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Old 31-12-2018, 11:08   #1
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Heat exchanger in an old boat

I have a 1980 paceship that, until now, has only seen fresh water sailing. The current plan is to go east with her and sail the ICW and south soon. The boat currently doesnít have any heat exchanger on it. Adding one isnít cheap and I am wondering if it is even worthwhile when the engine is almost 40 years old already. If I donít bother adding one, how long can I expect the engine to survive? If I add one, any suggestions on who ch models are right for this small diesel? The engine is very clean and probably has less than 400 total time on it. Thanks!
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Old 31-12-2018, 12:56   #2
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Re: Heat exchanger in an old boat

What make & model engine is it? If it's designed for raw water cooling with anodes & a thermostat to suit it will be no problem. E.g. we have a 1980 Yanmar which has been used exclusively in salt water & the block is virtually like new as the anodes have been replaced regularly. Keeping the anodes up to spec is essential but if you do you may get another 40 years out of it.
The seawater cooled engines thermostat should be fully open about 55oC. You can test in a pot with a thermometer if the missus doesn't catch you.
Cant be any hotter as the salts start to precipitate out & clog the galleries. Hope that helps
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Old 31-12-2018, 14:03   #3
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Re: Heat exchanger in an old boat

It is a tiny SB8 diesel by Yanmar. The engine looks and runs like brand new. It does have a place for two anodes. I would assume they take a different material for saltwater. Interesting answer, I wil check out that thermostat while the other half is at work!
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Old 31-12-2018, 14:12   #4
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Re: Heat exchanger in an old boat

Not knowing the engine or setup hypothetically it would prob run you around $1000 - $1500 to convert if you do all the work yourself. Dual pulley, external water pump">raw water pump and a heat exchanger, expansion tank, some hose and clamps and new thermostat. It all depends on how much room you have, engine placement etc. You could also go to a keel cooler but that will be even more.
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Old 31-12-2018, 14:19   #5
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Re: Heat exchanger in an old boat

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Originally Posted by pacesetter View Post
It is a tiny SB8 diesel by Yanmar. The engine looks and runs like brand new. It does have a place for two anodes. I would assume they take a different material for saltwater. Interesting answer, I wil check out that thermostat while the other half is at work!
Ok,
I'm pretty sure the SB8 will be fine. Anodes are zinc for saltwater but THINK magnesium is the fresh water anode of choice. We make our own anodes as you just need a bit of zinc rod & an ss bolt & Yanmar parts are gold plated in NZ. Ours is a YSM8, very similar engine but horizontal cylinder. If it has that low hours I'd hang on to it as it is barely run in & they are very sturdy engines that are simple & easy to fix. Like the look of paceships but thats because they are very similar to our Compass 790 so I'm biased
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Old 31-12-2018, 14:20   #6
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Re: Heat exchanger in an old boat

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Originally Posted by pacesetter View Post
It is a tiny SB8 diesel by Yanmar. The engine looks and runs like brand new. It does have a place for two anodes. I would assume they take a different material for saltwater. Interesting answer, I wil check out that thermostat while the other half is at work!
I'm with Compass. Just stay on top of the anodes and go with it as is. And by stay on top of I mean check them once a month. As the salinity varies so will their lifespan. Also, the more you run your engine the faster they go just from simple erosion of water flow. You want to make sure you're changing them before they are gone.
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Old 31-12-2018, 15:11   #7
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Re: Heat exchanger in an old boat

If a trailer sailboat, or hauled out for off season, make sure you do a good fresh water run of engine before laying up. You don't want the salt water to evaporate in the engine and leave hard salt deposits behind. I have had a lot of raw water cooled engines that I ran in salt water, and with good maintenance no problems.

Note that good maintenance includes timely replacement of hoses, zincs, hose clamps (all SS), and water pump. Periodically check carefully for any water leaks and fix any immediately. Fresh water rinse, paint, grease and WD40 are your friends.
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Old 01-01-2019, 13:43   #8
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Re: Heat exchanger in an old boat

You will get a calcium build up in the cooling galleries. If you had a heat exchanger the calcium build up will be in that. If you start to have overheating problems then simply run an acid through the system. Watch a few "Barnacle buster" videos on Youtube to get some idea. Don't expect much more than another 40 years out of an engine though!
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Old 01-01-2019, 16:22   #9
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Re: Heat exchanger in an old boat

Switch out the thermostat to one that's less than 160 degrees. Above 160 degrees salt precipitates out of the water leaving hard deposits that will eventually restrict/block cooling passages. Other than that, the old Yanmars were mostly raw water cooled and lasted for years. If you are talking a year or two in salt water, not a problem. With the lower operating temperature, you won't have hot shower water with an engine coolant heated water heater, btdt.

Believe the sacrificial anodes are mostly in the freshwater cooling system with its dissimilar metals, copper cooling coils and the iron housing.
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Old 01-01-2019, 19:35   #10
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Re: Heat exchanger in an old boat

My 1982 Newport 28 had a 2-cylinder Universal diesel which was raw water cooled when I purchased it (and had never been in salt). I converted it to freshwater cooling with the factory kit. It was easy and relatively inexpensive. The boat made many saltwater passages while I owned it and is now owned by another sailor in my homeport area. That means the engine is now about 35 years old. It has had one top end rebuild and is still going strong.
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Old 01-01-2019, 22:59   #11
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Re: Heat exchanger in an old boat

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Switch out the thermostat to one that's less than 160 degrees. Above 160 degrees salt precipitates out of the water leaving hard deposits that will eventually restrict/block cooling passages. Other than that, the old Yanmars were mostly raw water cooled and lasted for years. If you are talking a year or two in salt water, not a problem. With the lower operating temperature, you won't have hot shower water with an engine coolant heated water heater, btdt.

Believe the sacrificial anodes are mostly in the freshwater cooling system with its dissimilar metals, copper cooling coils and the iron housing.
This is the correct answer.

Zinc annodes for salt water, but you need to drop your thermostats down below 160 to avoid salt deposits in the raw water galleys.

Otherwise you are good for several years.
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Old 01-01-2019, 23:53   #12
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Re: Heat exchanger in an old boat

I won't worry about changing thermostats - AFAIK, the SB8 uses the same thermostat as the other Yanmar raw water cooled engines of that vintage (YSE, YSB, YSM etc). They operate at about 55 to 60 C. There are two part numbers but they both operate at the same temperature and are interchangeable.
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Old 02-01-2019, 13:13   #13
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Re: Heat exchanger in an old boat

Hi, pacesetter,

We used to have a raw water cooled engine. You'll want zincs in there. If you develop overheating problems, we found acid washing the cooling system did a good job. [Fill large bucket with salt water and add swimming pool acid . Remove the zincs first (or the acid will eat them first, before the salt deposits). Run intake and exhaust lines to bucket, so you can re-circulate the solution.] It's rather amusing to hear the chemistry at work. You let it sit until the reaction stops, then re-install zincs, and go back to regular water circulation.

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Old 06-01-2019, 14:50   #14
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Re: Heat exchanger in an old boat

Thanks all! I feel much better and will go with it as is (except for new anodes). The low time of the engine makes me want to save it and pile a bunch of hours on it running around and having fun!
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Old 06-01-2019, 15:19   #15
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Re: Heat exchanger in an old boat

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Thanks all! I feel much better and will go with it as is (except for new anodes). The low time of the engine makes me want to save it and pile a bunch of hours on it running around and having fun!
Glad you posted what you were going to do. Don't know if listening to a single cylinder diesel could be classed as fun ( I find earplugs are a necessity in the cabin) but given that caveat the engine should be fine for thousands of hours if you feed it clean fuel,oil, do the recommended maintenance & change the anodes.
Did you check the thermostat?
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