Habebty
Well-Known Member
Just had to change my impellor in a lumpy chop off Newhaven. It was new 2 weeks ago. Anyone else had a new one lose half its vanes. Any likely causes?
New Impellor Disintegration
- Thread starter Habebty
- Start date
Daydream believer
Well-Known Member
I had an alarming amount fail in my first 2-3 years of my new boat. One in a difficult situation. Then I went back to buying the only slightly more expensive Volvo ones & they last about 4-500 hours. I do take them out over winter so that one side of the vanes are not compressed.
I think it helps to make sure that it is put in with the rotation the correct way round to avoid kinking the vane on a dry startup. In fact dry running is always the biggest killer, so perhaps you had restricted flow for a while without knowing.
I think it helps to make sure that it is put in with the rotation the correct way round to avoid kinking the vane on a dry startup. In fact dry running is always the biggest killer, so perhaps you had restricted flow for a while without knowing.
greeny
Well-Known Member
Was it OEM or a copy part maybe from china?
Habebty
Well-Known Member
OEM, no idea how long it had been on the shelf though. I suspect Daydream’s explanation of unknown dry running or low flow is a strong possibility?
Spirit (of Glenans)
Well-Known Member
Everything is from China.
Spirit (of Glenans)
Well-Known Member
Volvo Penta do not manufacture the pumps. They fit pumps bought in from specialist pump manufacturers, mainly Johnson. Most owners fit Jonhson impellers rather than ones bearing the VP brand, which are more expensive. My guess is that your VP item was sitting on a chandelry shelf for years.
Moodysailor
Well-Known Member
If the impeller failed, it is because it ran dry, or perished. As you have said it's fairly new, we can rule out the latter, so the former is the source. The root-cause may have been the lumpy sea allowing air to be drawn in, or an air leak from another area (i.e strainer).
Contrary to some belief, it is very rare for an impeller to fail due to a restriction or blockage after the pump. If there is water round the impeller it will be lubricated, and it is this (or lack of) that destroys impellers in short time, not a lack of flow.
Contrary to some belief, it is very rare for an impeller to fail due to a restriction or blockage after the pump. If there is water round the impeller it will be lubricated, and it is this (or lack of) that destroys impellers in short time, not a lack of flow.
Plum
Well-Known Member
If you look at the tips of the failed impeller vanes you should see signes of friction-heat damage that would have precede the loss of the vanes due to insufficient water lubrication. If there is no such tip damage then sub-standard material could cause vane material fatigue.
I removed an impeller 2 years ago while doing some other work on the engine and discovered a long crack at the base of one vane. Luckily the vane had not quite detached, it had been in use for 50hours. There was no damage to the vane tips. ASAP Supplies, who supplied the Orbitrade impeller, immediately sent me a replacement. The replacement is still good after 150hours.
Www.solocoastalsailing.co.uk
Jim@sea
Well-Known Member
Some impellers can be on the shelf in a Chandlers for years before they sell them. Just like Cam Belts where once fitted they are supposed to have a lif of 3 years before being replaced, but how long were they on the shelf before being sold.
Daydream believer
Well-Known Member
That is a bit like "How long is a piece of string". Surely the guiding factor is engine hours & stating 3 years is a pointless statement- apart from deterioration from lack of use. 300 hours in one year against 30 in 3. There are lots who do not even do 30 hours.
Rappey
Well-Known Member
They can be rubber, neoprene ,epdm, nitrile etc. I can only think that people who get through one in a short space of time are not fitting the right type to begin with ?
My jabsco impellor is now 39 years old and still in great condition.
My jabsco impellor is now 39 years old and still in great condition.
Habebty
Well-Known Member
TBH, this is first one in 20 years that I have had fail. It was a new Johnson 6 blade impellor. There was no sign of friction damage, 3 vanes missing one recovered, the other 3 vanes were hanging off. put one of my old ones back in and lasted for a 4 hour motor from the Looe Channel to Gosport. Will pick up a few new spares tomorrow.
ChromeDome
Well-Known Member
When you buy an impeller kit there is a pouch in the box, marked 'Impeller lube', meant to be used when fitting the impeller into the pump housing.
It's really nothing too special (glycerine) and in this case 'any lube is better than no lube at all'. Dishwashing liquid, thin oil, mayonnaise... A little will do and will prevent dry running until water get's in.
It's really nothing too special (glycerine) and in this case 'any lube is better than no lube at all'. Dishwashing liquid, thin oil, mayonnaise... A little will do and will prevent dry running until water get's in.
Beneteau381
Well-Known Member
I experimented with the impellor the wrong way around with the cover off, within a turn it had righted itself, its not an issue. The other thing is that I was given a tip, take the impellor out over winter, clean the lip seal with nice soft cloth, then slather it with blue volvo grease. the grease keeps the seal in top condition. Also once run, there is enough water in the pump to stop it running dry for a few secs. Think about the Speedseal, his famous brag, used by the military and rnli so that the pump can be run dry. This is because the end runs on teflon. the vanes dont though!
Plum
Well-Known Member
Yes, agree, putting it in the wrong way is not an issue. In fact, when you next remove the pump cover you will occationally find the vanes pointing the wrong way. This happens when in the final second as the engine comes to a stop the compression of a cylinder can force the piston back down a bit to reversing the crank rotation sufficiently to reverse the impeller vanes. They revert to the correct rotation next time you start.
Www.solocoastalsailing.co.uk
david_bagshaw
Well-Known Member
did you recover all the vanes off the failed one?
they float back down the pipe when the engine is turned off, as the water in the sea water system returns to waterline level, some times a loose vane lands in the pump, next start the damage is done, stretch and tear.. A wet vac is useful to get the old vanes out of the plumbing...
they float back down the pipe when the engine is turned off, as the water in the sea water system returns to waterline level, some times a loose vane lands in the pump, next start the damage is done, stretch and tear.. A wet vac is useful to get the old vanes out of the plumbing...
Moodysailor
Well-Known Member
This is not strictly true. Rubber based impellers should not be fitted with an petroleum based lubricant (hence glycerin is included) as these can cause the rubber to soften, swell and fail. Nitrile impellers are resistant to oils so are OK.
Dishwashing liquid would be OK provided it isn't allowed to dry out before the engine is started. Your guiding principle of "anything is better than nothing" is spot-on though, so in a pinch anything will have to do.
ChromeDome
Well-Known Member
In all cases I can think of the engine was started to check the function immediately after fitting the impeller.
So while rubber and nitrile have different properties, a few minutes won't kill any in this connection.
Technically speaking you are right, however.
So while rubber and nitrile have different properties, a few minutes won't kill any in this connection.
Technically speaking you are right, however.
