1990 Evinrude 48SPL sudden power loss

[dog5233]

I am experiencing intermittant powerloss on my 48SPL. Sometimes it runs no problem, at other times, at any speed, it will begin to hiccup severely. Usually if I bring it back down to idle, put it in neutral, and gently rev it, the problem will disappear....for awhile. It may reappear suddenly again in 30 seconds, or may go an hour or two of normal operation at the full range of throttle settings, and then happen again.
Carbs were very dirty and rebuilt by shop this spring to correct low idle problem. Shop advised at that time that engine had strong spark and compression equal on both cylinders and per new specs. They also replaced a defective thermostat. This problem happened once prior to carb rebuild early in the season so I though it was carb related. Engine starts/idles/runs very very well since carb rebuild, except until the hiccup problem recurred.

Plugs and wires replaced this winter. New Moeller gas tank, new fuel (although I know that doesn't mean it can't have water in it). Problem duplicated with two different fuel line/primer bulb assemblies. I do not have a filter water separator, this is on my short list for to-do's.

Any thoughts? I'm wondering about loss of fuel line vacuum at connector fittings, depending on how they are jostled around.

 

[tashasdaddy]

Re: 1990 Evinrude 48SPL sudden power loss

vent open on fuel tank?

 

[dog5233]

Re: 1990 Evinrude 48SPL sudden power loss

Thanks for the response tashasdaddy.
Yeah, tank vent is open. But, you raise a good point. On my two new 6 gal Moeller tanks, the vent in the filler cap is really a flimsy affair. When you close it, it's a fine line between closed and overtight - very easy to tighten it until it agin becomes loose, like you are stripping the threads. Similarly, it's a fine line between open and practically falling off. Maybe I need to make sure it is really open enough. Just cracking the vent on a cool partially filled tank is enough to equalize pressure, but maybe there's still to much restriction for the fuel pump to overcome if it's not open enough. Shooting in the dark here...

 

[tashasdaddy]

Re: 1990 Evinrude 48SPL sudden power loss

if the carbs were that gummed up, the fuel lines could have been also, and stuff is not breaking loose, fouling the carbs.

 

[dog5233]

Re: 1990 Evinrude 48SPL sudden power loss

hmmm.

Service records from previous owner indicated no carb mork over last 6 years, I just think they were ignored. Winterization and other items were done religiously.

I have two fuel hose/bulb assemblies. One is aftermarket and new this year, the other is OEM - I'm not sure but it does not appear externally to be very old either. First time this happened was with the new hose, dirty carb. And since has occurred with both hoses at least once or twice.
I have drained both hoses and have used them to siphon from one nearly empty tank to another at the end of the day, have not noticed an debris or particulates of any kind in the fuel.

When I install a separator, should I just have the quick disconnect fittings at the engine and tank like now, and make all other connections permanent with barbed/clamped connections? This would keep the fuel lines and bulb aboard always - currently I remove the tanks and fuel line when not in use and store in a cool shed. Adding more quick disconnects would allow line removal but would also introduce more potential leakage paths I would think.