2001.

Is it possible that the MPEM rev limiter could have been programmed not to exceed 5000RPM rather then 7200RPM.

 

[El Toro 33809]

Would it rev to 7,200 before the carb rebuilt? Are the carbs opening to full throttle?

 

[CaptSteve]

Would it rev to 7,200 before the carb rebuilt? Are the carbs opening to full throttle?

No, that is why I had the carbs rebuilt. Yes, I checked and the butterfly's are fully open and equal at full throttle .

 

[Stevego]

What speed are you hitting at full throttle? Any chance the gauge is malfunctioning or not accurate? How about throttle cable adjustment is it snug at full throttle? Although you do mention carbs open fully at full throttle so assume it is ok....

 

[CaptSteve]

What speed are you hitting at full throttle? Any chance the gauge is malfunctioning or not accurate? How about throttle cable adjustment is it snug at full throttle? Although you do mention carbs open fully at full throttle so assume it is ok....

The top speed I can reach with just me in the boat is about 29mph. I would think I should be able to get close to 40-45mph.

I forgot to mention that I also installed a new throttle/oil pump cable.

 

[CaptSteve]

Found the problem. It seems there was a hole in the hose going to the pulse pump and it was sucking air. Also found that two of the gaskets in the carb where put on wrong. The gaskets did not cause the problem, but is shows you even the "Pros" who rebuild carbs can screw up.

 

[Seadoobuddy]

Good diagnosing.

Have you tested it on water yet?

A lot faster than 29 I bet.

 

[CaptSteve]

Finally had a chance to water test the boat. It runs great now and reaches 6800 RPM with no problem. Speed with just me in it is now around 42-44mph according to the speedometer in the boat.

I will get my GPS to find out what the speed really is.

 

[Stevego]

I have the same boat as you. Alone in the boat I have hit around 52 on the speedo. I also think it revs closer to 7000 rpm. Sounds like you are still not getting full throttle.