Filter for sea-water engine coolant?

[Sinbad2222]

My boat doesn't have a filter adjacent to the sea water seacock. Is a filter essential and any recommendations for the best make to fit?

 

[Poignard]

You need a filter somewhere between the sea-cock and the cooling water pump to prevent the cooling system becoming blocked by weed and debris, which could result in a wrecked engine. There are various types [see www.asap-supplies.co.uk]. I have a Blakes seacock, which has a coarse strainer plate outside the hull, and a Vetus filter mounted next to the engine where it is very accessible and I can see at a glance if it needs cleaning out. This works very well.

 

[angelsson]

A raw water filter is essential as already explained.
I have a filter fitted at the seacock, inside the body of it is a stainless mesh circular filter about 5 inch tall and 2 inch diameter, access is easy from the top to either remove for cleaning or if in a hurry turn it around to present an unfowled area of the filter to the input from the seacock. I remove and clean after approx 200 miles, not had to replace it yet.

 

[cindersailor]

I can recommend the plastic filters sold by ASAP (prod code 402194 for 3/4" hose). I was a bit dubious of the quality given the very reasonable price (cf. Vetus), but was rather impressed when it arrived. You will need to buy the plastic hose tails too, but those too are cheap. Mount it just above the waterline so that you can take the lid off to clean without closing the seacock.

 

[Flossdog]

My Southerly 115 had a poor arrangement with a brass tube type "filter" attached directly to the ball valve. It was not easily accessible and when it blocked on the outside strainer I decided to update it. I took off the outside strainer because when it blocked (often in Milford Haven which is very weedy), it was not possible to clear it without going under the boat. So I bought a Vetus strainer which seems to work very well. I sited it so that the top is just above water level and on the centre line of the boat. I also sited it under the companion way steps outside of the engine compartment. This way I can see when there is a lot of weed in the strainer and remove it before trouble is caused. The system seems to work well.

 

[Amari]

I wonder if sea water filters are a relatively recent developement. My 1985 Wauquiez (Volvo 2003) which circumnavigated with previous owner did not have one. I have now fitted a Vetus filter, and by the by upgraded to volvo MD40

 

[Topcat47]

No not that recent, my Nic is over 40 years old and has a strainer fitted. It was old when I bought my boat and has never been replaced, although removig, cleaning and replacing it is getting a bit of chore as the plastic from which it is made has hardened over the years.

 

[DaveS]

I think it varies. My 1989 boat didn't have a strainer when I bought her, however the water is drawn via a saildrive which has a series of holes that must act as a very course filter. Outboard motors seem to work OK like this.

However I fitted a Vetus strainer which has worked reasonably well, but I did spot two points. 1. Quite a lot of vasaline or silicone grease is needed on the big O ring and the cap threads to both make a good seal and allow the lid to be removed at all easily. 2. The plastic body gets quite brittle at low temperatures. In trying to get a hose to come off I broke off one of the spigots: much bad language. I fixed it using a piece of copper pipe as an insert and quite a lot of epoxy. I also now have a tee piece, valves, and a length of hoze permanently fitted so that without removing hozes the suction can be diverted to a bucket for winterising (or, potentially, the bilge in an emergency).

 

[thalassa]

In my old boat, I had the plastic Vetus type with butterfly nut, and it was rubbish. Eiither had a vacuum leak in the center seal, or the large O-ring would flatten after a year. Replaced it by a brass tube type, which takes standard flat O-rings from the DIY. Present boat has the larger Vetus type, which is far better (no central nut), but had to replace it too, as the clear plastic had cracked.
Just the other day, I had a Dutch friend visiting, who told me he had the insurance surveyor round to have a look at the 35 ft sailboat he finished from casco upwards. The surveyor wouldn't guarantee the engine unless he changed the plastic Vetus strainer for a brass one! Apparently, they had to pay out for several engines overheating through a failing plastic filter...

 

[DaveS]

Er, thanks for that! Now there's another thing to worry about. /forums/images/graemlins/frown.gif

 

[Sinbad2222]

Thanks for all the advice and opinions - my prority job now is to fit a strainer!