Tips on how to winterise a Mercruiser 5.0L in the water

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peterscollins

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I plan to keep my Bayliner 2865 in the Thames this year - she was out of the water in the summer and had a pretty full service before we bought her.
So, how do I fill up the engine and sterndrive cooling water systems with anti-freeze, because it won't be easy to suck up the anti-freeze, as shown in all of the videos that I've seen, which show how you do it with the boat out of the water.
 
Assume your engine is raw water cooled?

Anti freeze (off the shelf stuff anyway) is poisonous so I don't think its a good idea to be pumping that through the engine block and into the river..

Your best bet would probably be to keep the engine bay heated to say 10C which would stop the damp and mould but would also stop the water in the engine block from freezing..
 
If you are in a marina and have shore power a tube heater in the engine bay is the usual procedure. You may wish to place insulation over the engine.
I recently purchased a temperature controller from B&Q which I have set to switch on the heater if the temperature falls to 5 degrees.
 
Pretty dangerous advice in my opinion.
Heaters are good as an extra and to keep damp and corrosion at bay, but not as a replacement to winterising.
Many hundreds of boaters each year will testify to this. All it takes is a power cut or a breaker trip (gone unnoticed) on your supply box and its game over !
Follow the manual. Most engines can be winterised in the water.
If it's a gm based 3.0 4.3 5.0 5.7 mercruiser, omc or Volvo penta... it couldn't be simpler to do. Most diesel Volvo penta are easy too.
Many people have their own variation in how to do this but the theme and fundamentals remain the same.
Drain all raw water areas and perhaps even flush or fill with antifreeze.
All the best
 
With the 5.0 Merc, the filling will work;
If it's a carb with drain plugs;
Remove a plug each side (down below spark plug level and will either be a brass or blue plastic plug) watch water drain then poke a wire or small screw driver in there and make sure no junk is stopping water egress
Remove plugs on each exhaust manifold (usually at the back near cow horns) will be either a big brass plug (22mm spanner fits some) or blue plugs
Remove all hoses from thermostat on front of engine, then hold down as low as possible into bilge to drain.
If you have a hot water system off the engine, remove these two hoses and blow through one end to ensure water comes out other hose.
Now either replace all hoses and plugs or fill with antifreeze 50/50 mix (if you want specifics about this method let me know) then replace all hoses and plugs.
There is sometime a variant in the plugs, depending on the age. Some have all blue obvious butterfly plugs and some have a mix. The block drains (down side under spark plugs) are the most crucial.

If you have a 5.0 efi or MPI
These tend to have a single point drain method and are know to occasionally fail to empty all the water out after a few years of gunk and corrosion build up in the drain channels. You will need to fill or flush with antifreeze if you have this engine.

Because your boat is in the water, you will not be able to completely rid your engine systems of water, because some of the system will be beneath the water level of your boat. The intake hose from the leg to the thermostat (and perhaps power steering cooler) will still have water in them. Don't worry too much about this. The general idea is that the temperature of the water your boat is sitting in, will be the temperature of the water in this hose. This is because they are directly connected in a conductive sense.
Generally SW or flowing water doesn't freeze in these parts.
All the best
PS, the above has worked in the Scottish winters for the last 20 years of ownership, with regards to these specific engines.
Most recent engine I own is the 5.0 MPI.
Currently winterised as above and also filled with antifreeze (out water)
 
Many thanks. There are 2 tube heaters down in the engine bay with a thermostat fitted, so I need to make sure that they are working. I think that I will also try to follow the advice below on winterizing with non-toxic anti-freeze.
 
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