Volvo MD2B cooling system protection

Hello

I have a seawater-cooled MD2B which runs nicely with no problems. I will have to be away from the boat for around 4 months and the engine will remain idle. It's not possible to have someone to run it occasionally because the boat is in a mooring. Also, I have a dynastarter, not strong enough to start the engine, so I am doing a combination of handcranking and dynastarter action.
I read the procedure in the service manual about winterizing but seems too complicated, also I don't want to touch the drain holes as the engine is old..

Is there a special antifreeze or other fluid I could circulate and let inside the cooling paths to prevent corrosion?
Thanks

For laying up, I run fresh water through my Bukh and then drain it. I do this by connecting the coolant pump to the galley water faucet so can be done on the mooring - so long as you've got enough water in the tank - about 5 gallons needed.

I really wouldn't worry about a sea water cooled engine on a boat on a mooring in the UK. I used to have an MD2B and kept the boat on moorings over winter several times. If the sea water around the boat isn't freezing then the sea water in the engine isn't likely to freeze either.

The sea water temperature in the UK drops to around 6C but gets no where near zero and with the boat on a mooring the interior of the boat is going to be roughly that of the surrounding water

I have an MD11C - same head and manifold, I agree with neil_s best to flush and drain. The drain taps on the head and manifold get choked with scale, but at some stage you want to get in there, remove the manifold and get all the scale and rust out. Rydlyme and flush. As long as you have good access the manifold comes off very easily. New drain taps are only £10, The reason being, people buy used MD2B complete engines just to get hold of the manifold, if that stops working, the engine is toast. At a minimum, flush with fresh water, even better leave something like Fernox F1 (for radiators) in the system, or just drain the seawater out and leave it dry.

Akestor said:

Hello

I have a seawater-cooled MD2B which runs nicely with no problems. I will have to be away from the boat for around 4 months and the engine will remain idle. It's not possible to have someone to run it occasionally because the boat is in a mooring. Also, I have a dynastarter, not strong enough to start the engine, so I am doing a combination of handcranking and dynastarter action.
I read the procedure in the service manual about winterizing but seems too complicated, also I don't want to touch the drain holes as the engine is old..

Is there a special antifreeze or other fluid I could circulate and let inside the cooling paths to prevent corrosion?
Thanks

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In your scenario you are not "winterizing" - just not running the engine for 4 months. The degree of corrosion will be exactly the same whether you run the engine or not. The winterizing routine is for boats that are taken out of the water which gives the opportunity to flush the system and leave dry for the winter period. It is of course worthwhile at some point to flush the system and clean out the water passages as it is the deposits that cause the long term issues of blockages and overheating.

In Athens, I wouldn't do anything, especially this time of year. A small solar panel to keep the battery charged might be a good idea but, apart from that, and making sure the boat's well ventilated and clean when you leave, I wouldn't worry about it.

Thank you for your replies

The service manual says: if the engine to remain idle for more than 14 days then internal corrosion starts. So I am running it every 2 weeks.
The good thing is that I disassembled the engine in 2018 and had the cooling paths cleaned.
Also around 2021, I circulated citric acid for descaling.
I am worried more about letting the same seawater ( without circulating for 4 months) but I guess running it with fresh water is the easiest thing to do.

My last boat had a raw water cooled VP2003. Based in the Solent, I never did anything special when leaving the boat, even in winter when afloat. The engine was around 15 years old when I fitted it, and it was still going strong when I sold the boat another 15 years later.

Does your engine have an anode? If so, I'd make sure it's got plenty of life left and not worry about corrosion. Like Tranona, I can't see why there would be any difference in corrosion rates between engine running and not. In fact, I could well imagine that a warm engine would corrode faster, as most chemical reactions go faster as the temperature increased. That's a big old lump of cast iron you've got there, it will corrode away eventually, but it's going to take a long time!

Reading the manual, I see the bit you mention. "If leaving the boat for more than one month, run the engine until fully warm every 14 days, and if leaving for more than a month, the engine should be inhibited" - oil drained and replaced with inhibiting oil, the fuel system faffed around with. I've two thoughts about that:

1. I doubt very much that even 1% of engines get that done to them, even when taken out of the water over winter, and aren't suffering as a result,
2. That sounds as though they're concerned about condensation inside the engine and fuel system. In Greece, in spring, with increasing temperatures, it seems very unlikely. I certainly wouldn't lose any sleep over it.

Stemar said:

2. That sounds as though they're concerned about condensation inside the engine and fuel system. In Greece, in spring, with increasing temperatures, it seems very unlikely. I certainly wouldn't lose any sleep over it

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That's a good point, never thought of this.

Stemar said:

Does your engine have an anode? If so, I'd make sure it's got plenty of life left and not worry about corrosion

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The engine is wired on the bulb hull anode, and propeller anode through the shaft coupling

Akestor said:

That's a good point, never thought of this.

The engine is wired on the bulb hull anode, and propeller anode through the shaft coupling

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A hull anode does not protect the engine. It is there to protect the prop. It is connected to the engine in order to make the electrical connection to the prop.
Engines may be protected by an interior anode fitted in the cooling water circuit, but the MD2B is not protected by an anode.

Akestor said:

Thank you for your replies

The service manual says: if the engine to remain idle for more than 14 days then internal corrosion starts. So I am running it every 2 weeks.
The good thing is that I disassembled the engine in 2018 and had the cooling paths cleaned.
Also around 2021, I circulated citric acid for descaling.
I am worried more about letting the same seawater ( without circulating for 4 months) but I guess running it with fresh water is the easiest thing to do.

Click to expand...

Des the service manual suggest disconnecting the wet exhaust?

VicS said:

Engines may be protected by an interior anode fitted in the cooling water circuit, but the MD2B is not protected by an anode.

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Good point. A small anode might replace the temperature sensor since it's not needed for the idle period.

Akestor said:

Good point. A small anode might replace the temperature sensor since it's not needed for the idle period.

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It is unlikely to do much good. You would need an anode in each cylinder head.