Evinrude motor troubles?

[B_Stone]

I have an 18hp Evinrude, the motor wont rap out all the time. It's like it has a mind of it's own. It only runs right once in awhile. I have changed everything. I used it over the weekend and burnt 12 gallons of gas threw it. It will only run half throttle and thats with the handle turned as far as it will go. Does anyone have any idea what is wrong with this motor or how to fix it?

 

[Joe Reeves]

Re: Evinrude motor troubles?

Bobby.... Regardless of the problem, always check the compression and ignition (spark).<br /><br />The compression should be approx 80 to 100psi on that engine (depends on the cranking rpm) and even on both cylinders.<br /><br />Spark, with the plugs out, should jump a 1/4" gap on both cyls with a strong blue flame. Check the spark at all throttle settings from dead slow to the fullest advance point.<br /><br />Let us know what you find on the above.