Volvo Impeller Disintegration - Lost pieces

[blueb]

As a result of dry running for three minutes the impeller on my Volvo Penta 120SE has shed one complete blade and pieces off two others. Does anyone have experience of this happening and have any ideas as to where they are most likely resting now after several hours running time? I would like to not have to dismantle the whole sea water cooling system.

 

[Stork_III]

When it happened on my MD2020, the bits were to be found in the rubber bellows just before the heat exchanger.

 

[davidej]

Should one find these?

We had an impellor lose several lobes early last season and just put a new one in without looking for the pieces.

Are we in danger of getting a blockage ? I blithely assumed they would be washed thru the exhaust eventually. It is a VP2030

 

[LittleShip]

As a result of dry running for three minutes the impeller on my Volvo Penta 120SE has shed one complete blade and pieces off two others. Does anyone have experience of this happening and have any ideas as to where they are most likely resting now after several hours running time? I would like to not have to dismantle the whole sea water cooling system.

Heat exchangers normally have some type of a tube stack that the cooling water runs through. It is most likely that the pieces of the impeller are at the inlet end of the stack. Failing to remove them can cause the engine to over heat due to lack of water flow.

As an aside, on trawler yachts it is quite common to fit two strainers to the cooling system, one on the inlet to the pump and one on the outlet so that any debris from a damaged impeller gets caught in the outlet stainer and will not cause any further problems.

Tom

 

[Monique]

When it happened on my MD2020, the bits were to be found in the rubber bellows just before the heat exchanger.

Yes. Same for me... luckily, it is easy to change.

Always carry a spare

 

[samwise]

It would be interesting to know if there is a benchmark for the life of an impeller. I have always replaced the impeller at the start of each season -- a routine procedure that also includes the primary fuel filter ( oil filter done at the end of the season with oil change). However one hears of owners who run impellers for some years without problems.Even Pat Manley the PBO engine guru, admitted to failing to heed his own advice when an impeller on his boat failed and he realised it had not been changed for a few years.
I suppose that if you remove the impeller at the end of the season to avoid the vanes taking a set, check it over carefully for signs of splits etc and then lubricate it properly when replacing it at fitting out time, it ought to do you for at least a couple of seasons ( average use). But I have to admit that I would feel a little uneasy about it and will continue with my current practice of fitting new each time. Of course I do have an impressive collection of "single season" impellers filling up my spares locker.

 

[shaunksb]

We had an impellor lose several lobes early last season and just put a new one in without looking for the pieces.

Are we in danger of getting a blockage ? I blithely assumed they would be washed thru the exhaust eventually.

I did a similar thing when we first had our boat in 2006. Noticed we were losing a little fluid through the expansion pipe on longer trips under engine so decided to wash out heat exchanger last year. Sure enough all the lost bits were still there - to big to flow through the small pipes of the heat exchanger.

Also we lost a complete lobe off the old impellor two seasons ago and last seasons had a split almost through another.

So I would always change the impellor on this engine every year and clean out the heat exchanger as soon as possible if i'd lost any bits.

We leave the impellor in all year and do about 60-80 engine hours a season on a volvo MD2030.

 

[neale]

It would be interesting to know if there is a benchmark for the life of an impeller. I have always replaced the impeller at the start of each season -- a routine procedure that also includes the primary fuel filter ( oil filter done at the end of the season with oil change). However one hears of owners who run impellers for some years without problems.Even Pat Manley the PBO engine guru, admitted to failing to heed his own advice when an impeller on his boat failed and he realised it had not been changed for a few years.
I suppose that if you remove the impeller at the end of the season to avoid the vanes taking a set, check it over carefully for signs of splits etc and then lubricate it properly when replacing it at fitting out time, it ought to do you for at least a couple of seasons ( average use). But I have to admit that I would feel a little uneasy about it and will continue with my current practice of fitting new each time. Of course I do have an impressive collection of "single season" impellers filling up my spares locker.

I guess it all depends just how easy your impeller is to change out at sea. I have a speedseal on mine with good access and I can change it easily in a minute or two. This makes me less inclined to stick to the every year schedule and in fact the current impeller has done four seasons. I checked it at the start of last season and it was fine so it went back in. I will probably change it at the start of this season as I think I have got my moneys worth! If it still looks good it will go in the spares locker as an emergency replacement.

The thing is, an impeller is most likely to let you down due to a blockage and a lack of cooling water. In this case it makes very little difference if you change the impeller every year or every four years it's still gonna be knackered and leave you in a situation where you have to change it at sea.

 

[EdWingfield]

As a result of dry running for three minutes the impeller on my Volvo Penta 120SE has shed one complete blade and pieces off two others. Does anyone have experience of this happening and have any ideas as to where they are most likely resting now after several hours running time? I would like to not have to dismantle the whole sea water cooling system.

I was advised by a marine engineer that I absolutely must recover every missing piece.

The first place to look is the end of the heat exchanger tube cluster nearest the impeller.

ps. with luck it's dead simple, undo two jubilee clips pull the hose gently back and you'll find the blighters.

 

[Heckler]

Should one find these?

We had an impellor lose several lobes early last season and just put a new one in without looking for the pieces.

Are we in danger of getting a blockage ? I blithely assumed they would be washed thru the exhaust eventually. It is a VP2030

As the OP said, the bits will be in the bellows against the face of the heat exchanger, big pieces lodge there, small pieces MIGHT go thru to the exhaust and out. You should always check when you find a damaged impellor!!
Stu

 

[pmyatt]

As a result of dry running for three minutes the impeller on my Volvo Penta 120SE has shed one complete blade and pieces off two others. Does anyone have experience of this happening and have any ideas as to where they are most likely resting now after several hours running time? I would like to not have to dismantle the whole sea water cooling system.

Any debris will end up at the heat exchanger. Disconnect the hose of the heat exchanger input and output. Connect the heat exchanger input to a hose over the side. Connect mains water to heat exchanger output and reverse flush - any debris should end up over the side.

 

[westernman]

It would be interesting to know if there is a benchmark for the life of an impeller. .

The servicing schedule for my Yanmar says change the impeller every 600 hours.

That will be in 8 years time at the rate we use the amount we use engine. I don't think I will wait that long.

 

[TonyS]

When it happened on my MD2020, the bits were to be found in the rubber bellows just before the heat exchanger.

It is possible to remove them by loosening the small fitting on the bellows and pulling it out and then using a pair of long nose pliers. You can generally feel the bits with a finger. The other place they sometimes jamb is in the pump outlet port, which severely reduces the flow.

If the pump runs dry the water seal also runs dry and will also fail prematurely.

Both problems can be avoided by fitting a spring loaded SS 3/4" non return valve between the pump and the anti syphon valve. The impeller and seal should then both last a very long time.