115 "Topping Out"

[tryingtofish]

My 2000 2 stroke 115 will not exceed 2800-3000 rpm. If I can get it up on plane it will turn 3600 rpm. In neutral it runs up through all ranges of revs with no problem. Initially it was intermitant, would do it one trip, then didn't have the problem with the tech or me for a couple trips, now consistent for last month or so. The plugs were replaced during normal service in May and I've replaced the seperator and inline fuel filter under the cowling - both looked pristine and fuel was clean. I ran on portable fuel tank to eliminate fuel issues. The throttle is opening up with no binding in the linkage, so no problem there.
I'm running out of easy fixes and stumped as to where this might be coming from. Could it be a fuel pump issue?

[Tucker]

Can't tell if you're FI or carbed. Since it got progressivly worse; it sure sounds like fuel delivery. You got something clogged up.

[tryingtofish]

Its carbed. I'm thinking a clog too, just not sure where it could be. I 've eliminated the possibilty of anything between the motor and fuel tank. Guess it could be fuel pump or in the carb itself.

[tryingtofish]

Should I be to worried about pulling the fuel pump apart. Is there anything anythere that doesn't go back together intuitively? I hate to go tearing everyting apart and end up not knowing what I'm doing, but also feel like this is going to be one of those "duh" things when I figure it out.

[Tucker]

Not sure about the 4-cyl's, but my 6-cyl's have 2-low pressure fuel pumps. Keeping all hose connections in place, you can remove them from the block and pump the hand primer to see if the diaphrams are leaking. If they're 3-years old they should be replaced anyway. If they're leaking they usually dump fuel in the exhaust and you'll see an oil sheen at the dock when idling.

[tryingtofish]

OK makes sense, as far as I know i only have one fuel pump, the diaphrams are probably original. One question though, where would i detect the leak? I'll look tonight and post back results. I don't recall a sheen when idling, but never really paid much attention.

[Tucker]

The LP pump is driven by engine crankcase pressure. When you remove the fuel pump and pump the primer bulb till it gets hare you are putting pressure on the pump diaphram. If it's cracked you'll see it leaking through the little hole on the back of the pump. Carefull not to mess up the gasket when removing the pump. Also, when buying a new pump you have to order the gasket separately, it's not included with the pump. Pump and gasket should be around $40. Get on the boats.net home page and find your motor in the parts listing. My money's still on the carbs being clogged.

[jb123]

yep, sounds like carbs but you should also replace lp pump and gasket if it hasnt been recently
have you confirmed spark on all ?