PG or EG coolant in engine closed cooling system with water heater?

[sesmith]

New boat to me, Catalina 350 with Westerbeke M35b in it. First boat I've had with a water heater in it. Not sure what the engine coolant is in the engine closed cooling system. I do know that it is reddish or orange (so suspect dexcool). I do know that it tested to -50 on the EG scale on my refractometer and -30 on the PG side, so not concerned about it for winter, but will likely flush and replace it next season.

Since there's a water heater involved, should I be concerned about possible leaks into the fresh water system, and use one of the PG coolants like Starcool or Fleetguard's heavy duty PG coolant? Or should I just use one of the global EG coolants? Or something else? So many choices these days...

 

[dlochner]

Not too long ago there was this same discussion here.

First check with the engine manufacturer to see what they recommend. Yanmar recommends Dexcool, not sure about Westerbeke.

I'm of the opinion that there is very little risk of poisoning for several reasons. The leak would be into the HW tank which should have a check valve to prevent HW back flow into the fresh water tanks. Most people do not drink water from the HW tap, they prefer cold water. A large leak would be noticeable pretty quickly as the HW would be discolored and smell funny. It would also result in a loss of coolant which would be noticeable by the engine overheating. A slow leak would be the worst case scenario, you could detect it by periodically checking the coolant level and eventually by smell and color. The coolant would only leak when the pressure inside the heat exchange is greater than the pressure outside the heat exchanger.

 

[sesmith]

Thanks. Somehow I missed that discussion and didn't find it on the search I did. At least via the copy of the owner's manual I have, Westerbeke is pretty non-specific other than a 50-50 mix of "antifreeze" and distilled water.

They then give a mixed clue. There is a note to look for the "new environmentally-friendly long lasting coolant" (whatever that really means, assuming they mean PG product like Starcool). They then show a mix ration of 50% giving a freeze protection of -40 degrees F. That would imply EG, not PG.

 

[dlochner]

https://forums.sailboatowners.com/i...erra-pet-safe-antifreeze.193800/#post-1490295

 

[Tally Ho]

I am with @dlochner on this. I run EG in my Yanmar 2GM20F engine with engine-heated water heater.

Greg

 

[sesmith]

https://forums.sailboatowners.com/i...erra-pet-safe-antifreeze.193800/#post-1490295

Thanks for the link.

 

[BigEasy]

I use the coolant & concentration as recommended by Yanmar. For weekend cruises we usually use bottled water for consumption & water from the tanks for showering & cleanup. I realize that for long term cruisers and live aboard that bottled water wouldn’t be an option. If it is a concern, one could test for presence of coolant in the water heater out put.

 

[LakeOntario270]

I have a 1996 Westerbeke 20B Two that I flushed this year. I use Prestone Ready mix from Advance Auto. The old antifreeze came out looking fine (in for 4 years). The heat exchanger looked clean when I took the end cap off to fish out a broken impellor blade. There is nothing exotic about a Westerbeke engine.

 

[thinwater]

deleted

 

[Maine Sail]

Is this normal? My understanding is that boats with expansion tanks allow back flow to avoid over pressure. No much use in having the expansion tank, otherwise. It's a small amount, but there is no check valve on boats I've seen. There isn't a check valve in your house (would violate the building code).

In houses they call them "backflow preventers". Our local code enforcer requires them at the inlet feed to the dwelling and for any feed to a hydronic or steam boiler. On boats & RV's a check valve on the cold water feed to the water heater is just a normal installation practice.

If there is a leak in a water heaters HX you'll know it pretty quickly as your radiator cap on the engine will pop off whenever you turn on the vessels fresh water pump and you over-pressurize the coolant system.

 

[dlochner]

@thinwater, yes it is one way of installing a tank. Here's a schematic from Calder's book (3rd edition). Raritan uses a expansion tank with a check valve between the city water supply and the expansion tank. When Sabre built my boat, they used a check valve. Obviously it is important to have an appropriate and working pressure relief valve. Raritan recommends a 50 psi valve.

Without a check valve the whole plumbing system will act as an expansion tank, the HW will back up through the system and eventually find the water tank. That would not be a big problem, except it puts scalding hot water in the cold water hoses. If the cold water tap is opened it will pour forth with scalding water and not cold.