Keeping the engine bay above freezing this winter

Sheppy

Sheppy

Well-Known Member
Joined
17 Jan 2011
Messages
437
Location
Devon
Visit site
I’m starting to give some thought to winter and as I’m not taking her out of the water I want to make sure I don’t have any water freezing issues.

She has a closed water cooled Mercruiser 165 diesel so antifreeze should be ok, but I’m concerned about the intercooled raw water system. Although I’m in estuary waters with quite a bit of salt I don’t want to take any undue risks.

I can’t really afford any of the diesel heating systems (although I am keeping an eye out for pre-owned) so am looking for a more creative solution to keeping my engine bay above freezing over the winter months. I have a few ideas involving 12v heating systems, constant rotation of heating battery, solar charging etc. but wanted to know if anyone has any good viable/creative suggestions. My engine bay isn't large, about 3m cubed in size.

I’m ok with the other aspects, running the pressurised water system dry, transom show etc., I just want to find a sensible solution for the engine bay.

Thanks,
John
 
Last edited:
How accessible is your boat to you? Is there shore power available? Greenhouse/cold frame heaters, e.g. tube heater, paraffin heater should do it...
 
If you have shore power, use a low wattage tube heater with a thermostat socket that you connect to the main. It has worked well for me so far ( 2 winter seasons in the water).
 
As far as I see, the biggest challenge is to reduce risk of chill transfer from ice and cool surface water..

So ..... as small air pump with a perforated hose submerged in a circle around the boat giving out a small stream of air bubbles keeping the are around the boat ice free...
 
Thanks guys,

I'm not overly concerned with the estuary water freezing due to the amount of salt, only what’s left in the raw water cooling heat exchange system. Assuming heating via a 12v supply isn't going to be practical, does anyone know of any small oil or paraffin heaters that might do the trick?

John
 
I wouldn't want a paraffin heater in my boat if it was on an estuary, unless there was some way of making sure 100% that a passing wake wouldn't cause it to tip over ... and ... whoomph :eek:

I would have it lifted out somewhere onto a hard standing, connect up a 240v cable, and stick a couple tube heaters inside.
 
Thanks FP,

Most modern paraffin/oil heaters have auto cut-off switches should they topple over:
http://www.dry-it-out.com/corona-rx2385-3kw-liquid-fuel-heater

But I’d prefer a 12v heater to just blow warm air into the engine bay running off a thermostat but it seems difficult to find something that'll run for about week on a single large battery. Still, hopefully I've got plenty of time to resolve something.

John
 
The only 12v ones I know of are the 150 or 200w windscreen demister ones that there are dozens of on ebay. Whether they would make enough of a difference to keep frost at bay without flattening batteries I doubt. Cheap enough to experiment with though..
 
I think most of the sea water will drain out through the leg when you lift it out.
Other than that, just drain/blow the water out of the rest of the sea-side of the system. Some say pump antifreeze through, but I think maybe that is in case you are at -50 in Finland.
If you get the sea water out, you dont need to waste time on heating...
 
If you're keeping her in the water then the water itself will provide the warmth to stop the freezing, it will probably not drop below about 6 degrees C. It's the air that you need to be concerned about, put a good cover over the boat and/or a thick blanket over the engine.

Carry out all the other usual precautions that you've mentioned such as antifreeze, emptying fresh water hoses etc and you'll be fine. I've had unheated boats in over winter for 20 odd years without any problems, all within 20 miles of where you are now.
 
Thanks LJS,

I'm actually just up around the corner from you and do agree that I'm probably worrying too much, only I have a new-to-me boat and things are suddenly all a bit different to what I'm used to. I do believe boats are better protected from the cold when on the water as opposed to the hard but just wanted to avoid any silly costly errors. Stupidly, I hadn't actually thought about just wrapping up the engine and water system in blankets/old duvets but I suspect that would work perfectly and with zero hassle/worry too.

Thanks,
John
 
wrapping engines in old duvets is good but also block the air vents into the engine compartment to further reduce cold air getting near the blocks/heat exchangers.

But leave a note on the helm to remind you to remove them when you next use the boat
 
RIN said:
wrapping engines in old duvets is good but also block the air vents into the engine compartment to further reduce cold air getting near the blocks/heat exchangers.

But leave a note on the helm to remind you to remove them when you next use the boat
Click to expand...

Im sorry but I totally disagree . NEVER close the inlets - what is needed is as much fresh air as possible - whether its minus or not is not of importance.
Id say listen to Longjohnsilver in this case.

I have had boats stuck in ice for months, living onboard in week ends, and even that is not a problem. Just make sure there is no freshwater left in the tubes/piles when boat is left unheated - and drain SW from engine. At that time I had mercruiser with sterndrive - but a seawaterstrainer. If you have this you can always run antifreeze through SW part of engine as well.

Dont worry too much !
 
Advice I was given to prevent freezing of raw water system was to shut sea cocks, remove raw water cap, start engine and continually top up raw water system with a fresh water/antifreeze solution until it is seen to exit the outlet. Then switch engine off and replace cap
Raw water system will then contain the fresh water AF solution until opening sea cocks and re-starting. Needs to be repeated once starting engines with sea cocks open. Sounds a logical effective process for boats layed up for the longer term. Unsure what todo if its only for a few days at low temp with ice around other than to provide heat to the engine bay one way or another.
 
SC500 said:
Advice I was given to prevent freezing of raw water system was to shut sea cocks, remove raw water cap, start engine and continually top up raw water system with a fresh water/antifreeze solution until it is seen to exit the outlet. Then switch engine off and replace cap
Raw water system will then contain the fresh water AF solution until opening sea cocks and re-starting. Needs to be repeated once starting engines with sea cocks open. Sounds a logical effective process for boats layed up for the longer term. Unsure what todo if its only for a few days at low temp with ice around other than to provide heat to the engine bay one way or another.
Click to expand...

Yes this works - but I wasnt sure whether you had seacocks and Seawater strainer fitted between sterndrive and engine.
 
I would doubt it would get cold enough in the boat to freeze fresh water never mind salt. My boat was in the water through last winter (used regularly), I don't recall the fresh water tank freezing. I have had a boat with no antifreeze in the closed cooling system in the water through the winter in previous years with no problems.
 
gordmac said:
I would doubt it would get cold enough in the boat to freeze fresh water never mind salt. My boat was in the water through last winter (used regularly), I don't recall the fresh water tank freezing. I have had a boat with no antifreeze in the closed cooling system in the water through the winter in previous years with no problems.
Click to expand...

Don't count on it. A quick google for frost damaged boat engines will soon put you straight.

It's one of those things that you will probably get away with for years and then one particularlt cold snap will catch a few out.

I would take action every year to prevent frost damage whether that is to winterise the engine or add some low level heat. Winterising is a hassle but the cost of a new engine puts it into perspective IMO.
 
Never had any heat in the engine bay. Engine is full of 50/50 water/antifreeze. Raw water system is full of salt water, or at the moment brackish. Boat is in the water. We obviously drain the freshwater system.

Couple of Winters ago, when it was really cold and we had all of that snow, we went down to the boat and the snow had blown up the back of the patio doors, half thawed, more snow, re-frozen etc etc. Was two feet or more up the doors and all over the locker cover, se i couldn't get to any tools. Took a while to get in, the 4 litre bottle of drinking water standing in the shower was unfrozen. I didn't actually look, but i guessed the engine wasn't frozen either :)

My engine is in the bottom of the boat, midships. The engine compartment has a GRP liner, which is covered with 2" of sound insulation, but there are some large air vents, which i leave uncovered. I don't cover the engine with anything, rather have the air movement i think.

We use our boat through the Winter, though not a lot. If we were not going to use it, i might be tempted to get some antifreeze in the raw circuit, maybe, perhaps, possibly...............
 
I agree with Neale. A couple of winters ago, about half a dozen or so boats sank at our marina, due to ice cracking either the cooling system or sea cocks. V8 petrol engines suffered the worst.

OK we are in freshwater, and the marina froze for 42 days, coldest -19C, and you wont get anything this harsh on the coast. For about £100 you can equip with sufficient tube heaters and thermo plugs to get you through the winter, plus electickery costs of circa £25. Compared to the consequences of freezing, this is good value IMHO.
 
You must log in or register to reply here.

Other threads that may be of interest

Bouba
Port-Cros tomorrow
Replies
17
Views
455
potentillaCO32
P

Share this page

Top