Engine drain-down or use antifreeze/inhibitor??

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bluedragon

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Not sure what to do this winter. Boat will stay afloat. Not worried much about freezing-up (generally mild in Cardiff Bay), but would like to minimise corrosion in an old engine. I can quite easily drain-down, but I wondered if adding anti-freeze or some sort of corrosion protective solution to the engine block might give more protection than just leaving the coolant channels in the engine empty, but probably still wet for a few months? The bay is fresh water, so no seawater in the engine at present. Thoughts??
 
I would flush out the system and re fill with a new mix of water and antifreeze,corrosion is a lot worse with the system damp and full of air.
Pete
 
Those were my thoughts as well, although I seem to remember the previous owner flushing through with something before draining? Ordinary car anti-freeze is as good as anything I assume?
 
It is always advisable to have either antifreeze or a summer coolant additive in a fresh-water cooled engine (any sort, not just a boat). The additives are beneficial in inhibiting corrosion, reducing the possibility of cavitation and preventing sludging.
 
Inhibiting oil...

Some years ago, I had a seawater cooled Volvo. The procedure recommended by Volvo for winter lay-up involved running a 5% solution of inhibiting oil through the engine, then draining. As an alternative, you can run an antifreeze solution through and leave it in the engine - good antifreeze has corrosion inhibiting properties.
 
Would recommend keeping engine cooling full of water/anrifreeze solution, so that the engine can be started at any time if the vessel needs to be moved.
 
Ah!

Since its' not likely to freeze, I guess you could just do nothing.

In Scotland where it is likely to get quite cold I have taken the precaution of flushing through the sea water system with a water/antifreeze mix, and then reconnecting skin fitting.
 
Re: Inhibiting oil...

[ QUOTE ]
Some years ago, I had a seawater cooled Volvo. The procedure recommended by Volvo for winter lay-up involved running a 5% solution of inhibiting oil through the engine, then draining. As an alternative, you can run an antifreeze solution through and leave it in the engine - good antifreeze has corrosion inhibiting properties.

[/ QUOTE ]

I think the previous owner used this inhibiting oil solution, then drained down. Do you remember what the product was? I'll probably go the ant-freeze route, but in case I do drain-down it would be useful to know what would leave a protective layer in the engine.
 
Are you referring to

the raw-water system or the closed cooling system?

If yours is an indirect cooled engine, change the coolant every 3 years for new mix containing at least 20% and not more than 45% antifreeze. Don't empty it and leave.

For the raw water system run through with 5:1 freshwater/antifreeze mix, until you see coloured water coming out of the exhaust.
I always used to disconnect the inlet hose to the filter trap and put it in a bucket of antifreeze mix - you can do that in or out of the water.

Don't leave a system empty, it can have a bad effect on rubber parts like O-rings and impellers.
 
The problem...

with that method is that if you run such a solution through the engine from a container it will be cold. The thermostat will be closed and your solution will not go through the engine but simply around the bypass, however that is configured on your engine. Ideally you should circulate the solution around the engine until the thermostat opens. This can be done by catching the water expelled from the exhaust pipe in a container, a 5 gallon bottle with the top cut partly off is ideal, then taking the engine suction from the same container. Once the solution is hot you can shut the engine off and drain down. Hot in the context of raw-water cooled engines means over the thermostat opening temperature which is usually something like 60 - 65 C.
 
Re: The problem...

Thanks, but I don't think they'd invented thermostats when my engine was built /forums/images/graemlins/smile.gif. I'll have another look at the handbook however.
 
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