Johnson raw water pump

[finefurn]

I have a Westerbeke 12b2 motor that has a Johnson Pump Model F35B-8000 which is used as the water pump">raw water pump for cooling. On the top of the pump between the input & output ports there is a screw hole in which only the bottom third is threaded. There was a screw there that had a deteriorated rubber washer that needed to be replaced. What is this screw hole for?

[belizesailor]

Normally for securing the cam inside the pump body. This cam is what causes the impeller blades to flex and generate vaccum. Behind the cover plate directly below the the screw hole you should see the cam, but maybe not with no screw hodling it there now. [emoji6]

Parts diagram for a Jabsco pump below showing cam and screw. Same concept.

http://www.pumpvendor.com/Jabsco_10550-200_parts.html

[finefurn]

Thanks Belizesailor now with a closer look at the internals I see that the cam is a separate piece and it all makes perfect sense. Guys like you are why I love this forum.

[belizesailor]

De nada.

That makes the cam replaceable, but in practice Ive never had to replace one.

[KadeyKrogen38]

FYI. Johnson used to use a bronze cam plate that was long lived. They now have switched to a nylon cam plate. One broke in a newly replaced pump on my boat and sredded the impeller. Had to remove heat exchanger to remove all the impeller bits and pieces. Bad modification by Johnson.

[Scrimshaw4]

I have a Westerbeke 82B4 that also uses a Johnson pump. Be advised the Westerbeke modifies the foot of the pump to provide pulley alignment with the mounting bracket vs aligning the bracket base angle. They do this so you either have to rebuild your existing pump (Johnson parts) or by their VERY EXPERNSIVE replacement pump from them.

[belizesailor]

Originally Posted by Scrimshaw4

I have a Westerbeke 82B4 that also uses a Johnson pump. Be advised the Westerbeke modifies the foot of the pump to provide pulley alignment with the mounting bracket vs aligning the bracket base angle. They do this so you either have to rebuild your existing pump (Johnson parts) or by their VERY EXPERNSIVE replacement pump from them.

Volvo does a similar thing. Johnson pump body with a square mounting flange specific to Volvo. Cant buy anywhere else Ive found, except from a Volvo Distributor.

[kinggeordie]

This could also be a bleed screw so that water can be put into the pump after maintenance so you’re not running it dry which disintegrates the impeller