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Winterisation List Author Andy Banner

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Posted 08 November 2014 - 08:28 AM

Winterising may be "Propper Easy" as Griff says, if you have the wherewithall to do it.

Driving is propper easy, unless you can't drive.

Here is a list of things you should consider

Change the engine oil

Drain the coolant from the engine or top up with compatible antifreeze

Drain Raw water from the engine's cooling circuit or run seasafe antifreze though until you see it come through the exhaust.

If you drained the engine in above step, ensure you also fully drain the exhaust waterlock too.

Ideally, coat the engine in a mist spray of WD40 or similar oil to prevent rust building up.

Drain all the water tanks.

Disconnect the main water pump and take it home

Drain any sink or shower traps

Disconnect shower pumps and take them home

Pump out the toilets

Turn off all raw water stopcocks and drain the hoses connected - if not in the water, disconnect the hoses and drain; operate the sea cock a few times to remove any trapped water and leave closed.

Install moisture traps everywhere to reduce condensation

Leave plenty of ventilation in the boat and wipe bulkheads, walls, ceilings and so on with an antibac solution to help prevent mould growth. Remember to check under pelmets and on the roofs of cupboards and shelves.

Fill fuel tanks to the brim to leave no space for condensation to form.

Remove the curtains and soft furnishings and take them home. Not a bad idea to remove carpets too if possible.

Give the boat a good clean. Any algae present now will promote winter growth.

A propper job is not quick, but anything other than a propper job is likely to lead to a degree of regret and likely cost at the beginning of the new season.

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  • 2 weeks later...

Having read a lot of information I've come to the conclusion a lot of it comes down to common sense  - stop things being able to freeze basically.


Now let see if I have this correct - wrong, too much or what others may think - but If was myself I would:


1. Change the coolant on the sealed side of the engine first - this means flushing it out and then adding premixed or at least 50/50 mix of antifreeze to water. Inspect header tank pressure cap - replace if spring or seal are not in good shape.   Because there may be air bubbles once this has been flushed, it is a good idea to run the engine - as it warms up (with the expansion tank cap off) the coolant level may drop or air bubbles may be allowed out.  Replace cap.


2. Now the engine is warmed through, stop it and change the oil.  Because it is warm the oil will flow freely - drain the oil first, then the undo the oil filter - put a large plastic bag over the filter and a rag under to catch any oil and be able to neatly seal the old filter in a bag.  With new oil smear the rubber seal on the new oil filter and screw back on firmly but never use a tool or put it on overly tight.  Next up change the fuel filters - doing so may require the bleeding of the fuel system  - engine manuals will give details of how this is done and procedures to go through, always handy to know just in case you needed to do it one day 'in the wild' say due to contaminated fuel or a blocked filter.


By now the engine should be cool enough to give the coolant level another check and top up as required.


3. Run antifreeze through the raw cooling side of the engine - you can use a bucket with 50/50 mix of antifreeze and water (use eco friendly stuff for this) remove one end of the hose from the raw water pump - that leads to your seacock/raw water filter - and replace with a short length of hose to the bucket.  Start engine.  The coolant mix will now be sucked from the bucket, through the raw cooling side of the engine and out the exhaust.  A full bucket should be plenty to thoroughly go though the engine - the moment the bucket is getting close to empty turn off the engine.


4. Now check the impeller of the raw water pump  - some say change each season, others say every second either way never leave it in situ over the winter as it will 'mold' itself to a single shape so take it out.  Leave a note that you have done this.


5. Now you can remove the short hose from the bucket to water pump,  and replace the main hose which goes from your water pump to your seacock  and raw water filter.  Turn off all seacock's.  Use a 'turkey baster' to suck  water from the tube that leads to your thru hull fitting or under the filter screen in your 'Vetus style' raw water filter.  Now fill with 50/50 antifreeze solution - replace all seals and leave a note reminding you the seacock's are all in the off position.


6. Now move to your engine's gear box - if you have a PMR hydraulic type, these usually will use engine oil, but make sure you know what viscosity - of course would be great if it happened to be the same as your engine but if it is not stick to what the manual asks for.  Drain the gearbox oil into a suitable container, fill with the correct amount of fresh oil.  Now for the propeller shaft and stern gland, if it is an auto greaser then ensure topped up with good quality grease and give it a few turns to push some grease through, make sure the gland nut is tight so there is minimal water ingress, just a drip every couple of seconds - it may be worth spending more for something that is partially good at dealing with high heat/friction and stays stable even with salt water.


7. Generally go over the engine and clean - keep the bilges clean to, just some soapy warm water and a sponge will d wonders.  I would not mist the engine and parts with spray oil as this would help attract dirt which will then stick and build up over time, instead spray into kitchen towel and just rub over parts which may be more susceptible to corrosion - also check things like throttle cables and any linkages for signs of wear, corrosion or looseness.


8. Check batteries - are there any obvious signs on the outside - cracks in plastic body, bulges etc? Is the electrolyte topped up? are the terminals clean and corrosion free and are all wires attached thereto tight and in good order? It is worth investing in a battery metre and 'drop tester' to get a better idea of what state the batteries are in, if one is quite a bit different to others replacement should be considered next season.  If you have a 'smart' battery charger this should be used to keep the batteries fully charged and compensate for any power the bilge pump may use.


9. Turn off the gas at the bottles. Consider detaching the gas lines and storing the disconnected connecter in a small sealed bag - pop in a small bag of Silica to keep the damp out (these are often found with new shoes or small electrical items) but can also be bought online.


10. Now drain your fresh water tanks - this in turn should also drain down your hot water tank - of course there can be a small amount of water left in nooks and crannies but in the main this should deal with the largest risk.  Disconnect the water hose to the water pump from your tanks, and connect a temporary hose leading to your trusty bucket. Using some eco friendly antifreeze mix fill the bucket and now turn on all the taps and the shower head too.  Now run the water pump until the bucket is empty.  It is preferred  if you have a helper who can turn off the taps and shower head mid flow, this will ensure your domestic water pipes are now full of antifreeze mix - your shower tray also should have a couple of litres in it - a quick blast of the shower pump to drain but keep it short, you want to leave some of the mix in the pipe/pump assembly from shower tray to hull fitting to protect this. Turn off water pump at the breaker panel and reconnect your main hose from your fresh water tanks ready to go next season.  Leave a note to remind you to flush the pipes and not try and fill the kettle right away!


11. You should prior to all the above on the return of your last trip of the season have had the toilet holding tank emptied - and the fuel tank filled.  You might want to add some fuel stabiliser to keep it 'fresh' and further add in preventing the formulation of diesel bug.  I'd then also use a couple of litres of antifreeze mix pumped thru the heads - enough to make to the tank, but really to be allowed to sit in the pipes leading to the waste tank, the bowl and the pump assembly be it mechanical or eclectic to remove risk of any water remaining freezing.


12. As far as interior work goes that depends on what you want to leave or not - some remove all items some do not, what is a good idea would be the use of good quality vacuum storage bags for things like curtains and seat cushions.  Cheap pound shop ones tend to leak air, good quality ones don't. raise all foam seating and mattresses - using left over caps off of things like deodorants is a good idea so you have a couple of inches air space under things or behind things, open drawers and cupboards and consider moisture traps  in small confined areas. 


13. Remove all foods that might attract vermin - wash the interior of the fridge with some water and baking soda - you can use this mix for other non porous surfaces too or your favourite antibacterial wipes/spray.


14. Wash the outside of the boat - again the baking soda is a good eco friendly way of cleaning but further is a good anti bacterial action too but it won't kill things like Salmonella, E. coli  and Staphylococcus.  Furthermore ensure it is 'well mixed' as if not it has slight abrasive properties. Once dry consider polishing the boat which will mean it has a layer of protection and help stop dreaded 'green boat' syndrome and make getting rid of such come next seasons easier.

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In the vast majority of cases, you have to suck the oil out of a marine engine as you can't get anything under it to collect the waste oil. Many engines have a pump for this purpose. Some don't so you'll have to buy or borrow one or get a boatyard to do the job.


Draining the water tanks will not drain the hot water tank. The pump relies on water in order to push water through the hot water tank; water in means you will get water out. No water in, means no pressure/force to get water out. The hot water tank should be drained manually. AND, be careful with this too as the tank should have a non-return valve fitted to the inlet, so this will need removing too. 

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See...This is the difference to collecting information from all over the web and someone who actually does it :)


I’ve also seen videos where they put 4 gallons of anti freeze into the water tank, fill with water then run until comes through both the cold and hot tapes.  Not too sure how happy I’d be with the time it would take come seasons start to flush all that antifreeze out of the tanks.

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I have just acquired a vacuum pump and reservoir for removing the old engine oil. it has a pipe that one sticks down the dipstick tube after which it's just a sucking jobbie.

The real reason I bought it was to..... NO Peter & Timbo, behave yourselves!!... I bought it to assist in the bleeding of the engine if I have to replace my fuel filters. After watching the engineer at Whispering Reeds do this job it was apparent that a sucky thing was just the job.


One of the few disadvantages of using Biodiesel is that fuel filters need changing more frequently. A small price to pay!

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See...This is the difference to collecting information from all over the web and someone who actually does it :)


I’ve also seen videos where they put 4 gallons of anti freeze into the water tank, fill with water then run until comes through both the cold and hot tapes.  Not too sure how happy I’d be with the time it would take come seasons start to flush all that antifreeze out of the tanks.

Hi Robin,


I think you would never get rid of it no matter how much flushing of the tanks and pipes you did. A few years ago our management company at the time before we became self managed, decided to flush the tanks with some form of steralizing solution. for years we always could smell it when opening a tap and this is the main reason we suggested using bottled water for drinks on board.




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As Alan mentions you really cant get rid of it.


I have used Milton at the start of the season to sterilize the fresh water tank and it really does linger no matter how often you empty it.


We always use bottled water for drinking even with a water filter on the tap.


Does dry your skin out as well when you wash in it, but would rather that than catch some nasty water borne bug

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Milton -  long long time since babies featured in my life.        Using them in this instance would you use tablets or the liquid?


We use bottled water to drink but use the water on the boat to wash up and to put into saucepans to boil water for veg etc.      Does Milton linger in the water when using it for the veggies?


May be someone on here uses something other than Milton.

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Hi Monica,


I would not use the boats water for cooking, ok with the washing up etc.


We usually bring down a couple of 5 litre bottle of water, when we have used one up we usually fill this up direct from our moorings tap or do the same at taps on the 24 hour moorings that have them. this bottle we just use for cooking and leave any fresh bottled water for drinking & cleaning teeth.


We tend to do exactly the same on our canal trips.




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I use the liquid.

Like Alan we have a 5 litre can for using in the kettle and I have to confess never cooked a veg on board other than on the BBQ. Peas can be a problem though.

Packs of bottled water from the supermarket for drinking as we find the small bottles more convenient. Whatever is on offer.

I wouldn't have that much of a problem using the tank water on a hire boat for the kettle or cooking though as it gets refreshed a lot more often than our own boat. Would still use bottled for normal drinking though.

I know you can buy special treatments that are not cheap and filters that remove microbes Etc but they are expensive and the filters still have to be replaced fairly often.

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There is a food-safe anti-freeze that you can buy, but it is expensive and I really can't see the need for the expense when draining the system isn't too difficult in general; but having said that, our fleet boats are plumbed with this in mind to make it simple. Private boats may not be quite so easy. 


Tank sterilisation is an important part of recommissioning a water system. Milton isn't at all ideal. There are proper products for the job that don't leave an impression after a couple of full tank flushes.


The advice we give to all hirers (under Health & Safety direction, I might add) is do not drink the tanked water directly from the tap as the quality cannot be guaranteed. It is fine for boiling and washing.

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  • 11 months later...

It's getting close to that time of year again. Winterisation can be a real chore. 

There's a lot of advise and ideas here which will get you going. 

A few more: 

Change fuel filters and withdraw the glow plugs from diesel engines, decoke and refit (as Clive pointed out I had missed these). 

It's a good idea too to check your prop-shaft couplings for damage, wear, cracks and so on; better to know now that you might need attention next year than delay your use of the boat. 

Mould will grow very quickly in a damp environment, so ensure that you empty the bilges (ideally, clean them too). 

Clean out any crud around the tops of exposed deck lockers, rod drain holes (particularly in the gas bins). 

Can you cover the boat with a tarpaulin? Something that's not shrink wrapped will create moisture between the layers, so place timber stand-off pieces to allow air-flow. Ensure that it's very well tied down and that the wind can't get under and trip the tarp to shreds. 

If the boat is to remain afloat, check ropes, cleats and consider increasing fendering. If you're in an area where the river, dyke, etc is likely to freeze, floating tethered planks around the hull may help to keep the water around the hull from freezing and damaging. 



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The advice to keep fuel tanks filled over the Winter to avoid condensation has been around for a long time.

It's not as clear cut as it used to be though, with the chemical changes in modern diesel and it's shorter shelf life and chances of bio growth.

If you google something like "winter diesel storage condensation myth", you'll find dozens of hits from respected sources, like:




It should also be born in mind that it's perhaps not a very good idea for petrol boats with large tanks like mine.  Buying 200 litres of petrol and then not using it for 5 months is bad enough, but it would then also be strongly diluting any fresh fill-ups in the Spring for months afterwards.

I've always preferred to keep my diesel and petrol as fresh as possible (even with the use of additives), and then rely upon the large water separators that I always have in my boats, petrol or diesel.

Surprisingly too, I've only ever had to drain off very small amounts of condensed water from them, over fifteen years of winterising my various boats. As many other people seem to have found, going by those google searches.

One of my ex-hire boats had a 50 gallon steel tank, and I fitted a drain tap to the bottom of it, (with BSS cap etc.), and I used to only keep about 5 gallons in it over the Winter, and yet each Spring when I opened the drain tap, only half a cup of water came out before the diesel.


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I may just have been lucky but I have never found any water in the trap or any signs of diesel bug or other sediment. I have a 175 litre fuel tank and probably use about 400 litres per year. I normally keep it topped up in the Winter and then allow it to run fairly low during the Summertime. I do annual filter changes. My boat has two, one with the water trap and another closer to the engine and never any sign of contamination unless it is well buried in the filter where I cannot see it.

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Interesting this should pop up again and talk about condensation and forming. 

The theory goes that if you had a metal tank half full of fuel, the air gap above the level of fuel will cool as the tank does, and because the tank being metal is a great heat conductor it will get very cold but the heavy fuel will act as a sort of insulator.  This means that above the fuel level along the top and sides of the tank the air is able to condense on the tank walls and then drip or run down onto the fuel itself.

The less fuel in the tank so the great area where condensation can form, and so the great amount of water that may get in the fuel.

I’ve seen so many arguments and counter arguments it is hard to see the wood for the trees on this point but as others state, it is small amounts of water anyway.  I guess the main factor is if you had a mild steel or galvanised tank the more water inside it over time the greater the chance of rust and eventual leakage or contamination of fuel. 

I have been reading about Polyethylene fuel tanks, which because are less efficient heat conductors do not cause as much risk of condensation – but more over, are lighter weight and will never rot or rust.

Increasingly, cars have such fuel tanks fitted (yet lorries do not - sticking with metal) and while homes now have plastic water tanks in their lofts, boats still stick in the main to metal to hold water or waste which seems somehow odd considering societies love of plastic! 

I think there is a lot therefore to be said about plastic tanks, also that one can then use devises to give very precise level information of what is inside these tanks which use ultrasound to do the job rather than something physically the tank to provide information.

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59 minutes ago, LondonRascal said:

.......I think there is a lot therefore to be said about plastic tanks.....

They're more tricky with regard to the BSS testing though.

A number of years ago I was very keen on fitting a Vetus plastic tank which was built specifically for use in boats, even seagoing craft.

They were translucent, so the ultimate in simplicity for seeing how full they were.

I just couldn't get a straight answer out of the BSS head office in Rickmansworth though, with them quoting vague "approval" standards at that time.

Maybe it's more straightforward now, as that was right at the start of the BSS testing Nationally, about 15 years ago.

The amount of condensation possible in a partially filled metal tank is very small as well, as those links that I posted verify.

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Random question here..

Hopefully Orca will be afloat for the winter months (Yeah I can dream)... we have always winterised our boats over the winter but Orca has heating so she should be usable in the winter (and one reason we went for her and the hardtop).

What's the advise for keeping a boat in a running state over the winter. Should it really be winterised every time it's left? (P.s I don't like the idea of leaving heaters on when left unattended as we aren't local).

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I make sure the coolant has enough anti-freeze and keep a tube heater in the engine bay with a thermostat set to 7 degrees. I'm lucky in so far as both the water tank and the foul tank are housed within the extremities of the engine bay so benefit from the tube heater. I also make sure the water pump is turned off and then open all the taps a little to allow expansion should the water freeze in the pipes anywhere. When boarding I close all the taps and turn the pump back on and expect it to run for a short while to pressurise again. Only had one problem after a very prolonged cold spell which was with the water filter to the filter tap in the galley which had split. It was never used anyway as I couldn't get the old filter off and it bought forward the plan to remove it from the cold water plumbing. I would however go for a full Winterisation if I didn't have the tube heater. I live about 2hrs away from the boat and normally visit at least once every three weeks. I know my plan isn't perfect as the electric could trip, but with others around me spending a lot of time on their boats, I'm reasonably confident that if the marina power goes down it would soon be sorted.

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