Engine Flushing

[castaway]

This year I have started flushing thro my raw water system on my Perkins 4107 just before leaving the boat.

Any thoughts on whether this is worth while or are a couple of gallons of fresh water thro the system and the 5 mins or so it takes to do this just a waste of time?

Im considering a more permanant instalation with a "Y" tap in the inlet side to enable me to flush direct from the domestic water system, rather than what I do at present which is just disconecting the inlet pipe and pouring in fresh water from a container.

YVEA Nick

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[ccscott49]

If you are going to leave the boat afloat for winter, it might be OK, However if you are leaving it out of the water for winter, I reccomend you use a water/antifreeze mixture, as the water will probably freeze and you dont want that. If it's just for a few weeks, I wouldn't bother, I certainly dont. Just ensure your engine anode is in good condition. IMHO

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[chriscallender]

I think castaway's question was about doing this every time the boat is used, rather than just for winterising, since he wants to make a permanent connection to his domestic water system. I don't know if this would be a good idea to reduce corrosion - my gut instinct tells me there must be some problem with it otherwise everyone would do it but then again its good practice to flush outboards with freshwater every time they are run.

Obviously freezing is an issue in winter.

Chris

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[Roberto]

I would not connect the water intake directly to a pressurized fresh water system; much better use the Y-valve with a hose going into a bucket filled with fresh water

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[samwise]

I read it as a winter layup proposal, in which case he would have to make sure that he flushed the whole engine. In the case of my Bukh this involves taking a hose off the water pump into a bucket ( in fact a number of buckets) of fresh water and running the engine to flush it through. It needs to run long enough for the thermostat to open or you have to clamp off the pipe to ensure that all parts of the engine are flushed. My last bucketful contains an anti-freeze solution which I leave in the engine over winter on the basis that the solution contains corrosion inhibitors.

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[VicS]

I assume you are talking about a direct cooling system and not about flushing the raw water side of a heat exchanger. The problems are that it takes a lot of flushing to be really effective as much of the water bypases the engine and goes straight into the exhaust (all of it until the thermostat opens) and there will be areas which will be relatively stagnant. To be effective you really need to drain the system first to get rid of the salt water or at least open the drain valves while the flushing is in progress (taking care not to starve the exhaust cooling). To be certain that you have acheived adequate flushing you need to monitor the salt content of the water leaving the engine, fine if you have a chemistry laboratory on board.

Your profile indicates that you have a large family so perhaps here is an idea for an A level chemistry project for one of them.

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[castaway]

Just to clarify the question. It is the raw water side that I would be flushing. The theory is that as the boat spends most of its life sitting on its mooring even during the summer, it must be worthwhile flushing the seawater out of the heat exchanger. If this is done soon after the engine is shut down after the last use of a weekend, the thermostat is going to be open anyway.

My thought was just that, most ware /damage to engines happens due to lack of this sort of care, Sort of out of sight out of mind neglect.

All best Nick

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[VicS]

I'm still not clear if you are talking about a directly sea water cooled engine or an indirectly cooled engine. If the latter and you are talking about flushing the sea water side of the heat exchanger then that should be much easier to do effectively as all the water goes through it and there are no dead areas which will be difficult to flush. The reference to the thermostat is also irrelevant as this only controls the flow of fresh water (hopefully containing antifreeze) through the engine.

I think I would be guided by the evidence of corrosion, or not, in the heat exchanger as to whether or not it is worth doing.

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[castaway]

Hi Vic, Yes it IS the raw water side I am flushing. The engine side of course is sealed antifreeze/freshwater.

Trouble is that although all through the winter the raw water side is flushed and full of a/freeze, during the summer it happily pickling in seawater, I simply assume that if one sets up a simple flushing method for the raw water side it would help put of the day when the heat exchanger needs to be replaced...

By the way you're quite correct about the thermostat it is of course on the engine side...

All best Nick

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