compression numbers

[merc20076]

I have tested the compression on those 2 outboards:

-1977 6 HP Evinrude:

85 PSI on both cylinders

-1983 7.5 HP Johnson:

85-90 PSI on both cylinders

Also the head is a different white than the rest of the powerhead, the motor doesn't overheat, I can keep my fingers much more than 3 seconds on the head beside the spark plugs.


Are those good numbers or there getting tired? I think it's pretty good but I'm not sure. My '80 4.5 Johnson have 95-100. The tests were done when cold. I didn't do a de-carb job yet.

I have a 2nd 7,5 HP but it needs a head gasket, previous owner took the head off and the top of the pistons are full of carbon.

I bought these 3 outboards for 300$ and they all needed small repairs and my plans are to re-sell them for a good price if they are ok.

 

[1946Zephyr]

Re: compression numbers

Yea, I would say that those are good compression readings. If they're the same on both cylinders, then that is all the better. You want them to be within 10% of each other.

As far as the motor with the head removed, how do the cylinders look? That there may be a good runable motor too. Clean the piston crowns off and put the head on and see what you get.

BTW I like your Crestliner in your post.

 

[merc20076]

Re: compression numbers

Yea, I would say that those are good compression readings. If they're the same on both cylinders, then that is all the better. You want them to be within 10% of each other.

As far as the motor with the head removed, how do the cylinders look? That there may be a good runable motor too. Clean the piston crowns off and put the head on and see what you get.

BTW I like your Crestliner in your post.

Cylinder walls looks fine, no rust or big scratches. I knew already that if they are within 10% it's ok.

My old 40 horse on my Crestliner says 95-100 psi but I did not open all the throttle when I tested it after the season and my starter has to be rebuilt very soon, may change head gasket too but I got to get new seals for the LU. But it runs like new so it's worth it I think, I really like the electric shift.

 

[samo_ott]

Re: compression numbers

You're one of the few that likes the electric shift. That's good to hear. I just got a '62 Lark on an Arkansas Traveler and she runs like a top.

 

[1946Zephyr]

Re: compression numbers

You're one of the few that likes the electric shift. That's good to hear. I just got a '62 Lark on an Arkansas Traveler and she runs like a top.

Hey Steve, that's a beauty. I always liked the old 40's styling.

 

[1946Zephyr]

Re: compression numbers

Cylinder walls looks fine, no rust or big scratches. I knew already that if they are within 10% it's ok.

My old 40 horse on my Crestliner says 95-100 psi but I did not open all the throttle when I tested it after the season and my starter has to be rebuilt very soon, may change head gasket too but I got to get new seals for the LU. But it runs like new so it's worth it I think, I really like the electric shift.

ok