1975 70Hp Evinrude Scored Cylinder

I recently pulled the powerhead off of newly acquired 70573B after discovering that my exhaust housing was bent (replaced the ext. exhaust hsg).

With the powerhead off, I figured that it would be a good time to check the exhaust/head gaskets & add a tell tale.

Exhaust manifold had alot of deposits and some corrosion. Cyl#2 had a water leak into the exhaust port (It may have some pitting on the baffle plate gasket surface...still cleaning gasket residue).

I pulled the cylinder head last night and found some light scoring in Cyl#1...along with dings in the piston & cylinder cover...it looks like something came-in through the intake and bounced over to the exhaust.






The score mark is very light...barely feel it with your fingernail and the engine has excellent compression...in fact, cyl#2 is a tad lower (139, 132, 138 on 1,2,3 respectively). Rings also look fine from the exhaust-side.

Leave good enough alone...watching for a performance/compression degrade???

If she had questionable compression, i'd already be ordering a new piston/rings and finding a marine machine shop...but strong compression has me puttin' the brakes on a total tear-down.

Thanks guys!

Re: 1975 70Hp Evinrude Scored Cylinder

There is almost exactly the same scoring on my '85 70hp and I have been running it that way for 15 years. No biggie. Mild exhaust side scoring is fairly common. Mind you, it is laying helpless on the bench so it would be a good time for such work...

Re: 1975 70Hp Evinrude Scored Cylinder

Leave it alone. Many people would kill to have those compression numbers on 10 year old motor let alone one that is 38 years old.

Re: 1975 70Hp Evinrude Scored Cylinder

TrueNorthist said:

There is almost exactly the same scoring on my '85 70hp and I have been running it that way for 15 years. No biggie. Mild exhaust side scoring is fairly common. Mind you, it is laying helpless on the bench so it would be a good time for such work...

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BonairII said:

Leave it alone. Many people would kill to have those compression numbers on 10 year old motor let alone one that is 38 years old.

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BII, TN, Thanks for the quick feedback!!! :tea:

In my Saturday morning rounds (Evinrude shop & hardware store), my trusty OMC guru was concerned about broken rings and advised to test by checking whether or not the rings spring-back when pushed from the exhaust ports.

I tested and all-six rings are "springy". :thumb:

Once I clean & dress the head (and add a tell tale), I'll put her back together as-is.

If it turns-out that I need to rebuild down the road, so be-it...not that much work getting these things apart again (only pain is to the wallet as these gaskets are a little spendy! )