Why the name Raw water? well in the case of a marine diesel engine the cooling is normally done by taking ,sea water directly from the sea and then either cooling the cast iorn block directly,or cooling the engines fresh water heat exchanger which runs a fresh water coolant through its pipes.The sea water is used in one pass over the heat exchanger pipes then dumped into the exhaust exit just where it enters the rubber exhaust pipe,then out through the exhaust and back into the sea.
Jabsco and also Johnston make similar pumps,many parts are interchanglable,just be sure you carry at least one spare in case the one in service fails.
Impellors for the Perkins 4108,the BMW/Hatz and the Yanmar GM10 diesels.Note the contents of each box,some impellor kits contain only the rubber impellor,some have gaskets and even new face plate screws,its good to carefully inspect the kit before buying it?
The small impellor fits the Yanmar GM10,part number 21414-0001B,the pump is mounted low down on the front of the engine,its not in the best of places as the main fan belt pully masks one of the three bolts holding the raw water pump in place.Its as easy to remove the entire pump body and work on it on the bench.
Note,if you do this,do not turn or crank the motor with the pump removed!
Raymond from Manex Marine, once suggested a similar sized Jabsco impellor,saying it was the same shape and R10 cheaper,it fitted too but soon stripped its center drive,as it turns out the Yanmar pump requires an impellor thats about 1mm thinner,so check that part number,the Jabsco part book mentions the correct Yanmar one.
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