On Borrowed Time.

[Smoggy]

Just a little reminder for folks to check impellors for the new season, I recon I got my money's worth out of this one.

Only pulled the pump due to a leaking seal, next visit must change the other side one too, I think this one has been in since pre-covid so certainly due.

The white residue is not salt crust it's the developer spray I used to track the water leak as I thought it may be the inlet pipe o ring.

[BroadAmbition]

Wow, that was close.

I change ours at every major engine service at 750 x Hrs whether it is showing signs of wear or not and always have a brand new spare kept onboard

Griff

[Smoggy]

If anyone needs a spare volvo impellor they can have this one cheap, only one owner from new...

I'm thinking I may have done the other side more recently as I had issues getting it to prime and put it down to body wear so machined the base out to take a jabsco wear plate at the back along with a new cover, this one is still un-machined so I probably forgot to change it, oops! 

[Vaughan]

At least all the bits are still there and have not found their way down the pipes into the heat exchanger.

This damage could be caused by two things :

1/. Leaving the impeller in the pump over winter, which allows the vanes which are bent over the cam to get brittle and snap off.

2/. Which I think more likely - there is a constriction further down the system which means the pump cannot pump the water clearly away, so a back pressure is caused and this snaps the vanes off, as they "don't know which way to bend". The first place to look for this would be in the water injection bend, where the cooling water joins the exhaust. 

[Smoggy]

Nah it's old age and neglect on my part Vaughan, I never remove for winter as I don't lay up as such just chuck some freezeban down the strainers when I leave it if the weather is likely to get proper cold and leave the taps open, it may have only been changed once since I bought the boat in 2015.

This winter has seen the longest stretches of non use (a month at one point) due to swmbo having problems following an accident and me having a double hernia op early december but still no layup, the impellors were in place through the lockdowns too.

[Vaughan]

All the same, when the vanes snap off like that, there is a reason for it.  Normally it is back pressure in the pipes due to a constriction, which may also be a blockage in the tube stack of the gearbox oil cooler.

If the pump has been run dry, the vanes would be burned on the ends and there would be wear on the front and back plates.

I suggest you have a good look through the system, or the same problem may happen again.

[Cal]

We fitted the Speedseal front plates to the VP pump on our KAD32. It saved many an impellor when we had a restriction in the raw water flow.

Well worth the money. Also made changing the impellors much quicker.