When to rebuild (or replace)

[jim.facey@gmail.com]

Hi, background, I've had the boat 15 years, had some sticky valve troubles for the first 4 four years until a friend did an in the boat valve job while I was on the hard. Since then the motor has run fine, I have learned a lot about keeping it going from this group here. My question is when to rebuild. The motor is now 46 years old and was last rebuilt in 1989, 30 years ago. I expect to have issues with manifold bots and possible even head bolts and for sure water jacket bolts next time I have to take anything apart. The guy who did my valve job will rebuild it cheap, if I get the motor out of the boat. I could also do a motor exchange for enw block with Moyer (this is appealing), but I have also begun to get interested in possible replacement with electric motor and maybe gas generator backup. Do I continue to wait hoping the motor keeps running (salt water coooled its whole life btw) fine as it does now for the 40 hours a year I use it? OR maybe plan on getting it out at the end of next season and doing oe of the three options above?

How long is too long without a rebuild?

[ndutton]

As for normal engine wear, it's my opinion that the engine will let you know. One telltale sign of progressive internal wear is blowby, that annoying smoke that comes out of the crankcase breather at the slash tube or in later stages, the oil fill cap and stinks up the cabin. Many owners add a PCV system to manage the smoke and stank but the existence of the smoke is an engine looking for attention. Another wear indicator is compression. It's easy to test, probably good to check it annually and record it in an engine log. With that you can identify a deteriorating condition if one exists and proceed with remedies when the time comes. A third indicator is falling oil pressure.

A lifetime of raw water cooling is a different beast. It is simply a matter of time until something rusts through and if that something is the block, it's a death sentence to the engine. Any rebuilding plans evaporate at that point. If you have budget available, the sooner you convert to FWC the better. It will arrest the rust instantly. Even if you replace the engine the FWC system is transferable.

As for the age of the engine, you report it has been 30 years since rebuilding. In comparison mine is 42 years old and as far as I can tell, has never been rebuilt yet still runs smooth and smoke free. The day will come I'm sure but at this time there is no indication it will be any time soon.

[Al Schober]

Neil puts it very well - the engine will let you know.
Aside from those issues, there's the stuff you want to do. Convert to glycol cooling, change the water jacket cover plate from bolts to studs/nuts, etc.
Many of us find working on an engine during the off season to be a pleasurable job - even therapeutic! Don't let the removal/reinstallation job scare you - quite easy with the mast in place.