Log in
Article search:

Q & A

Skin tanks

How do I flush out my skin tank?

Asked by: Dave & Ann Mackintosh  | 11.25am, Monday 31 October


WW says:

Good that you are thnking of doing this- a lot of boat owners don't- and if you have topped up with tap water (as well as antifreeze) you can get quite a lot of deposits which can hinder effective cooling!
Firstly, when draining the coolant, try to avoid pumping any of it overboard- the contents are usually quite toxic to aquatic life! However, this is not always easy.
Removing the return hose (the lower hose) from the skin tank- but detaching at the engine end, may allow you to collect the fluid in a bucket.
Remove the coolant output hose from the engine (which goes into the top of the skin tank) and run fresh water from a hosepipe into this, until water fairly free of antifreeze comes into the bucket.
You might then want to flush all the hoses, including the ones to a calorifier and gearbox oil cooler, if fitted, before refitting the hoses, and checking the jubillee clips that hold them. It is also a good time to check the condition of hoses, as they often collapse internally, while looking fine on the outside.
If you find lots of sediment, it might be worth refilling the engine with fresh water, running it up to temperature, and adding a flushing agent (radiator flush, from a car garage), to help remove any remaining material- though you will then have to drain and fully flush out all the pipework again.
When filling, if you choose pre-mix antifreeze, this is very useful, as it is made with distilled or deionised water, so reduced scale build-up. If you mix your own, then ensure it is mixed before adding to the engine. Then run the engine, and bleed off air bubbles from the calorifier pipework and the skin tank bleed screw.
Hope that helps!

Mark Langley  | 11.56AM, Monday 31 October


Readers say:

Thanks for that... Hopefully I'll get it done before the really cold weather gets here.

Dave & Ann Mackintosh  | 1.21PM, Monday 31 October

You must log in to post an answer.