1975 70 hp Evinrude won't throttle all the way up

[Smith145]

I was heading back to the marina at full throttle when I hit a bit of wake causing the engine to slow down. I was very low on fuel and thought this might be the problem since the throttle would adust on it's own as the boat rocked. I filled up at the gas dock with 91 ethanol free, 50:1 2 stroke oil, and a capful of sta-bil 360. The problem persisted and basically was at half throttle when in WOT. Any ideas on how to fix this? I primed the bulb at the dock before I left but did not while running.

On a side note a small amount of oil/gas mixture leaks out of the shaft near the engine casing when pulling up the motor at the dock.

 

[1983 ercoa 21']

Have you pulled the hood and done any testing?
a common test would be a cylinder drop test by having the motor running pull plug wire one at a time to see if any difference the cylinder that does not change is the one not firing.
check the spark to see if it jumps a 7/16 gap
if that checks ok then do a compression test on all cylinders make sure they are all about the same.
if they are then move to the carbs by removing and disassembling and cleaning them very good.

 

[joecool911]

Maybe had one coil fail.

 

[F_R]

Don't dive into anything major before doing the simple stuff. Like check the spark plugs!!!

 

[Smith145]

Thanks for the help! Do I need earmuffs while doing a spark and compression test since I'll be cranking it?

 

[Smith145]

121/121/123 psi cylinder pressure. Spark plugs looked oily. Checked the fuel pump filter and the screens looked fine...