crankcase pressure '67 evinrude 6hp

[oldcatamount]

1967 6hp Evinrude
Would a leaking upper crankcase seal cause this motor to quit running after about 5 minutes at WOT? It starts hard after it quits and will run fine for 5 to 10 minutes and then quit again. The gas tank vent is open, I have a new fuel pump, fresh gas/oil, new points, plugs, condensers, coils, wires, good compression, a clear gas line from the fuel pump to the carb so I can see the gas going through. It seems to run better without the cowl so I was wondering if the crankcase gases could be choking out the motor when the cowl is on?

 

[jacksoldoutboards]

Re: crankcase pressure '67 evinrude 6hp

I doubt it if it was working good before.. if the float level is too low - they will not run at WOT very long..? hummm!

 

[raczekp1]

Re: crankcase pressure '67 evinrude 6hp

hi.i had the same problem.hard start after warm up, but in my sytuation problem was old coils and condensers.
in my opinion low compresion will cause that is low vacum and you will not even start motor.
in my 73y compresion was aroun 90 psi per cylinder

 

[oldcatamount]

Re: crankcase pressure '67 evinrude 6hp

My boat is 16ft. long and I store the gas tank in the bow (under a cover that I built) so, it's a long pull for the gas to the motor but I tested the motor with a different gas tank that I put under the motor next to the transom. The "test tank" is an old metal one that I'm wondering now if it's venting right.
Glad to hear that it's probably not the upper crankcase seal because I wouldn't know how to change that anyway.