Is there any cooling advantage of a hot water heater?

[msalvucci]

Hi -

I am trying to decide if I should replace or just remove my corroding, engine-heated, seldom-used hot water heater. The heater is located in transom, and there is a considerable run of hose from the engine to the heater and back.

My question, does having the extra volume of coolant running through the loop and the element in the heater provide any additional cooling of the engine (Yanmar 3GM30F)? If the loop does aid in cooling, then replacing the heater seems like a wise move for performance and resale. If the loop does not affect cooling, then removing the heater entirely and looping the out and in at the engine seems like a way to simplify and remove a potential leak source.

Thanks in advance for your expert opinion.

Mike
SV Zephyr
Chula Vista, CA

[steve77]

The water heater and the associated plumbing do remove some heat from the engine. It is this transfer of heat that makes the water heater full of hot water. However, your Yanmar will not overheat if the water heater is removed. The cooling system is designed to operate without the water heater.

If you don't need hot water aboard, you will not damage your engine by removing the hot water heater.

Cheers!

Steve

[a64pilot]

It provides additional cooling, until the water temp in the heater and the engine coolant reach equilibrium, after that due to the insulation in the heater, there is very little if any additional cooling.
If you remove it, I seriously doubt you'll notice any difference at all in the engine temp, since a healthy cooling system has an excessive capacity, and temps are controlled by the thermostat

[msalvucci]

Thanks a64pilot and steve77 for the information. Since there is no real advantage in terms of engine cooling, I inclined to remove the heater entirely.

Best wishes,

Mike
SV Zephyr
Chula Vista, CA

[Mediator]

While you've already made your decision, I will add that when I needed full engine power for a critical situation and my Perkins overheated, I ran the hot water and it did make a difference (until I cleaned the heat exchanger and solved the problem entirely).

But the above posts are correct, you shouldn't need a hot water heater to aid in cooling.

[a64pilot]

Originally Posted by Mediator

While you've already made your decision, I will add that when I needed full engine power for a critical situation and my Perkins overheated, I ran the hot water and it did make a difference (until I cleaned the heat exchanger and solved the problem entirely).

But the above posts are correct, you shouldn't need a hot water heater to aid in cooling.

You can do similar in a car that is beginning to overheat, turn the heater on full helps a little.
Of course it cooks you inside, cause most likely it’s overheating on the hottest day of the year.

[msalvucci]

Originally Posted by a64pilot

You can do similar in a car that is beginning to overheat, turn the heater on full helps a little.
Of course it cooks you inside, cause most likely it’s overheating on the hottest day of the year.

We live in Phoenix, so we would bake long before the car engine cools.

Anyway, it is good to know that running the hot water on the boat would help cool the engine in a pinch. Thanks for the tip.

My wife favors replacing the heater, so you can guess which direction I am now leaning.

Mike
SV Zephyr
Chula Vista

[CaptTom]

I still think "free" hot water from waste engine heat is one of the small joys of cruising.

I'd never think of it as cooling the engine much, though. Not much heat exchanger surface there, and as was pointed out, it's insulated. Far more likely you'll pop a hose or connector and overheat the engine. I did once. No big deal, fixed the chafed hose, refilled the coolant and was on my way. I still love having the water heater loop.

[AKA-None]

I second the free hot water

[S/V Alchemy]

Originally Posted by Mediator

While you've already made your decision, I will add that when I needed full engine power for a critical situation and my Perkins overheated, I ran the hot water and it did make a difference (until I cleaned the heat exchanger and solved the problem entirely).

But the above posts are correct, you shouldn't need a hot water heater to aid in cooling.

Interesting...so you essentially ran the hot water down the sinks and it performed like a radiator? Seems logical, if (as you indicate) it was a solution to a different problem you had with a clogged heat exchanger.

[Alita49DS]

Your wife is perhaps the sensible one.

Who wants to wash up in cold water? Let alone shower. Or shave.

If I were even to raise removing the hot water cylinder there would be a mutiny on board. And I would rapidly concede that the mutineer was entirely right.

[Dooglas]

The correct answer is that these are two different issues. No one installs a hot water heater in order to cool their main engine. You install (or replace) a hot water heater because you want hot water. You rebuild your engine cooling system when it loses efficiency due to a corroded or partially blocked heat exchanger, or you have a failing/failed raw water or freshwater pump.

[Djarraluda]

There is an issue nobody has mentioned yet - the cooling water off take and return will probably (normally) be associated with an arrangement that creates a by-pass of the thermostat.
You need some flow through the system or you need to re-plumb the engine to take away the bypass arrangement.
Check the Yanmar agent for work needed if you just shut-off, or pipe a bypass there.
Roger

[jkindredpdx]

I didn't use hot water from my old rusted water heater nearly as much as I do with my new one. I really enjoy having free hot water for dishes and a warm shower.

[RaymondR]

I bathed out of a bucket in the cockpit on my last boat for about 16 years whilst the one I have now has a hot water system and I would not go back to the old bucket system.

However I now spend a great deal of time dreaming up cunning systems which would allow me to take a shower without running the main engine for half an hour to heat up the hot water systems.