fresh water impeller

[RoyS]

You should have strainers ahead of your raw water intake to prevent foreign objects from being ingested by the pump. I have a thruhull strainer on the exterior of the hull to keep jellyfish from completely blocking the intake hose and I have an inboard strainer to catch eel grass before it reaches the pump. I also keep a complete spare pump for quick changeout at sea if ever needed.

 

[splax]

reading replies there seems to be some confusion, or maybe it is just me...
: raw water impeller takes outside water through the heat exchanger to cool the fresh water-antifreeze mixture, which in turn cools the engine, this is rubber and wears, needs replacement on a regular basis

 

[jssailem]

raw water impeller takes outside water........this is rubber and wears, needs replacement on a regular basis

Yes.

The HeatExchanger has both the outside raw water in one path, and a second path for coolant mix. The coolant mix circulates through the engine carrying engine heat to the HeatExchanger. There the heat is transferred to the other loop of water. The raw water being sucked in, passed through the HE and then sprayed into the exhaust elbow and back outside to the sea, lake, or pond you are in.

 

[lehighsail]

Yanmar suggested taking out the impeller after winterizing the engine and sealing it in a bag with glycerin. Prevents it from taking the shape of the pump and becoming brittle from the AF as others have said here.

 

[jssailem]

Yanmar suggested taking out the impeller after winterizing the engine

Sounds like an interesting idea for a boat on the hard for 6 months.
Be sure to identify it on your recommissioning check list so it is replaced before restarting the engine.