1981 evinrude no power

[Kevinthomsoncfc1]

Hey everyone. I have a 1981 evinrude 70 hp . It bogs out under power . I have no fuel making in to the middle cylinder. I cleaned the carbs and have new plugs in it . Verified good spark . Drove it with the air box off and can see all three carbs look to be fueling at the same rate . Yet I pull the middle spark plug and and the plug has never had fuel touch it . Reeds seem to be in good shape and sealed . I pulled the power head of thinking the lower crank seal could be gone as I could see a oil or grease build up in that area . Submerged the crank seal in oil and turned the engine over by hand . No signs of a air leak. I’m lost any new ideas would be great

 

[interalian]

Start with a compression test and report back. If you have spark at idle and see fuel being drawn into the suspect cylinder when running faster, I would then hang a timing light on that plug wire and see if it's firing under load. You can also do a "cylinder drop" test to see what affect pulling that plug wire makes. Compare that to pulling the wire from other cylinders. If you don't want to risk a shock, pull each wire individually with the engine off.

PS: welcome aboard!

 

[Kevinthomsoncfc1]

Hey sorry never added that I have 120 psi of compression across all 3 cylinders . When I pull the middle cylinder plug lead while driving there is no change to rpm . I have the power head on the bench right now. I wanted to check the lower crank seal. The seal appears to be ok. I do have oil build up around the lower area of what I think is the exhaust/ water manifold . Thanks for the reply

 

[interalian]

I think that's your answer then. If you have spark while cranking but not under load, you have an ignition problem on that hole. You can do the diagnostics on the CDI site, or swap the coils to see if the problem follows the coil. If it stays on the same hole, that puts the power pack or stator in question.

 

[Kevinthomsoncfc1]

I’m sure the spark plug is firing under power . When I take the plug out the head after a test run it is dry. It’s new plug . It has never had fuel touch it. I was thinking my full mixture was getting lost in the crank case . Cylinder 1 & 3 plugs have a nice brown colour on them . #2 plug is still just as clean as when I took it out the packet. Could I be loosing my fuel mixture through the exhaust manifold ? As I have oil around the gasket. I’ve tried to add photos but I can’t seem to get the file small enough to up load .

 

[interalian]

Timing light on the offending plug will prove one way or the other. If there's no fuel getting to that cylinder (plugged jet in carb for example), you will rapidly wear that piston/cylinder.

 

[Kevinthomsoncfc1]

For sure .i didn’t want to run it anymore . I cleaned the carbs and drove it with the air box off. I could see all 3 carbs fueling . Yet no fouled plug on #2 . That’s what’s making me think I’m loosing my fuel mixture in the crank case somewhere. The carb is fueling but the fuel is not making it to the cylinder

 

[Bosunsmate]

Put a dollar bill in front of the carb throat and see if shes sucking properly (as much as the others)

 

[racerone]

There are 3 separate crankcases.--------Each separated and sealed from the others.---So unlikely that the lower seal can do things to the #2 cylinder.

 

[oldboat1]

Any chance the middle plug is getting water-washed?

 

[interalian]

^^good question!

 

[Kevinthomsoncfc1]

I’ve ordered a re seal kit . Going to reseal the motor as I have it most of the way apart . And start trouble shooting her from the start again . Thanks for the ideas folks . I’ll let yous know how I get on once it back together.

 

[Kevinthomsoncfc1]

Oldboat1 when you say a plug getting water washed does that mean the cooling water would be getting into the cylinder and if so would that be caused by a head gasket failure?

 

[oldboat1]

Yes, and potentially yes. It would be wise maintenance to remove the head cover and resurface it, then reinstall with a fresh gasket. When you take a look at the old gasket, you might spot the problem if there is one.

To resurface, use 400 grit wet/dry sandpaper (or your choice of grit -- not too coarse) on a flat hard surface. Move the mating surface around in a figure eight pattern until the shine is uniform all around.

 

[Kevinthomsoncfc1]

Awesome thank you .