Freeze protection for small keel boat Universal M18

[yelkenli]

We had a debate on the need to have a heater in the boat to keep the engine from freezing.

This is a fresh water lake, and the water temperature low can reach 40 degrees F according to one source.
Forecasts are calling for air temperatures down to 15 degrees F next week.

Does anyone know what the engine compartment temperature might be in such conditions?
Is there a rule of thumb?

I would assume the answer depends on how air tight is the compartment. The shaft is a heat sink in the water, connected to the engine and exposed to the air for about a foot. But there are heat exchangers hanging in the air, and other weak points.

The boat will get sailed soon, so putting it out of commission for winterizing is not desired. And its an old Catalina 27, so I want to assume it has seen such conditions before and survived (though there is a leak at the heat exchange - freeze damage?). I do not know what the previous owner did - my assumption is nothing.

I am looking into a way to record the temperatures, but this would be after the fact.

 

[jssailem]

Sure. Somewhere between 15º and 40º would be my guess. The spaces above the water line will tend towards 15º, and below the water line trend to 40º.

During sustained extreme chill events in the PacificNW, I experienced a burst hose when some water from the emptied water heater was trapped in a low loop.

You can observe the current temperature and record the maximum temperature with one of these inexpensive units.

2
AcuRite 00986M...

 

[Davidasailor26]

Air temps down to 15 are pretty far below freezing. If it were me I’d feel better spending a few dollars on antifreeze and a few minutes sucking it through the engine. Cheap insurance compared to the alternative.

 

[Don S/V ILLusion]

Seems like a big chance of big damage for very little cost/effort to protect an engine. ”do you feel lucky?”

 

[dlochner]

For monitoring temperature take a look at the Ruuvi Sensors (Amazon link). I've been using one to monitor the refrigerator temperature. Cool device.

A gallon of Marine/RV (pink stuff) antifreeze is about $10. Takes about 10 minutes to winterize the engine. The freshwater system should be drained, especially any pumps or faucets. I'd just leave them empty until spring. Bring some bottled water if you get thirsty.

 

[BarryL]

Hi,

Do you have shore power? If so, hanging a 60W incandescent light in the engine compartment should provide enough heat to keep the engine room above freezing. If no shore power then I could run a few gallons of marine antifreeze through the engine raw water system. I ASSUME the engine coolant is in decent condition. If not, change it to fresh coolant.

Good luck,
Barry

 

[yelkenli]

I have shore power and will set up a light on a thermostat. I will also re-install two access covers that I removed to work in that area, and look for ways to reduce air flow generally.

I am not sure what fresh water is in the sink/head plumbing system, but good point. I will try to drain it, when I find it. I have not yet used it and don't plan to for fear of what might be growing in it.

If I can get a recorder, I will post the resulting temperatures.

 

[jssailem]

will set up a light on a thermostat

Use an Incandescent or a halogen light bulb. LEDs do not put out heat.

With the lines drained you might blow air into the hoses to empty any residual water.

 

[Rich 35.5]

I have shore power

Incandescent bulbs are getting hard to find in the US, and the 200W heat lamps are way too much heat. I use a ceramic heater meant for reptile enclosures. It might be 90W, but that is still a lot of heat in a small engine room. We usually leave the cover open a bit so it doesn't get too hot, and spreads the heat to the rest of the cabin.

 

[dlochner]

I'm not a big fan of leaving electric lights and heating devices plugged in and turned when the boat is unattended. Too easy for something to go awry with consequences you, the marina, and your marina neighbors would resent you for.

 

[shemandr]

To Dave's point I've seen many marina storage contracts which specifically prohibit heaters on boats either in or out of the water.

 

[LloydB]

I think i would be tempted to take my buck Rogers laser thermometer down to the boat that is sitting on a 40° automatic heater instead of my open air trailer and check the temperature difference between the general water temperature any actual engine temperature without doing anything until I figured out what was likely to freeze first. On the other hand I probably would leave a incandescent 60 Watt light bulb from the dollar store running in the engine compartment (outside hatches closed of course) without a hint of angst. After all all those chicken farmers couldn't be wrong.
Of course if i could pull the boat onto the top of the water where it might be drier I'm sure my attitude would change significantly.

 

[Project_Mayhem]

Go with the -100F antifreeze. Depending on how your boat is designed, you may have a hard time seeing the exhaust output. Autozone has Prestone brand -100 for $7/gallon.

If you want to keep an eye on things, you can also get a used 4g hotspot for $15, data only pre-paid SIM for $30 and a temperature probe for $15. I have not tested any of these products

 

[FastOlson]

Regarding the advice about using AC heaters, whether incandescent bulb or simple warm resistance types often overlooks a related problem. When/if the winter weather is cold enough to threaten the interior temperature of the boat, there is a real good chance that "severe weather" will also cut the power to the whole marina.
I would always advise a first line of defense as winterizing the engine. Our local RV store (and often the chandlers) will have "pink RV antifreeze" on sale every year for $4./gallon or a bit more. Just keep several gallons on hand. Our 3 cylinder diesel engine takes a tad over 3 quarts, drawn into the raw water system while the engine is running. I added a two way thru hull valve from ForeSpar, many years ago. It works great. The temporary hose from the valve into the gallon jug of "pink' sucks it in and when some pink shows in the discharge at the transom we shut the engine down and rotate the seacock valve to the "off" position.
As for the interior fresh water system, I run the 12 volt pump until it spits air. All that said we seldom get weather below 20 F for more than a week. Once every other year it gets down to 12 for a couple of days.
Other locales have more severe and lingering cold spells, so view this as just one more data point, and YMMV.
Link: https://www.forespar.com/pdf/freshWaterFlushApplicationSheet.pdf
(Note that they also have this valve assembly available in their stronger "series 93" seacock, and that's the version we have.)

 

[Tally Ho]

I would run a gallon or 2 of pink AF through the engine to be safe. You should also drain the potable water system, including the water heater. You could blow the lines clear or pump some pink AF though the potable water system to be sure the lines don't freeze. And if you have a marine head, you should pump a gallon of AF through the toilet as well (not just dumped in the bowl).

I would also close all of the thru hulls (should do this anyway).

Whether you use the boat again this winter or not, she should be ok in the cold for a few weeks.

Greg