fluctuating horsepower.

[impalor419]

I am having trouble with my 1989 yamaha 130hp. Runs great with muffs. When there is a load on it it revs fine till i go. It lacks hp and at full throttle has slow speed and the rpms fluctuate up and down about 1500 to 2000 rpms. I have already changed the priming bulb. Fuel line from tank to rear. Rebuil the carbs. Can anyone help?

 

[99yam40]

Re: fluctuating horsepower.

Check compression on all cylinders , spark to all cylinders with spark tester, timing at idle and open throttle, fuel pressure and vacuum. Check you alarm system to make sure it still functions properly

not sure what this means "When there is a load on it it revs fine till i go"

 

[impalor419]

Re: fluctuating horsepower.

Check compression on all cylinders , spark to all cylinders with spark tester, timing at idle and open throttle, fuel pressure and vacuum. Check you alarm system to make sure it still functions properly

not sure what this means "When there is a load on it it revs fine till i go"

I meant... it revs up great until I shift in gear and start going. Running fine until at higher rpms. Full throttle is when it starts fluctuating rpms. From 4500 to 4100. Also no power. Should be going alot faster. How do i test fuel presdure?

 

[99yam40]

Re: fluctuating horsepower.

http://forums.iboats.com/showthread.php?t=283363


Timing light should also show if you are dropping spark on some cylinders by moving to different plug wires, but need to be looking when problem shows up. Testing peak voltages would be better if you have the equipment to do that.

Not sure if your motor has the low and high speed charge coils, but something to look into if no other problem is found