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DBCochrane · 10-05-2012, 06:06

I am looking at purchasing a Najad 380. It has a 54 HP Yanmar (4JH3 HTBE) installed in 2005. It is a fresh water cooled engine. The engine only has 460 running hours. The boat is located in New England. The owner hauled the boat in autumn 2010, placing her for sale, and did not winterize the engine until autumn 2011. My question: What damage may have occurred due to freezing seawater in the system?

To partially answer my own question...I understand that raw water is drawn into a heat exchanger via an engine driven impeller pump. And the raw water in the heat exchanger serves to cool the fresh water/antifreeze mixture within the engine. So, following it logically, it seems that the impeller pump and heat exchanger may have damage.

nial · 10-05-2012, 06:18

As you say, the impeller and heat exchanger may be damaged but far worse and just as likely is a cracked head or block. If the cooling passages around those two items were left full of water and froze hard over the Winter then that engine may be junk. Only way to find out is to run it and see what happens.

**Don L** · 10-05-2012, 06:20

Did he drain the water initally? Start it up and run it as a good chance nothing is wrongif the though valves were open!

**jeremiason** · 10-05-2012, 06:22

Your best bet is to find a good mechanic who will survey the engine... In California, it cost about $500, but it is well worth it.

**Dockhead** · 10-05-2012, 06:35

Quote:

Originally Posted by nial

As you say, the impeller and heat exchanger may be damaged but far worse and just as likely is a cracked head or block. If the cooling passages around those two items were left full of water and froze hard over the Winter then that engine may be junk. Only way to find out is to run it and see what happens.

It's a fresh water cooled engine, so it is not likely that there is any raw water in the head or block.

You'll usually find raw water in the heat exchanger and perhaps in the exhaust manifold, which is where the risk of damage is highest.

**Pblais** · 10-05-2012, 06:53

Being lucky still counts.

I think you now have a list of possible out comes. Starting the engine and checking collant levels and the oil before and after should settle the big picture. You could still have other engine problems from before it was hauled out. So anything really is possible. It would also include a sea trial to really run the engine under load too. You'll be able to check engine cooling ability and oil pressure. I think a usual survey will find the worst possible problems quickly.

**ShaunJ** · 10-05-2012, 06:55

2010 was a cold winter, I winterized a little late that year with about the same Yanmar and was lucky to have only replace the raw water pump.

bobconnie · 10-05-2012, 07:15

Your telling me it was cold enough to freeze salt water ?? and don't most of ya drain the raw water system when ya pull the boat out ?? Ive found over the years that anti- freeze in the fresh water takes care of that ! Ive always drained the raw water system down and cked the anti-freeze amount and added if nessary, aways was enough for alaska! Just my 2 cents Ck the inpellers and change the oil and run it to see what ya got !!

**Hud3** · 10-05-2012, 07:33

If he didn't winterize the engine, what about the boat's domestic fresh water system? Be sure to check it for damage and leaks.

**zeehag** · 10-05-2012, 07:41

usually when i purchase a boat new to me i have the dealer /distributor/workshop of the engine within that boat do a 600 hour overhaul. makes engine like new and is a good idea. saves heartache later.

djmarchand · 10-05-2012, 08:22

I believe that the exhaust manifold is cooled with jacket water on that engine so the antifreeze should have protected the head, the block and the manifold.

Seawater freezes at 28 deg F, so it surely got a lot colder than that in New England.

As others have said check the seawater pump and the heat exchanger for leaks. It is possible that freezing of the seawater side of the heat exchanger damaged the tubes and they now leak into the freshwater side.

I would do a "radiator" leak test to find out if that happened. You can buy a kit for $20-30 bucks at the auto parts store and do it yourself.

The raw water heat exchanger and the raw water pump are the only two components possibly damaged.

David

David