1960 40 hp Evinrude surges at high speed

[rernst]

Old engine, hadn't run in ages. I cleaned out the fuel pump bowl. Then the carb as best I could without a kit, and got the engine started and it seemed to run pretty well in a barrel with water.

Took it out on the bay today, and whenever I opened up the throttle, it would go fast, then in about 10 seconds, it would REALLY lag, and almost die, then go with power again. If I choked it when it was dying, it was no help, so I'm guessing it's flooding, but not sure why throttling down let's it just keep running.

If I throttle down to idle or just above, it keeps running fine.

I've tweaked the high and low speed jets, but haven't been able to cure this.

I'm assuming it's fuel, vs. spark/coils/ignition, since it will run at full power for a short time, and will do it again within seconds of slowing down.

I plan to find/get a carb kit for it (but the float and needle valve looked great, no indentation in needle valve tip, and tip was still soft), and clean it out thoroughly, but wanted to see if anyone had any other suggestions on curing or diagnosing the surging problem.

 

[tashasdaddy]

Re: 1960 40 hp Evinrude surges at high speed

are you using new fuel? have you look at the coils? (inspection plate). through carb soaking and cleaning, rebuild kit. possible fuel pump failing. did you follow Joe Reeves directions in the faq forum on setting the carbs? have you check spark and compression???

 

[wavrider]

Re: 1960 40 hp Evinrude surges at high speed

After checking all the above mentioned items, next time you have it out on the bay and it slows down as you mentioned try pumping the primer bulb,
the fuel pump may be weak and not pumping enough gas to fulfill the requirements at higher speeds.
Also could be leak in fuel line, bad primer bulb any and all the above.

You mentioned engine sitting for a while, are you using new fuel line and primer bulb? If after market primer bulb been known to not work so good even if new, something about check valve faulty.

You are on the right track looking at fuel, once you get that straightened out post back to let us know what the results turn out to be.

 

[tmcalavy]

Re: 1960 40 hp Evinrude surges at high speed

Sounds like a fuel issue. A weak coil that fails under load/heat usually just fails with little recovery. I think wavrider's onto it...definitely pull/soak/clean the carb and then work your way back to the tank...lines, pump, lines, fitting, line, primer bulb, line, tank, etc. Also check the plug wires, could be worn to the point that one arcs/shorts at high speed.

 

[kenmyfam]

Re: 1960 40 hp Evinrude surges at high speed

Well it's a 2 stroke so it's either fuel or ignition !!!!
My thoughts are fuel from what you describe. Pump bulb if you are out again with the same issues.

 

[rernst]

Re: 1960 40 hp Evinrude surges at high speed

I haven't checked the coils, nor the compression. Plugs are good. Fuel is brand new, 24:1, tank to engine line and bulb aren't new, but from all I can see, they work fine (pumps fuel to engine, etc.) I don't think it's flooding after all, as neither choking, nor pumping the fuel line bulb helps at all. Choking seems to make it worse.

Since it runs really strong for a bit (varies, sometimes 30 seconds, sometimes less), and choking/enriching the system doesn't help, I don't think it's the fuel pump either. This has the rebuildable fuel pump type with the glass bowl. All I've done is clean the bowl and throw out the internal filter since I have a fuel filter in the gas line from the tank.

I haven't tried Joe's tips on adjusting the needle valves, but have been fiddling with them to get it to run and/or run faster. I'll try them again.

Need to find where oil is coming from lower unit, probably the prop seal, is my first guess. Time to look in my seloc manual to find out how to replace that.

 

[rernst]

Re: 1960 40 hp Evinrude surges at high speed

Oh, and any suggestions on best place(s) to buy a rebuild kit for my carb? Internet or local to San Diego?