Evinrude 70, fuel or electrical?

[MTBoat]

My 1983 Evinrude 70 shows these symptoms and I hope anyone with Evinrude experience might chime in to help me solve it.

Compression test numbers weren't great but within 10lbs each, top and bottom 10lbs lower than middle.

Starts up great.
Shift in gear under load/in water and it seems like when you start to throttle up it wants to bog down.
Ironically after a while of warm slow running it then began to gradually take throttle and we eventually got up to speed, BUT, still seemed like the unit was putting out about 25 horsepower and WOT produced 4200 RPM only.
Then, I took off the carb covers underway, slow, and when I put my hand over the intakes it was as if I gave it more horsepower??

Anyway we were finally kind of cruising, when we stopped and shut down, we had to go through a similar "warm up" period before it would take more throttle gradually.

Finally, we were cruising 28mph in a small 15.5ft fiberglass and all of a sudden the engine quit suddenly for 1 second, and then it ran another 20 seconds and suddenly just quit and no more starting at all. Done.

Is this indicative of fuel issue, or a bad fuel pump going south finally, or is it all more like some electrical weakening, then finally done?

Any input appreciated to figure if the motor is just plain tired and something else knocked in out finally, or its not getting what it needs one way or another......

Thanks

 

[oldcatamount]

Re: Evinrude 70, fuel or electrical?

It sure does sound like a fuel problem to me. A good place to start would be thoroughly cleaning the carbs, fuel filter, check fuel tank vent, and look for fuel leak around the pump and all fuel line connections.

 

[MTBoat]

Re: Evinrude 70, fuel or electrical?

I think all of the original problems truly point to a fuel issue and I should rebuild the carbs.

The sudden death issue seems to be electrical as I went out and could not produce a spark at the plugs.

Is there one or two typical areas that go that suddenly and drop all three cylinders?

 

[gm280]

Re: Evinrude 70, fuel or electrical?

I too think your first problem IS fuel delivery. When you placed your hand over the carb air inlet, you basically enrichened the fuel/air mixture and it took off. That tells me you do have a high speed jet circuit that is in need of a good cleaning and new carb kit or kits installed. And running lean like that did run the engine hotter then needs be. But Also check the fuel pump for a good output to the carb(s) too. I'd even replace all the fuel lines if they are a few years old. Fuel line is not expensive and can be a hidden problem as well... And finally clean out your fuel tank and check the primer bulb. Could be it has trash in it also. After doing all of that and you still have a weak running engine, then I'd look at the ignition...

 

[MTBoat]

Re: Evinrude 70, fuel or electrical?

Makes sense all the way around and will endeavor to follow through with some time and money.

However the apparent sudden lack of any spark to plugs makes me want to check/elimination process, the kill/stop aspect. I checked the rectifier and its ok. I wonder if running to lean/hot could have blown something, melted something?

But, I cannot seem to actually find the black/yellow wire to disengage. The Power Pack looks quite different from the ones in photos and I don't see that wire, or maybe it is hidden behind the pack and I need to take it off?.

Is there an easy place, or way to identify that wire to disengage it and see if I get spark then? I don't wish to buy a power pack on an assumption that it is the lack of spark culprit, when it may be a kill wire grounding out or that got melted/etc.