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Can you run the engine with the water tank empty?

u079721

Contributing Partner
Here's the background.

Every year I winterize my water system on my 1989 E-38 by disconnecting the water from, and bypassing, the water heater tank. Then every spring I hook it back up again. We typically never use the hot water aboard, so after a while of constantly being heated by running the engine, the tank begins to smell foul (that sulfur odor). Cleaning with bleach gets rid of the odor, but it will come back next season.

The last couple of seasons I have decided not to hook the water up to the heater until right before our cruise. So for a couple of months I am running the engine without water in the tank.

So what's the big deal? Well, in the manual it states: "DO NOT....RUN THE ENGINE UNTIL [the tank] HAS BEEN FILLED. THE....ENGINE WILL OVERHEAT IF THE TANK IS DRY."

Now I can tell you that my engine always runs about 170 degrees, whether or not the tank is filled. And frankly, since there is a heat enchanger on the cooling system, I can't figure out why it should matter whether the water tank is full of water or not.

Since we don't even use the hot water on our cruise I was thinking of not hooking up the water to the tank at all this season. But I am a bit more reluctant to try that since our cruise usually involves a 25 hour motor at each end, which might stress the system a bit more than my typical pre-cruise 30 min of motoring each way for my day sails.

Does this warning make sense to anyone? Anybody know if it matters?
 

Loren Beach

O34 - Portland, OR
Senior Moderator
Blogs Author
If your boat did not have an engine-heat exchanger in its hot water tank, like many production boats, the engine should be cooled just fine by its own "heat exchanger".
I have never heard of any such warning. When I added a fan-driven heater unit to the closed-cooling side of the engine system, I put it in series with the hose that went to the hot water tank coils. This slightly increased the total warmup time for the engine, but not by much.
I would look at the situation this way: once you have the whole six gallons of drinking water in the tank up to engine temperature, no more heat can be transferred from the coolant, anyway --- and from then on it is as though the tank was not in the system. Same thing with tank empty and coils surrounded with air...

We run the engine with the hot water tank dry in the spring, when we paraded around for an hour for Opening Day. No heating issues.

Our tank is SS, inner and outer shell, and has no taste of any kind... I did replace the original tank.
(FWIW)

Best,
Loren in PDX
Olson 34, Universal M25XP 3 cylinder
 
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Sailsteve

Member
Last year when laying up the boat for the winter I neglected to drain the hot water tank. The water in it froze and ruptured the tank causing a big leak into the bilge when I filled the water tanks. I disconnected the water heater from the fresh water system. The HW tank is totally dry and I have been running the engine for many hours at a time with seemingly no ill effect on temperature. So, I would guess that the HW tank has little effect on engine temp.

Steve
 

clohman

Member II
The warning in my owners manual reminds not to apply SHORE POWER voltage to the heater without water, i.e. by turning on the 120 VOLT panel switch. I have run mine each year without water in the heater without incident.
 
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