Will my tube heater keep engine above freezing?

[SimonA]

It was unexpectedly cold last night, around minus 6 where my boat is. It's in fresh water, I have a 180w 3ft tube heater which runs the complete length under the engine and it's a small engine bay with ventilation into the cockpit and without any vents directly outside . I'm slightly worried about it as the temperature has been so low overnight.

I was thinking of putting an old duvet over the engine or maybe adding a second heater. Am I worying for no reason?

 

[sailorman]

what do you put under your car sitting outside the house.

 

[neale]

what do you put under your car sitting outside the house.

Surely you understand the difference and that's not a serious question!

The answer is difficult to say. Greenhouse heaters will help keep the engine bay above freezing but there are too many variables to say whether 180w in your size engine bay is enough.

Best thing to do it to winterise the engine properly to remove the worry or maybe get some sort of temperature monitoring and alert system to warn you if temps are getting too low. Trouble with the latter is, what do you do if you get an alert in the middle of the night?

On fresh way in particular, winterising really is the best answer.

 

[SimonA]

Just as well I went to check, the power to all the marina has been off since yesterday. It was minus 5 in the cabin but a bottle of water hadn't frozen in the engine bay, so hopefully all ok.

 

[Davegriff]

I wouldn't worry too much. As has been pointed out, you don't put heaters under car which is probably subject to far lower temperatures with the added chilling effect of wind. I often leave my raw water cooled engine unheated in less than -6C without harm, and imagine its spent most of its life that way (c35 years). Presumably yours has anti-freeze in it anyway.

I think its been discussed on here before regarding the phenomenon of boat engines in boats left afloat being left seemingly unaffected in quite big temperature drops.

Hope its ok anyway.

 

[CLB]

As has been pointed out, you don't put heaters under car which is probably subject to far lower temperatures with the added chilling effect of wind.

Seriously, do you not understand the difference between a car engines cooling system and that on a boat?

 

[Alpha22]

Seriously, do you not understand the difference between a car engines cooling system and that on a boat?

Simple.......

Car - All the water has antifreeze in it. It will not freeze.
Boat - The sea/fresh water cooling circuit does NOT have antifreeze in it... it can't normally - it is the sea/river. Without sealing the system and introducing anti freeze or providing an external source of heat, it can freeze. (with fairly spectacular results - usually sinking the boat!!)

Hopefully that helps.

 

[kashurst]

Best thing to do is winterise your engine - they can and do freeze with very expensive results. You can get slight cracking in intercoolers that is not immediately apparent but water will slowly get into the engine and wreck it later on.
It's not difficult and you can sleep at night and not be reliant on an electricity supply you have no control over.
A few years back I was moored on a river in fresh water and eight boat engines were wrecked by spring. On one partiicular night, it was getting cold and all the boats with electric heaters turned on - the sudden rush took out the supply to the marina.
No doubt someone will point out that seawater freezes at a lower temperature - it does at -2C

 

[l'escargot]

Did the fresh water the boat was sitting in freeze?

 

[Momac]

Am I worying for no reason?

I hope it is good enough since I have the same and I am further North.
If the boat is in the water and the water is liquid it will keep the engine bay sufficiently warm.
I have see far more severe ice in previous winters with no issues.

 

[SimonA]

Did the fresh water the boat was sitting in freeze?

Yes Marina frozen solid. A pan of water I'd left in the cabin frozen into a block and the thermometer said minus 5 , yet a container of water on the cabin floor hadn't frozen and neither had a bottle of water in the engine bay. It seems anything close to the water line hadn't frozen.

I don't fully winterise the boat as I use it in the winter. I don't have a big lump of an engine with intercoolers, it's just a little BMC 1.5.

 

[ontheplane]

Keep your tube heater on all the time, but add an oil filled radiator on a thermostat switch which will come on at 1 deg and go off again at about 3deg - then if the tube heater struggles it will kick in, but not all the time.

 

[Greg2]

I tend to think that it has to be very cold for a long time before you are in danger of the engine bay dropping below freezing point. The boat is sitting in water, which is usually above freezing and effectively helps keep the engine bay above freezing point. The real danger time is when the boat is out of the water and surrounded by air with a temperature below freezing so would always winterise before lift-out.

Would not argue with those that prefer to take precautions by winterising when the boat is in the water but just offering some reassurance to the OP that a single night at a low temperature is unlikely to cause a problem.

 

[rafiki_]

My previous boat was on freshwater, and a few years ago the marina recorded -19c. The marina was frozen up for more than 40 days. I used 180w tube heater in the engine bay, and the same in the saloon. I put old sleeping bags over the engines, and all was fine. The bigger concern was the domestic water system, but I drained this fully, and used a dinghy foot pump to blow the water out of the calorifier, which did not drain on its own.