Ford Repair: ford 351 marine engine, ski nautique, 351 ford

Question
Hi
I am looking to buy a 1980 ski nautique that has a 351 ford marine motor (about 1200 hours).
Compression test as follows:
LHS     RHS
120     130
145     115
85**   120
125     120
Q1: how bad is this (**)?
Q2: if i do most of the labor myself what is it likely to cost in parts for an average rebuild?
Q3: what is the likelihood that this is a valve and not rings problem?

Any assistance would be greatly appreciated
Many Thanx
Brian Talbot, NY


Answer
I would suspect a valve or valve train problem. As far as cost, I cannot offer advise on that, my experience is in repair, not the sale or estimate side. Most shops will not offer estimates without checking things out themselves, most times. After a compression test the next would be a cylinder leakage test that will determine where the leak is.