Evinrude maxes at 3800RPM

[mckee1787]

My craft usually tops out at ~30MPH. Two weeks ago while cruising at WOT, the RPM dropped and my top speed now is only 20MPH@3800RPM. I checked compression on all cylinders that were all around 95psi and I am getting spark in all cylinders. I have a 1987 e90tlcur.

Thanks

 

[tashasdaddy]

Re: Evinrude maxes at 3800RPM

start motor on muffs, individually, pull a spark plug wire, rpms should drop, and sound change, replace wire, should go back to normal. if there is no change, you be that cylinder is not getting fuel.

i would do a decarb afterward and see if you can get compression up.

Decarb, take a can of seafoam put 3/4 of it in the gas tank, with only 1 gallon of premixed gas. put the rest in a spray bottle. start the engine, and let it come up to temperature. then remove plugs, and them some real good shot of seafoam into the cylinders, replace plugs, let sit 15 minutes. restart, and spray the rest of the seafoam into the carbs, so the the motor almost stalls, wait and repeat until the seafoam is gone.then take for a wide open spin. then put in new plugs, ad premixed gas to the tank, and take it for a wide open throttle spin. it is going to smoke like a house on fire, during this process.

afterwards compression.recheck

 

[kenmyfam]

Re: Evinrude maxes at 3800RPM

Spark could possibly be breaking down at higher RPM due to increased load. What was the spark plug condition like on each cylinder ??

 

[mckee1787]

Re: Evinrude maxes at 3800RPM

I did pull off the plug wires one at a time and did notice the change with each
one pulled.

kenmyfam, what would cause the spark to break down at higher RPM when loaded?

Thanks

 

[kenmyfam]

Re: Evinrude maxes at 3800RPM

I did pull off the plug wires one at a time and did notice the change with each
one pulled.

kenmyfam, what would cause the spark to break down at higher RPM when loaded?

Thanks

You are working your motor harder when asking it to push everything forward faster. Is there any change in hole shot ??
Have you done a spark test ?? Should jump a decent size gap with a nice fat spark. Just going back to my 2 stroke motorcycle days.