89' 150hp, 2100 rpm max?

[will941s]

My 89' Yamaha 150 used to max out in the mid 5,000 RPM range, then last summer it would hit max RPM's then drop to 4'500 RPM's after it hit full WOT. I changed all the fuel lines and rebuilt the fuel pumps a few days ago and took it out to try it. This time it started and ran stronger than ever, hit full RPM's in a snap with the warm up lever and never skipped a beat. I put it in forward and poured the gas to it and.....2,100 max RPM's. I let off the gas and tried it again and it hit 2,800 and after a hour of trying the max it hit was between 2,100 and 2,800 RPM's. Sometimes it sounded as if it was trying to get up and go but it would just drop back and bounce between 21 and 2,800. I did'nt do anything to the carbs this time around and I was wondering if anyone has any advice on what I can do to fix this problem.

 

[cousinabe]

Re: 89' 150hp, 2100 rpm max?

you most likely have trash in your carbs. Have you cleaned out you main jets?
Another thought, I have read about the older fuel connectors causing restriction problems. The o-ring inside of it swells due to E10 fuels and causes a flow restriction. You can try plumbing your fuel line directly to the engine mounted filter.

Does pumping the primer ball help?

 

[will941s]

Re: 89' 150hp, 2100 rpm max?

When the RPM's dropping from the mid 5's to the mid 4's was the problem, pumping the ball would bring it back to full RPM. This time priming the ball did did nothing to bring the RPM's over 2,800. When I changed out the fuel pumps the top pump diaphram was torn and non servicable. I don't know if changing out the pumps knocked it out of sync or something being as it actually ran decent with only one pump, like it has been adjusted to compensate for the shortcoming of a bad pump. I did put a new style connector on the engine and used better quality hose. I also used a high capacity primer ball this time and a 10 micron inline filter.

 

[cousinabe]

Re: 89' 150hp, 2100 rpm max?

Clean your carbs and perform a link and synch.