How to replace Johnson raw water pump

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ColinR

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www.victoriashadow.co.uk
The F4B-9 pump on my Nanni 21 is dripping from the back, not the cover. It seems like the seal has gone. I think I'll replace the whole pump and refurbish the old one for a spare. I can't find any description of how to do this. Is it difficult? Can anyone point me to a YouTube tutorial or something, I can't find anything. Thanks, Colin
 
very easy repair or replace got the same engine and pump parts from asap and job is straight forward nanni manual or if i recall how to in box of bits just make sure shaft is very clean and unpitted otherwise not fitting new seals think all you need is circlip pliers and screwdriver and a 10mm spanner
im going to strip mine next week if want a video let me know
but im sure its on youtube somewhere
 
You may find a gear puller useful if you intend dismantling the shaft (of the gear). First time I did it, on an Volvo MD2020 (which is bound to be different), I used a wooden mallet - but a gear puller is better (and what I use now).

Its simple stuff, except on the Volvo you need very small, short, spanners and preferably a monkey as an apprentice. I chopped down spanners to make the job manageable.
 
thegasmannick said:
very easy repair or replace got the same engine and pump parts from asap and job is straight forward nanni manual or if i recall how to in box of bits just make sure shaft is very clean and unpitted otherwise not fitting new seals think all you need is circlip pliers and screwdriver and a 10mm spanner
im going to strip mine next week if want a video let me know
but im sure its on youtube somewhere
Click to expand...

A few pics or video would be great. I'll PM you.
 
There is a useful site published by Compass Marine called marine how to .com. it gives well illustrated and effective advice on things like rebuilding or servicing water pumps, changing alternators and other stuff that only occasionally needs doing, it is an american site but a good one.
I am away to google it and should be back with a link soon.

https://www.pbase.com/mainecruising/raw_water_pump

update

https://www.marinehowto.com
 
Last edited:
This is an old thread but the following may still be useful if like me you came across it in search of a solution!

I have the same Johnson F4B-9 pump on a 1984 (approx) Nannidiesel 390HE with the same leak where the pump body meets the engine block.
The leak is probably due to a lip seal behind the impeller.

The manual in the post above is useful for a diagram of the pump and I have attached the relevant page as a pdf

The following vid shows Johnson seal removal in general:
How to Change The Seal on Johnson Raw Water Pump

The seal is available from ASAP at:
Johnson Pump Seal 05-29-139 for C1AL, F35B & F4B Pumps

A service kit (Johnson 09-45587) which seems to include the relevant seal plus impellor and gasket etc is at:
Johnson 09-45587 Service Kit for F4B-8 and F4B-9 Pumps

Looks like I can replace this seal without removing the pump (having tried to remove the pump I think for removal I would need a puller)
 

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