Yanmar 4JH3E impeller

Yesterday I changed the impeller on our engine ,when the old one came out of the housing there were only three veins left from the original twelve.
Has this happened to anyone else if so do they know what caused the damage?
Secondly does anyone have any ideas at which end of the heat exchanger I should try and retrieve the disconnected Veins?

Robbo wrote: Yesterday I changed the impeller on our engine ,when the old one came out of the housing there were only three veins left from the original twelve.
Has this happened to anyone else if so do they know what caused the damage?
Secondly does anyone have any ideas at which end of the heat exchanger I should try and retrieve the disconnected Veins?

I would pull the hose off the forward part of the heat exchanger. But I had I have an IP 31 and yours may be different. Would not hurt to pull the hose and take a look. Of course sometimes the hose will not come off. Then you have a challenge. You have to decide whether not to cut it off or let it be. But the time is now. No need in letting it wait until there is a problem.

Thanks gentleman.
On Monday I started taking things apart and found that bi have an oil cooler.The raw water goes through the oil cooler before if gets to the heat exchanger,at the in end of the oil cooler i found three veins of the impeller and a grill that the other veins were unlikely to go through.Then i removed the pipes from the end of the heat exchanger,nothing there.
Having spoken to an engine man who suggested that the remaining impeller ends must have disintegrated i have put it all back together and intend to service the exchanger during the coming winter.

Tony