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post #21 of 35 Old 03-13-2013
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Re: Raw Water Cooled for 35 Years?

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What really matters is the alloy used in the block, the chemical content and salinity of the raw water, and the durability of the engine.

Some have a reputation for enduring. Others not so much. I've heard that older Volvo engines in brackish to salt water will often rust through in the cooling passages, and that 25-30 years is all you can expect. I don't know if that's true or not.

But for any old raw water engine, used in salt water? You'd want to disconnect the water hoses, possibly pull the water pump or thermostat, whatever you have to do on that particular engine in order to access the cooling passages and see if they are eating into the block or not. Many are surprisingly robust.

And if the PO generally kept the raw water intake closed? Remember that raw water doesn't circulate unless it is OPEN, and whatever corrosion is going to happen, will self-limit itself if the water isn't flowing and being replaced. It very well could be fine.

Only way to really find out? Get some eyes in there, or a borescope.
I have looked at the inside passages of my 30 year old sea water cooled yanmar. What I see is white deposits and no rust or corrosion. I am thinking this is calcium carbonate precipation from the sea water.


I am hesitant to perform an acid flush of the system as all this coating may get stripped and actually increase corrosion rates. Maybe this coating is reducing corrosion of the engine block. Now if the calcium carbonate deposit gets too thick, then heat transfer will be reduced and the engine may start overheating.

I am thinking maybe do a 50/50 vinegar soak and flush once a year to keep the deposits to a minimal level, but keep them intack to protect against corrosion.
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post #22 of 35 Old 03-13-2013
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Re: Raw Water Cooled for 35 Years?

New engines can fail too!......Whether fresh or seawater cooled, the thing most likely to fail is not corrosion, but the rubber impeller. A good friend who lived aboard for 15 years told me to inspect the impeller once a year, and if it looks brand new, throw it away and put in one that IS brand new! When I bought Ragtime, my Perkins 4108 diesel overheated a little. The heat exchanger was nearly clogged with bits of rubber broken off "almost"good impellers! If properly maintained, a diesel will outlast a fiberglass hull, and they will last forever!
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post #23 of 35 Old 03-13-2013
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Re: Raw Water Cooled for 35 Years?

casey-
I'm not up on chemistry but yes, the white precipitation would be from salts in the salt water. And again, yes, it certainly could be sealing and protecting the bare metal underneath, so if it isn't creating a problem, letting it alone might be the best thing.

I understand that everything gets built to a price, but raw water engines....I just cringe that they are so popular. That's a mean thing to do to an engine, especially since those mineral buildups start at about 140F and engines simply are more efficient when running at 180-210F, which can't be done on raw salt water.

I guess no one really was thinking about "You know, this boat could last fifty years" when they spec'd raw water.
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post #24 of 35 Old 03-14-2013
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Re: Raw Water Cooled for 35 Years?

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casey-
I'm not up on chemistry but yes, the white precipitation would be from salts in the salt water. And again, yes, it certainly could be sealing and protecting the bare metal underneath, so if it isn't creating a problem, letting it alone might be the best thing.

I understand that everything gets built to a price, but raw water engines....I just cringe that they are so popular. That's a mean thing to do to an engine, especially since those mineral buildups start at about 140F and engines simply are more efficient when running at 180-210F, which can't be done on raw salt water.

I guess no one really was thinking about "You know, this boat could last fifty years" when they spec'd raw water.
I never liked the thought of raw water cooled either. And now days I think the only raw water cooled engine you can buy is a Yanmar 1gm (only 8 hp). But after owning a direct sea water cooled engine, I like it. Maybe like it better than a closed cooling system (although a keel cooler would be the best system I think). A well built sea water cooled engine is much simpler, and if you get a leak in the cooling system, no big deal, you have an ocean full of cooling fluid to use. Also the system is much simpler- one less fluid pump to maintain, no worries on antifreeze/boil over fluids to maintain, no heat exchanger to deal with, and all those fewer parts means the engine is easier to work on and get to.

I think the good direct sea water cooled engines were actually more expensive to make. That is why most engines today are closed cooling systems- they can take a regular tractor engine and throw it in a boat, where as a direct sea water engine had to be carefully engineered using correct materials and zinc to protect the engine.

An engine may work best at 180 deg F, but I would rather run at 140 deg F in a boat. The cooler running engine makes the engine compartment cooler- less risk of fire, and the engine likes sucking in the cooler air.

With both boat diesel engine types lasting a very long time if maintained, either type should provide adequate service.
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Re: Raw Water Cooled for 35 Years?

Beware of thinking simpler is better. That's how you wind up pulling the engine entirely.

The difference from 140F to 180F should not be a fire risk, even paper won't catch until 451F and that's a long way off. Heating the boat, yes, that's something else again. Poor insulation, poor ventilation, and no blower can all contribute to that. Even at 140F, you may want to run the blower after the engine is shut down, so it cools off the boat AND so it cools off the engine and prevents the oil from coking.

Or just pull the engine.

That was one of the problems in the VW Beetle, by the way. Air cooled engine, terribly inefficient. Simple, yes, reliable, maybe, but very inefficient.
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post #26 of 35 Old 03-14-2013
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Re: Raw Water Cooled for 35 Years?

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Beware of thinking simpler is better. That's how you wind up pulling the engine entirely.

The difference from 140F to 180F should not be a fire risk, even paper won't catch until 451F and that's a long way off. Heating the boat, yes, that's something else again. Poor insulation, poor ventilation, and no blower can all contribute to that. Even at 140F, you may want to run the blower after the engine is shut down, so it cools off the boat AND so it cools off the engine and prevents the oil from coking.

Or just pull the engine.

That was one of the problems in the VW Beetle, by the way. Air cooled engine, terribly inefficient. Simple, yes, reliable, maybe, but very inefficient.
I am not saying 180 F will cause a fire risk, but the hotter engine makes everything else in the engine compartment hotter. Things like the alternator, belts exhaust outlet, fuel in the fuel lines, elelectrical wiring and its insulation. The cooler these item run, the better for them and less risk of fire. I do not have a blower in my diesel engine compartment, and I do not think most diesels have a blower. I like being able to seal my boat up completely, should be able to take a roll over and only get some water in through from compainion way leakage.

Gasoline engines are required to have a blower, and due to lower ignition temp of gasoline, keeping engine and its compartment cool is even more important.

Air cooled engines are a whole nother ball game. Never liked them. Don't understand how one can maintain a constant engine temperature by blowing air. Never owned a volkswagon and even an air cooled porshe is just a glorified volkswagon- at least the air cooled models- on top of that, they sound like hell. My two cylinder lawn tractor sounds better than a 911. I always did like the look of the 911 Targa however.
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post #27 of 35 Old 03-18-2013
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Re: Raw Water Cooled for 35 Years?

36 yr old 2qm20h, raw water cooled, in a Bristol 29.9, 1500 hrs here.

keep the fuel clean and change the thermostat, impeller and zincs once a year and she will never skip a beat.

1977 Bristol 29.9
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post #28 of 35 Old 03-19-2013
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Re: Raw Water Cooled for 35 Years?

Get a motor specific survey. Compressions are a must, not just if the guy has the gauges. If the core is in good shape, clean her out and replace all wearables to get off to a clean maintenance start.

Hours on a motor are only an indication. Ironically, low hour motors that sit for extended periods can be worse than well maintained high hour engines that are run routinely. A good mechanic can sort it out.


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post #29 of 35 Old 03-21-2013
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Re: Raw Water Cooled for 35 Years?

Ran the original 1973 2QM15 raw water Yanmar until fall of 2012 in Far Cry. No hour meter so have no way of knowing how many hours were on it. Previous owner lived aboard for 15 years and had no solar so I know there were a lot battery charging hours. I had no issues with the motor other than parts were getting very hard to find and I assumed I was going to eventually need to replace something major. I ran across a financially distressed person with a rebuilt 2GM20 raw water cooled engine with transmission complete with all paperwork shrink wrapped on the pallet from the re-builder for $500. NO typo. Yes, I snatched that up and swapped motors. Ironically I spent far more than the $500 on new motor mounts, exhaust, hoses, coupling, fuel lines etc. in the process on installing it. Purrs like a top and the new owner is very pleased. A bad cell in a battery left me dead in the water just after I acquired Far Cry and I was able to use the decompression levers to hand crank it and get back into the marina. I love the KISS principle in the marine environment. I wouldn't hesitate to own another raw water cooled engine.
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Last edited by FarCry; 03-21-2013 at 05:59 PM.
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post #30 of 35 Old 03-21-2013
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Re: Raw Water Cooled for 35 Years?

Memo: Never arm wrestel with Far Cry! (G)

Seriously, though...whenever the subject of hand cranking comes up, grown men cry. How did you get the engine to turn over, even decompressed, well enough to fire it up?? Simple wrench on the crank, or cord on the flywheel, or... ?
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