Lister STW inhibited raw water flow

[Linguistine]

Hi - direct cooled 20HP Lister STW, runs fine apart from lack of raw water flow so temp goes up.
Renewed exhausts, sea cock hose, I have a good flow of 'sea' pouring into boat from sea cock when open, had Jabsco pump out and checked runs ok so its a blockage after the pump - can see the hose feed into the elbow flow only dribbles out - ( thermostat checked and opens ) - noticed some gunk and a bit of general loose corrosion under the thermostat that I cleaned out. I've had an endescope in every part that I can get it into without seeing any significant or any blockage but obviously there's plenty of places for it to block up. Somebody suggested flushing water through from tap on pontoon via hose to see if it nudges whatever is blocking the system. I have never winterised it (three years in, but need to look into doing it!) as I live on it and the theory was to run it and go sailing more often. It was flushed with Rydlyme just over two years ago, however somebody told me that doing this can cause problems (?) and that the Cylinder head needs checking / cleaning out (no idea if I can do this) as is a common problem and no engineers working here currently for obvious reasons. Can I do any wrong by trying flushing water through it first? Any advise most welcome.

 

[Amlov]

Hi Linguistine
I guess the obvious is whether there is a problem with the impeller. I had one that the rubber essentially parted company with the stainless central shaft. With the cover off the impeller spun round when the engine started but the friction of the cover was enough to let the shaft spin within the rubber bit once the cover was put on.

Probably a reasonable first approach to check that the rubber part of the impeller is still firmly attached to the inserted shaft that provides the drive.

Andy

 

[vyv_cox]

I am not aware of any negative effects from using Rydlyme except that it attacks anodes. Flushing with fresh water will do no harm but may not do any good either. Draw water from a bucket, do not attach hose to the pump. I would try another go with Rydlyme if flushing is not effective. Follow their procedure.

 

[Linguistine]

I am not aware of any negative effects from using Rydlyme except that it attacks anodes. Flushing with fresh water will do no harm but may not do any good either. Draw water from a bucket, do not attach hose to the pump. I would try another go with Rydlyme if flushing is not effective. Follow their procedure.

A bucket of water to the pump doesn't suck water in. I was going to take the impeller out and attached the hose to the inlet of the pump? No good?

 

[Linguistine]

Hi Linguistine
I guess the obvious is whether there is a problem with the impeller. I had one that the rubber essentially parted company with the stainless central shaft. With the cover off the impeller spun round when the engine started but the friction of the cover was enough to let the shaft spin within the rubber bit once the cover was put on.

Probably a reasonable first approach to check that the rubber part of the impeller is still firmly attached to the inserted shaft that provides the drive.

Andy

Thanks - I've had a couple of new ones in and out now, unless its something simple like the Jabsco pump cover plate is on too tight! The pump was checked independently by a engineer but I tightened the plate slightly after I got it back...cant be that surely... ?