In the case of a marine diesel with a heat exchanger we need two water pumps,one is the raw sea water pump,normally with a rubber impellor but another pump that is often fitted to the front of the engine as found on most automotive applications.
This is the water pump from a Perkins 4108 diesel,it may well fit other Perkins applications too.
The inside which runs in the coolant,I say coolant as you should always have an additive such as antifreeze to stop rusting in the engine block.
The impellor is supported inside and at each end by sealed ball bearings,they in turn are protected by carbon face seals,they are cooled by the liquid around them,so never run the system with out coolant and do not over tighten the fan belt as you will probably damage the bearings?
The front end of a Perkins 4108 diesel,which is a four cylinder engine giving around 46 bhp depending on use.The upper left pully powers the fresh water system,the upper right unit with the round plate and six screws is the Jabsco raw water pump,this is driven by an internal key way inside the engine.
Sample water pump seals,these are not off the Perkins 4108 engine but are ex stock off another application.
Carbon water pump seals,three new ones in the front,the rear ones are used but servicable.These may be outside the ability of some to fit,we need a press to remove the pump shaft as a start,I would recomend anyone going cruising to either carry a spare fresh water pump,or the correct seals and bearings as a kit,to enable a pro motor engineeers shop to rebuild your pump for you.
Note,failure of these pumps tends not to be instant,you will normally note a slow drip from the escape hole provided in the pump,when this is seen make plans to either change the pump then or as soon as you reach port.
R McB
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