I am sure that Mike just wants to enjoy his boat for a while before he has to pull out his wallet for a material set of investments. I know guys who nursed a bum engine for an entire year to save up the money to deal with it. As to the other engine.....it would seem that if the engines were replaced in 2015.....it may call into question the Previous Owner's assurances. I do believe it would be prudent to compression test both engines and take a look at the plugs. Old engine plugs are easy to identify since they usually foul quickly. In regards to Mike's question about where to find replacements......that is more complicated. The boat is 28 years old....so it will come down to what he finds when pulls that engine and how the other engine tests. Unfortunately...it never is just one thing when you re-power. The best case is no damage was done and the cause of oil pressure loss is repaired. Anything else will be far more expensive.