Raw water pump woes

[Leighb]

A minor further update. It so happens that for reasons best known to themselves the "first" engineers bought 2 sets of seals and bearings, and gave me the "spare" set for future use. I have brought them back from the boat and had a look at them. Having done a careful ball count it would appear that I have not lost any balls. That is a relief. The new bearings each have eight and there are eight remaining in the damaged races, what has at least partly disappeared are the cages that hold the balls apart So no balls have disappeared into the depths.
Also in answer to a query raised, the new bearings are in sealed plastic bags marked SKF 6203. The seals have markings MFC Tc 16 28.

Dragoon, there are definitely 2 seals, back to back between the impeller side of the shaft and the bearings. One presumably to keep the salt water out and the other to keep the oil in.

I have changed engineers, and as I said in my post I owe the other lot for their last lot of work, so deductions will be applied. There may of course be ructions.

A new pump has been obtained and is to be fitted on Monday, hopefully we may be operational again before too long.

 

[dragoon]

Sounds good. Make sure the garter spring on the seal is stainless steel - they last no time at all if they are mild steel (which most oil seals have). SKF bearings are good. Best of luck.

 

[Leighb]

More info

Below is a pic of the cam removed from the old pump. Not having examined one of these before I am not sure if it shows significant wear? Certainly to my eye the curve of the impeller face seems to have a groove in it where I would have expected an even arc in a new one?

The face plate certainly has obvious wear, if both these items were worn presumably that would degrade the output of the pump?

The raw water system has been treated with Rydlyme and a replacement brand new pump has now been fitted and tested - as far as we could moored in the marina. Running at 2000 rpm in gear for 30 mins the temp stayed steady at just below 80C, the turbo housing was at around 70C and the injection elbow at 37C which the engineer thought showed very satisfactory raw water circulation. It now remains to take her out to sea and try her at higher RPM for domestic and weather forecast reasons this can't be before Saturday, fingers crossed for a fine day.

 

[dragoon]

The cam is basic and just makes the impeller squash in and out. Unless excessively worn, I doubt as it will make a lot of difference. The face plate can be turned back to front, or you can make an inner plate from the lid of a plastic ice cream carton.

Good luck with trial. Hope all goes well.