Low compression on #5 on 1976 115hp Merc

[toycruiser]

I bought fiberglass boat with a 1976 1150 Merc. that has been sitting for quit some time. I did a compression test today and had #135psi on everything except #5 it had #35psi. I blew compressed air into the cylinder to see if I could hear excessive blow-by, and could not. I sprayed some penetrating oil into the cylinder and there was little change. Is there an inspection plate that I can look into that cylinder to check? Could it be a stuck ring? Is this thing worth repairing on one cylinder giving the age. I have more questions than answers as I am new to outboards, but I'm capable of doing most of my own work.
Any help out there?

 

[1nebel0]

Re: Low compression on #5 on 1976 115hp Merc

A stuck ring isn't going to give you that low of a number...you can buy motors all day long on Craigs List if you know what you are doing as many guys will lie about the condition of the motor or it's laying on the ground and it ran perfectly last time used..Yeah right...been there and done it before I learned what I now know....

 

[Chris1956]

Re: Low compression on #5 on 1976 115hp Merc

Toy, remove the lowest of the three transfer plates on the starboard side of the motor. They should come off w/o issue. You will be able to see cylinders 5 and 6.

It is unusual for #5 to go bad first, so maybe you will see a stuck ring or something simple.

 

[toycruiser]

Re: Low compression on #5 on 1976 115hp Merc

Toy, remove the lowest of the three transfer plates on the starboard side of the motor. They should come off w/o issue. You will be able to see cylinders 5 and 6.

It is unusual for #5 to go bad first, so maybe you will see a stuck ring or something simple.

Thanks Chris, I will pull the cover off this weekend. I can blow compressed air into the plug hole and roll the motor with it, so I would not think hole in piston. More afraid of salt water corrosion.