1976 Evinrude 70HP Hesitates after warmup

[Greycup180]

--------------------------------------------------------------------------------

After running around the lake, we will go in to hook up a tube or skier (either shut down or idle) and then when we full throttle, the motor wiil hesitate and when I pull back and try throttling up again it will stall. Starts right up, but after full throttle will hesitate and stall. If I work the throttle back and forth I can eventually get it going but I have to unhooke the tube or ski rope then come back in and quickly hook up again to keep it going. Only seems to hesitate and stall after a short rest from a WOT ride. Tune up last year but I cannot remember the last time the carbs were thoroughly cleaned.

Thanks in advance.

 

[Joe Reeves]

Re: 1976 Evinrude 70HP Hesitates after warmup

With the engine NOT RUNNING but in forward gear, have someone slowly apply throttle while you watch the timer base under the flywheel.

The timer base should move smoothly from its idle position clear up to it full spark advance position. If it sticks anywhere = retarded spark = no power and the engine will die out.

If this is as it should be, either the carburetors are fouled or the carburetor throttle roller is not aligned with the cam scribe mark......... The throttle butterflies should just start to open when that scribe mark is aligned with the center of the roller.

If the engine runs fine at times, just not always, it's unlikely that the carburetors or the roller alignment would be at fault as they do not come and go.

 

[Greycup180]

Re: 1976 Evinrude 70HP Hesitates after warmup

Thanks Joe! I will certainly try the test for the timer base. I really don't think the carbs are at fault since the engine runs fine at the outset....hesitation only happens after a good warm-up and when we idle to hook-up a skier, or shut down for a couple of minutes. Could faulty points also cause my hesitation and choking out? My initial reaction to the hesitation and choking is that too much air is getting in or not enough fuel is reaching the motor. Maybe a air lock is occuring somewhere after a good warm-up??

 

[Greycup180]

Re: 1976 Evinrude 70HP Hesitates after warmup

Bump

 

[Greycup180]

Re: 1976 Evinrude 70HP Hesitates after warmup

Still having the same problem. After a warm-up, the engine chokes out when applying some throttle, but eventually it will kick in and we are up and running! Very annoying when trying to get a skier up as they will be towed around the lake until the throttle kicks in! Help!!

 

[jtexas]

Re: 1976 Evinrude 70HP Hesitates after warmup

No points in that motor.
Consider whether your carb float valves are worn, leaking a little fuel into the cylinders, flooding you out a little bit. Tilt the engine all the way up, see if any gas drips from the carb throats. (engine not running)
Or misadjusted, starving one cylinder under a heavy load.
What do the spark plugs look like, after the engine's been running?

Checked your compression lately?