So, I had finished servicing the engine, (Buhk 10ME) filters, oil change etc. The last job was to clean
the raw water filter. Having done so, I started the engine and it fired up beautifully, but no cooling water
pumping through. OK I didn't put the filter back together properly, redo it....same result. Righto then what
else could it be. I took the inlet pipe off the water pump, opened the seacock and blew...I could hear the water
bubbling so no blockage. started the engine..no pumping. Reassembles and took the plate off the front of the
water pump, the impeller was perfect. Reassembles.. OK...Took the flexible outlet pipe off and started the
engine, no pumping. Took the plate off the water pump again and turned the engine over and the impeller
turns just like it's supposed to, reassembles and scratches my head...What the.....So i'm telling Missus
all about what I've done and how I'm stumped. She says 'it seems you've done everything, but have you? is
there just one thing you hav'nt done?'.
'Well', I says. 'The only thing I hav'nt done is change the impeller, but I've checked it and it's perfect'.
'Righto', says she, 'put a new one in'.
So I did, started the engine..Bingo...it pumped.
I had a real good look at the impeller and could see nothing wrong until I discovered I could peel the neoprene
away from the brass insert.
My impeller is neoprene with brass insert that has a pin going through it that locates in a slot in the pump
spindle. The noeprene had become detached from the brass. When I took the front off the pump and turned
the engine over the impeller would turn, but when assembled and the weight of water was on it the brass
insert would just rotate inside the neoprene.
Youse wouldn't read about it, would yer.

Yes MB. The impellers do a lot of work don't they. Fortunately I had a brand new one to
put in. I've just contacted Bukh at Tarren Point to send up another one...pronto.
I'm not keeping a used one as a spare.

Not sinking , but mine filled the engine up with sea water when the anti siphon valve packed it in. I now close the sea cock. Impellers are cheap and I keep a spare on board.

oldboyracer said..
Not sinking , but mine filled the engine up with sea water when the anti siphon valve packed it in. I now close the sea cock. Impellers are cheap and I keep a spare on board.

I have seen two boats develop leaks in cooling systems with the engine cock open. The bilge pumps stemmed the flow but not something I want to chance.
My cooling system has numerous rubber connections, you only need one to be a bit loose through vibration and a big wake to savage the boat and you just might be in trouble.
I always close all sea cocks when not on the boat and when not needed more than 10 miles offshore. If in doubt that you will forget it put the keys on the cock when it is closed.
Changing mine is a nasty job requiring removal of the heat exchanger. The manual says 400 hours and I have experience of impeller longevity now so 300 hours will do.
Except immediately after an impeller change when the pump is dry, the engine and pump are full of water. Forgetting the sea cock for a few seconds won't cause any damage. If it is run dry for more than say 20-30 seconds, or with the engine above idle, I replace it.

Ramona said..

Jode5 said..
I replace the impellers on my motor and generator every 100hrs or 12 months. Volvo certainly doesn't miss you when buying one for a 110hp motor. The other thing I also do is never leave the the engine seawater cock shut off. I have heard of so many people that have buggered pumps by forgetting to open the cock but never heard of a boat sinking because the cock was open. ( but I am sure someone has.) if an impeller has been run dry, get rid of it.

Close the valve and leave your engine key with a tag on it over the valve handle.

My new motor doesn't have a key!
I know I would forget to turn the cock on.

Forgetting to open the tap is like forgetting that you need to turn the key(or press a button) to start the motor
No key is hanging off a tap in my boat.

I agree with all of the above ...... impellers are the bane of my sailing life!