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Old 12-05-2008, 03:05   #1
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Fresh or raw water cooled??

I am looking at buying my first boat, and I am sure this topic has been bounced around many times before on this forum, however.. local advice I've been getting is that I MUST try and buy a boat with a diesel that is freshwater cooled. However, I must digress... going around the Marina, and talking to REAL SAILORS on REAL BOATS, I actually looked at a REAL Perkins diesel which has been raw watercooled all of its 16 years of life!

What gives? I realise that the modern freshwater cooled engines are also used to provide on board hot water. Digging deeper, once again talking to real sailors, they reckon because and the engine is not designed to run redhot, the best "hot water" they ever received is only moderate at best.

I would like to throw this open again, because due to my budget, most of the boats I am looking at are raw watercooled.. should I be afraid or not? A lot have had very recent rebuilds with low hours. Should I crucify them and walk away just because they are not freshwater cooled?

Any advice from the forum would be gratefully appreciated.

Cheers,
Donny
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Old 12-05-2008, 03:11   #2
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...
What gives? I realise that the modern freshwater cooled engines are also used to provide on board hot water. Digging deeper, once again talking to real sailors, they reckon because and the engine is not designed to run redhot, the best "hot water" they ever received is only moderate at best...
Running at about 180 deg. F, most freshwater cooled engines produce hot water that is dangerously hot.
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Old 12-05-2008, 03:24   #3
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The two Perkins I have onboard are fresh water cooled. The hotwater via the hotwater heat exchanger in my hotwater tank comes out at about 150 degrees F which is higher than what it is being heated by the electric elements (140) shore side. I would actually have preferred a fresh water cooled with a keel cooler like the previous boat I had but this one has the typical freshwater cooled with the raw water exchanger. I have never wanted a totally rawwater cooled engine. I reserve that method of cooling for outboards. Seen too many problems with corrosion.
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Old 12-05-2008, 03:32   #4
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Yep freshwater with a keel cooler. Hot water hating can be regulated using an adjustable car thermostat on the heat exchanger side of the heater.
. The thermostats on raw water engines are set lower because salt water becomes a lot more corrosive at higher temperatures. This in turn reduces the efficiency of the engine.
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Old 12-05-2008, 04:00   #5
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Thanks

I really should clarify somethingthe boats I'm looking at are small cruisers up to 33 feet. All these boats are equipped with single cylinder diesels. I have yet to see a single cylinder diesel with a heat exchanger.. (Volvo?)

I really need to get a handle on this, or I will be costing myself some serious dollars. As for "not so hot" hot water, is it possible for these heat exchanges to become clogged with salt or something?

The last fellow I spoke to warn me about "diesel bug bacteria" telling me he bought some fuel from a reputable outlet, only to have injectors block at the wrong time and place. Is this thing really a growing organism? Sometimes I think I should just go for an outboard motor on a vessel so small, but I've already experienced the horrendous cavitation on such an equipped vessel. But ease of maintenance and replacement are spectacular. Even without the efficient battery charging of an alternator.

I am finding myself drinking more and more alcohol to cope with these growing dilemmas! I will gladly take on board comments for either, I honestly did not think buying a boat be so difficult. (Easy I guess, if you are a "wood duck"...)

I will be so appreciative of comments from any direction.
Please bear in mind,this vessel will NEVERbe cruising far offshore.

Regards,
Donny
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Old 12-05-2008, 04:19   #6
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Raw water cooled is OK providing the engine was designed for raw water cooling in the first place. As you have noticed, it was (is?) the norm. in smaller engines/boats. I have owned 4 engines all raw water cooled (OK perhaps 3 - the 4th one hasn't being commissioned yet). 2 Yanmars, 1 Arona and 1 Buhk. Keep the annodes up to them and they last for years IMO. I suspect (but don't know) that heat exchangers give more grief.
BTW, I think an engine is more important for inshore work than offshore work and make sure you are drinking quality alcohol - life is too short to waste on cheap booze.
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Old 12-05-2008, 04:39   #7
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I really should clarify somethingthe boats I'm looking at are small cruisers up to 33 feet. All these boats are equipped with single cylinder diesels. I have yet to see a single cylinder diesel with a heat exchanger...
Most 27 - 36 Ft. cruisers, I've seen, will be equipped with 12 - 20 HP, 2-Cylinder diesels.
Most single-cylinder engines will be too small for these boats, under most circumstances.
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Old 12-05-2008, 05:07   #8
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As Gord has said with addition that you will be very hard pressed to find a new raw water cooled engine.
Further. at 36 feet 20 hp 2 cylinders will be adequate. But not comfortable. I am the last person to suggest that you over power. My little boat (30 foot) was originally designed with an out board. It was changed by passed owners to an in board single diesel. The prop comes out at the back of the keel, making it unlikely for it to break water.
Out boards ##One...even with a long leg it can lift out of the water.....two do you really want petrol on board?
Single cylinder diesels are not sold much these days (if at all)
There have been a plethora of raw water cooled diesels over the last 50 years. They have proven themselves to be reliable. Sadly that is no longer the point. They where built with a huge amount of material to make sure that they could sacrificially stay reliant. Not a bad thing.But fuel economy and HP had different meanings.

All the boats that you are looking at probably have raw water cooled singles. As long as they have not corroded to badly they will give you excellent service.

My guess is that you are really talking about money.
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Old 12-05-2008, 05:25   #9
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I believe that Yanmar still offers their 1GM10 - an 8 HP (cont. @ 3400 rpm) Single-Cylinder raw water cooled diesel.
Pat?
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Old 12-05-2008, 06:48   #10
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As Gord has said with addition that you will be very hard pressed to find a new raw water cooled engine.
Not sure Gord actually said that but be that as it may, Yanmar still do a 2GM20 raw water twin (or did as recently as recently a couple of years back).
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Old 12-05-2008, 07:52   #11
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Not sure Gord actually said that but be that as it may, Yanmar still do a 2GM20 raw water twin (or did as recently as recently a couple of years back).
Gord said:
"Most 27 - 36 Ft. cruisers, I've seen, will be equipped with 12 - 20 HP, 2-Cylinder diesels.
Most single-cylinder engines will be too small for these boats, under most circumstances."

And:
" I believe that Yanmar still offers their 1GM10 - an 8 HP (cont. @ 3400 rpm) Single-Cylinder raw water cooled diesel."
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Old 12-05-2008, 08:04   #12
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Opps, I think I misread Coopers post - sorry guys....
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Old 12-05-2008, 09:38   #13
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As of 2006 the GM series has been discontinued.
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Old 12-05-2008, 10:25   #14
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As of 2006 the GM series has been discontinued.

Cool deal. That must make my '83 6.5hp 1GM a valued collectors item, haha..
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Old 13-05-2008, 03:35   #15
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Yanmar in Australia still advertise the 1GM10 as a current model.
YANMAR Diesel Power - GM/YM Series Marine Engine
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