Water Pump Impeller looks fine but..??

[SAWDOC]

You say that you were in rough conditions.

My bet is that air was getting in when your back end lifted so reducing the amount of water round the system and causing the engine to overheat.

I agree. However accepting Vyv's point that the pump should be self priming why did the engine again overheat as I ran back to the mooring? And then not overheat after the inspection of the raw water intake as described in my earlier post?

 

[LadyInBed]

why did the engine again overheat as I ran back to the mooring?

Because it was very hot to start with?

And then not overheat after the inspection of the raw water intake as described in my earlier post?

Because it had cooled down by then?

 

[vyv_cox]

From what you say,is it possible that your water filter(or its piping )is mounted too high above the outside water level and needs to be lowered to match that level when static.

The strainer must be mounted above water level, any lower and there is a risk of flooding the boat. Vetus say a minimum of 150 mm (6 inches) above the water line. See here

 

[SAWDOC]

Sorry guys,
spent the last twenty minutes typing out a lengthy feedback response to this only to get dumped out before i could hit the submit button so here's the essentials - not going to spend another 20 mins on this

Cover plate was worn - got a new cover plus the tip "next time just reverse your old cover" for €10 which I thought was ok.

Cleaned out pump housing with acetone. Improvement but not 100% successful at removing black deposits.

Raised the inlet raw water strainer slightly (say 25 mm or so) prompted by Vyv's comment above - this may have had the accidental effect of giving the inlet hose a better hydraulic profile (less kink)

Ordered new impeller but while waiting decided to insert old but good impeller.
Hey presto - large flow of water through transom , less when i increased revs out of gear but no overheating.
Henceforward pump housing will be inspected as least as much as impeller during annual inspection.

 

[kieronriley]

pump face worn

if your pump face was worn then you must have had the engine for quite some years ,so the next thing that you will have to watch is the small bronze cam inside the pump i should think this maybee showing signs of wear,and you will get the same sort of symptoms when or if itm does wear,your engine at tickover will pump water but when running at speed will not pump enough water to cool engine,a quick fix to get you home is to take the cam out (one screw in the middle)and put a thin packer in behind it then refit and this will work for long enough to get and fit a new cam. Kieron

 

[vyv_cox]

if your pump face was worn then you must have had the engine for quite some years ,

Not always true. Sandy and silty water will cause wear quite quickly. I wore a circular scar almost 1 mm deep in 11 days transiting the Canal du Midi.

 

[tudorsailor]

Easier changing of impeller

Just as an Aside, I have a Yanmar and I got this cover which makes changing the impeller really easy. If I ever have to do this at sea, I am confident that the speedseal will make it very easy

No commercial connection

TudorSailor