70hp evinrude bog, but runs great at WOT

[rjcamel2355]

Hey guys, I have a 70hp evinrude, not sure of the model or year but it is a 3 carb 3 cylinder. Idles great, starts easy, but when you go to accelerate it sort of "stumbles" but runs absolutely great at WOT, new plugs, new fuel lines. If I tap the choke it kills it out.

Any tip of where to start looking? Will run a compression test on it today. Possible seafoam treatment fix? or a carb tear down?

 

[jakedaawg]

Depending on year, it may just be fine tuning the mixture.

 

[rjcamel2355]

120 120. 90. Compression. Bottom plug is clean. Cylinder spraying water out with the plug out and it running. Head gasket change time.

1976 by the way...

 

[flyingscott]

Give that cylinder with 90 a thorough looking over. You also want to change the exhaust gaskets on the side of the motor, that is a common place for water intrusion on those motors. More common than the head gasket failing.

 

[rjcamel2355]

Exhaust gaskets? Care to give me an idea where those are located? It's a straight 3 cylinder, the head gasket didn't look bad to me personally, and I've seen my share of failed head gaskets. I wasn't aware of the exhaust gasket issue, and now that you mention it. After pulling the head gasket and looking into the cylinder it looked like the exhaust ports had the water standing in them. The cylinder itself looks good, no scoring scuffing or anything like that.

 

[racerone]

??---Covers are on the side of the motor 3 gaskets in total.

 

[rjcamel2355]

I'll have to look at it when I get home this afternoon, see if I can locate it.

Do you happen to have a part number for the gaskets? So I can order them/see if I can find them?

I've got the head gasket number, even though it looked good I don't plan on reusing it.

 

[flyingscott]

If you are staring at the back of the motor on the left side is the exhaust housing. It is basically that whole side of the motor take that off.

 

[rjcamel2355]

Gotcha, I'm looking at the parts breakdown for that, It seems there are two gaskets to replace there? and sometimes a "warped exhaust plate?"

 

[flyingscott]

When you have the exhaust off look at that piston that is at 90 psi. With the plates off you will be able to see in side there through the exhaust port..

 

[rjcamel2355]

It is just three gaskets though? 331917 and 319097 and 0317228

 

[rjcamel2355]

Serial j0015285. Model. 70673d