Outboard winterisation in water

[Hangie]

Hi Everyone,

It might be a stupid question but I really can't google anything about it.

How to properly winterise an outboard engine on a boat which stays in water for a winter ?
On a trailer I would just trim it down and wait to self drain, but what to do if it does stay in water ? Is leaving it submerged as an outdrive is the only option ?

Thanks!

 

[Canopy Locked]

No stupid questions - you don't state location - I'm in highlands and used to leave my merry fisher (with outboard) in all year - never did anything special - don't leave the engine in the water - it'll get covered in crud and also there is the possibility of galvanic corrosion especially if there's shore power available. IMO it would have to get seriously cold before it caused problems

 

[Hangie]

I've sold my boat recently (outboard but on trailer) and looking exactly into something like Merry fisher 625/655 to keep in water in Solent area.
With 655 being shaft drive it is quite simple but 625 is an outboard and I was thinking what to do with the engine for winter.

It can get cold and windy on the coast so few degree under 0 is possible and if water will be left in a lower unit it could freeze.
On the other side leaving it in a water will end up with an extra unwanted layer on the paint and spring anodes change.

I was thinking about running the engine on a antifreeze solution but that would be quite challenging 1st to supply it to an engine and then catch water it will sputter to not pollute water.

Saying all that maybe it is just easier to buy 655/shaft if intention is to leave it in a water.

 

[Nito]

Out of curiosity, what would freeze?

Ignorant user here because I'm new, but...the engine is filled with oil and I imagine the leg has gearbox oil. Surely the water is brought in fresh when the engine is running, or do some outboards have a fresh water circuit also like an inboard?

In the event of seawater, shouldn't it be flushed out with fresh water to clear the salt using the ear muff things? Then couldn't you run it for a few seconds without any water to rid the system of any water therefore nothing left in there to freeze?

 

[Nito]

I've sold my boat recently (outboard but on trailer) and looking exactly into something like Merry fisher 625/655 to keep in water in Solent area.
With 655 being shaft drive it is quite simple but 625 is an outboard and I was thinking what to do with the engine for winter.

It can get cold and windy on the coast so few degree under 0 is possible and if water will be left in a lower unit it could freeze.
On the other side leaving it in a water will end up with an extra unwanted layer on the paint and spring anodes change.

I was thinking about running the engine on a antifreeze solution but that would be quite challenging 1st to supply it to an engine and then catch water it will sputter to not pollute water.

Saying all that maybe it is just easier to buy 655/shaft if intention is to leave it in a water.

You can get those rubber 'ear muffs' (sorry don't know the technical name) that go over the leg intake with a hose connection. There is also a feed cannister adapter you can get which can be filled with a desalt cleaning solution that you could use antifreeze with and catch what comes out of the outboard with a bucket or empty bottle but I can't see you'd need any water in there unless running dry for a few seconds would damage the water impeller?

 

[Hangie]

Engine (4 stroke) will have oil circulation, plus gearbox is also running in oil. Those wont freeze, at least not in the UK

Outboards got another circulation for cooling water. Intake is in lower units (where you connect muffs), then on top of it is water pump which pumps the water to power head, ECU and whatever else needs cooling. Then water is dispensed via telltale, exhaust and some pressure relief vales depended on the engine.

Point is outboard is designed to self drain when in a vertical position, so all the water from powerhead etc will be removed through an exhaust.
When boat is in the water, lowered engine will be underwater which means it will not drain fully and some water will remain. That left over could freeze. and blow something out. Questions is how to get rid of the water completely or replace it with antifreeze.

I assume if you could provide pressurised antifreeze through earmuffs and catch everything it would work. But it wouldn't be an easy job.

Running engine without water wont work and could damage water pump impeller very quickly as it will overheat - there is very tight fit there.. Why it wont work is very simple. When water pump impeller is not under water it will just rotate and heat, it wont create any pressure through the system to push the water out.

 

[Nito]

Can they not be left in water to self drain and simply raise them back up with engine off and in theory there would only be the water at the intake which would surely run straight out as it's still the lowest point and any water up in the head would have drained out by then?

I washed out the father in laws engines with muffs on while the boat was in the water the other day, connected it to a tap with an adapter that had some blue de salt solution. It's not the easiest thing to get the muffs on the outboard when it's raised and boat is in but I was able to hang out of the rear of the boat and get them on. Depends on boat, motor and arm length I guess

 

[Hangie]

Engine most probably wont drain while underwater. I've done very simple experiment. Take a pan full of water and a rubber hose. Put one end of hose in pan and fill out the hose with water. Hose is not draining if it is just over the water. It is due the pressure of water at the bottom of pan. In our case prop will be 20cm under water so those tiny amount of water in power head wont have enough potential energy to push though the pressure at the bottom.. For sure someone can calculate it but point is I doubt it will correctly drain.

Even if it would drain leg will be full of water. When you start rising engine water outlet very quick wont be lowest point anymore and some water will remain in a system.
Just to visualise:

https://www.galleonmarine.com/fckimages/IMG_0001.JPG

You can see how hight propeller is compared to the rest of the engine. Unless there is another water outlet I'm not aware off

 

[Nito]

Engine most probably wont drain while underwater. I've done very simple experiment. Take a pan full of water and a rubber hose. Put one end of hose in pan and fill out the hose with water. Hose is not draining if it is just over the water. It is due the pressure of water at the bottom of pan. In our case prop will be 20cm under water so those tiny amount of water in power head wont have enough potential energy to push though the pressure at the bottom.. For sure someone can calculate it but point is I doubt it will correctly drain.

Even if it would drain leg will be full of water. When you start rising engine water outlet very quick wont be lowest point anymore and some water will remain in a system.
Just to visualise:

https://www.galleonmarine.com/fckimages/IMG_0001.JPG

You can see how hight propeller is compared to the rest of the engine. Unless there is another water outlet I'm not aware off

That's a very good point, thank you!