Cafe with 465 Mercruiser convert to closed cooling?
 

I´m looking at a 1991 Cafe that needs some work, but looked like a nice deal. The seller now sent pictures and the 465 Mercs are fresh water cooled. Most of its life the boat spent in a lake, and was only recently brought to the ocean. My questions are now:

1. Do the old iron cast engines need a closed cooling anyway?
2. When I look into old specs I find that Cigarette offered these engines only raw water cooled at that time. True?
3. How can I find out if saltwater use damaged something without disassembling the engines?
4. What would be the cost to convert to closed cooling system?

The seller claims the engines have only 200 hours, 190 of them in freshwater.

A newby says thanks in advance..

Only picture is bad quality, I´ll attach it anyway

They all came raw water cooled.
I think you could convert for under 2500 total. But if you watch the used market I've seen them used for a couple hundred bucks a motor.
I am not sure where typical weak spots are, but mine rotted out where he aluminum intake met the iron block. Exhaust risers and manifolds are also common areas of corrosion related failure.

With any boat boat like that I'd buy it knowing you'll have some unexpected issues.....

I didn´t know that and my first thought was to run away when I saw they are raw water cooled. So this one is still a candidate.

Or not convert at all and flush regularly?

Risers and manifold have been replaced already, at least something.

Very true!

I debated it a long time, but when I redid my motors I just went back to raw water cooling. I flush every time I use it with saltaway. I have a valve to cutoff the raw water intake so I can flush when we stay overnight at marinas, etc. I sleep pretty well......

Sounds good, I guess I will do the same.

I´m just concerned that the current owner never flushed and left the boat in the water for a long time - judging from the hull color below the waterline.

Closed circuit has its downfalls too. My 496 Mag sucked up silt in a cove and plugged the heat exchanger so it would over heat and hit the guardian mode in 2 mins which made for a long slow ride to the dock.

Also coolant can cause electrolysis corrosion as well.

I know you can't cover every possibility and the $$$ keep adding up but would a sea strainer have prevented the issue sucking up the silt?

RR

Doubt it as most are design to stop large particles