CONTINUOUSWAVE

Hello All. I am new to the site and actually new to boat ownership. I am buying a used boat that has a 1984 Mercury three-cylinder 115 that is losing compression. [The seller] says 70-percent in top two cylinders and 50-percent in bottom cylinder.

I am going to rebuild the motor myself. Am I being told accurate information?

One of the best things a mechanically inclined, new to them, engine owner can do is to obtain a shop Manual for the engine.

Assessment of outboard engine cylinder condition is usually done with a peak pressure test. For more advice on assessment of used outboard engines, please read an article on that topic in the REFERENCE section. See

Assessing Used Outboard Engines
http://continuouswave.com/whaler/refere ... Check.html

I advise you to not waste time and money buying a 33-year-old outboard engine that appears to need an immediate and substantial investment in time and money in order to be useful.

I don't know how to assess the accuracy of information you have found on the internet or been told by a seller of a used engine. Your question is not answerable.

This website focuses on Boston Whaler boats. The rebuilding of c.1984 Mercury outboard engines is not an area of discussion in which we have particular concentration, expertise, or focus. I would expect you could find better advice on the process of rebuilding a c.1984 Mercury outboard engine on another website whose focus is vintage or classic outboard engines.