Converting cooling system for Salt Water?

[Bigjim]

I was chatting with a member of my Yacht Club the other day and he told me something that totally shocked me.

I have a Yanmar 2QM20 with a raw water cooling system. I told him my longterm goal is to take my boat out to the ocean and sail over to Europe and the Med. When I told him what kind of motor I had, he said that I should not take it to the ocean as is.

He said that he would not use a raw water cooling system because it would get clogged up with sea life. He recommended that I convert the engine to a heat exchanger cooling system with glycol.

Is this true? Do ocean boats all have closed systems with heat exchangers? I have never heard this before. And, wouldn't the closed system get clogged with sea life too?

[Bigjim]

For that matter, the Great Lakes are rife with Zebra mussels, wouldn't they pose the same problem with my current system as any salt water organisms would?

[nightowle]

Most modern engines have a closed system for engine cooling. I can't comment on whether yours is suitable for blue water cruising. If it's worked fine to date and you just monitor the effects of salt, I think it should be fine. Whatever keeps the engine cool, is good.

[Bigjim]

Originally Posted by nightowle

Most modern engines have a closed system for engine cooling. I can't comment on whether yours is suitable for blue water cruising. If it's worked fine to date and you just monitor the effects of salt, I think it should be fine. Whatever keeps the engine cool, is good.

Sorry, may not have mentioned that my boat has always been in Lake Michigan, but was built in the 70s for ocean cruising...

[ItDepends]

Engines with raw water cooling have issues with salt water that do not appear in fresh water. But the idea that they are totally unsuitable for ocean use is silly. Boats with raw water cooled engines have crossed many oceans.

Just to make sure you understand the quality of advice you were getting at the yacht club bar, a salt water cooled engine does not clog with "sea life." It CAN clog with precipitated salts. This is minimized by careful control of the engine temperatures. It is why most saltwater cooled diesels have 165F thermostats instead of 180F ones.

[rslifkin]

If it's reasonable to convert, I'd say do it. Closed cooling lets you run a warmer thermostat (makes the engine more efficient and less prone to carboning up under light loads). And it's easier to keep the cooling system clean and healthy (plus no corrosion issues in the engine block). Other than a little added complexity, I can't think of a single downside to closed cooling.

[PJS]

Can't be certain on the logic of a raw water cooling system not being suitable for ocean cruising.

I am in salt water 100% in the Puget Sound. My engines are Mercruiser Horizon big blocks. The block is cooled by a closed system heat exchanger and the exhaust manifolds and risers are raw water cooled.

Yes, salt water does take a toll on the pump, manifolds and risers. Expected life is about 5 years. However, I combat that with flushing the raw water system if the boat is going to sit for a week or more. This flushes out the salts and keeps fresh treated (Salt-Away) water in the system. Every raw water intake should have a sea strainer to catch any debris. Sea life build up has NEVER been an issue for me, granted my boat does not sit unused for more than 4 to 6 weeks - even in winter.

Someone made a good point on cooling temps. My motors run at 168 degrees and I do have an issue with carbon build up when running at low idle for extended periods (plugs can foul). I typically run the engines at 3500 to burn out the crap...

I should think you would have no major issues with raw water cooling if you are not sitting in one anchorage for months at a time.

Why spend the money to convert? I don't see the practical gain in doing so.

[Rumrace]

Heat exchangers or engine blocks pumps can all get clogged. You can use too much antifreeze. Heat exchangers get ignored until it’s a disaster.
I think there are worse things then salt water cooling.
Follow the Yanmar instructions on adding the exchanger. Read the part where Yanmar states don’t paint the drive with a copper or zinc based paint cause you’ll eat the drive. Yanmar has the real answers. Some advise leads to disaster.

[Scorpius]

I have keel coolers for engine cooling. Works very, very well. Engine is freshwater cooled. No saltwater comes into the boat for engine cooling. No saltwater pump, heat exchanger, etc. The exhaust is dry. The high-quality automotive (small truck) muffler has lasted over 20 years.

[RaymondR]

Ran a 3GM30 with raw water cooling for 25+ years about half in half between the tropics and temperate zones and did not experience clogging once.

Unless you are converting to keel cooling a fresh water system needs raw water to cool anyway.

The main reason that marine engines are predominately bi system is that the modern engines available for marine conversion have exposed alloy components in the cooling path through the engine and if raw water cooled these components would rapidly corrode away. Which is why you should always use the recommended coolant and not just water.

[bil56]

a seawater-cooled engine has lower efficiency (too low temperature),
and engine metals in constant contact with seawater corrode more,
but no problem even to cross the ocean!
a seawater filter will protect your engine from algae and slightly large particles ...

[Pete7]

Originally Posted by Bigjim

I was chatting with a member of my Yacht Club the other day and he told me something that totally shocked me.

Lots of experts in yacht clubs, mostly in the bar

This is my raw water cooled Volvo 2003. Its 33 years old and has always been used in salt water. Sure, its getting on a bit, had a cylinder head job 10 years ago and last winter I gave the cooling system a good flush with acid for an hour to clean the cooling passages as preventative maintenance rather than anything that had to be done.

You will need to think about any anodes in the engine to ensure they are suitable for salt water. Also if you lay it up for a period, worth flushing through with anti freeze using the engine water intake and a bucket in the cabin. Don't put a hose on the engine directly.

Good luck with the trip across to Europe