Seawater intake blockage

[Tranona]

One solution, but not always possible is to locate the water strainer above the waterline and immediately above the inlet seacock, preferably a straight through ball valve. Then you can rod any blockages straight down. I was able to do this on the last engine installation I carried out, but unfortunately on the one I am about to do it is not possible.

 

[Moodysailor]

One solution, but not always possible is to locate the water strainer above the waterline and immediately above the inlet seacock, preferably a straight through ball valve. Then you can rod any blockages straight down. I was able to do this on the last engine installation I carried out, but unfortunately on the one I am about to do it is not possible.

Having the stariner above the W/L is great advice for many reasons, not least the one you mention.

On one boat I worked on the manual bilge pump was nearby the engine compartment and had a wandering hose that could be dropped over the side. The owner had made a small fitting that would plug the inlet stub of the strainer then all he needed to do was pump the bilge pump handle a few times to blow out any blockage. He used to do it a few times a season just to keep any growth out of his inlet.

Earlier posts talked about external grates/cover for the seacock. I advise against these unless they are the type that can be easily removed for cleaning - a scoop is needed on a high speed vessel for positive pressure, but is not necessary on a sailing boat as it doesn't move fast enough for any benefit. The grates/covers are intended to keep large debris out, but in practice they foul up or get blocked with antifoul more often than not which leads to issues down the road. Common practice on yachts now is to have an open seacock and let the strainer take care of any debris.

 

[Neeves]

Jonathan,

You will note that during your absence the ideas dried up. Once you re-appeared the thread has redeveloped - its amazing how the absence of an OP leads to an absence in interest in (we) helping them.

Unless its an anchor thread and then they have a life of their own.

Saildrives offer a difficult installation. Foulings can get into the inside of the sail drive, where, living a sheltered life, that can grow. If you ream the sail drive out the debris might be bigger than the vent holes and bigger than the water inlet in the sail drive housing. I don't see how the debris can be removed and not block the ball valve.

I don't have an answer - but I do spend a lot of time with dowel, from the engine side and screw drivers ensuring I get all the shell pulverised and out - but I'm never sure its perfect.

I've never had the courage to pour acid down the insides - from the engine side - nor leave the ssaildrive sitting in a bucket of weak acid.

Take care, stay safe

Jonathan

 

[Aeolus]

Saildrives offer a difficult installation. Foulings can get into the inside of the sail drive, where, living a sheltered life, that can grow. If you ream the sail drive out the debris might be bigger than the vent holes and bigger than the water inlet in the sail drive housing. I don't see how the debris can be removed and not block the ball valve.

It's not a saildrive, this is the seawater intake for the engine and it's via a unprotected thru-hull.

To my mind, since blockages can't be prevented (even if their frequency can perhaps be reduced) the solution is (a) early detection and (b) quick method of clearing. I've ordered the Aqualarm suggested in this thread (thanks guys) and am working on a quick method of clearance.

At the moment I have to detach the incoming hose from the water-line level filter and then I blow down that - it works but requires fiddling with a jubilee clip and then reattaching the hose so not very quick. Maybe some form of garden hose-type attachment before the filter that can easily be separated, else something that I can insert into the in-pipe inside the filter that would give a good enough seal that I could then blow into it.

Ideally I would detect the blockage and clear it without having to turn off the engine.