Johnson F4B-9 raw water pump.

[Balbas]

My old Vetus uses one of the above pumps. I need to do the lip seals and so took it off, only to discover the shaft is bent.

I suspect I'm going to need to press the shaft out of the pump body and then the bearings off the shaft. But I don't want to set about it the wrong way and mess it up. Can anyone furnish me with instructions as to exactly how to rebuild this pump?

Also, the pump I have (10-5240-1) is discontinued and therefore buying a replacement is in the region of £400, but other Johnson F4B-9 pumps are not, and so they are available for a little over £100. Can anyone shed any light as to what the differences are? It seems weird that they have the same 'type number' and look the same (from photos anyway). I suppose I'm asking whether I can substitute one for another.

 

[scottie]

One could have a bespoke housing ?

 

[Balbas]

One could have a bespoke housing ?

My guess is more that its rotational speed - the Vetus max rpm is quite high at 3,600 - and pump output. But I just don't know.

 

[superheat6k]

This might help you find out the detail differences ...

https://www.dropbox.com/s/0w6acer1s8qtu87/Johnson Pumps (detailed).pdf?dl=0

 

[yoda]

The waterpump on my Vetus M3.10 was in poor condition and when I added up the cost of shaft, bearings, seals and an impeller to undertake a rebuild I found that there was only about £80 to be saved. I got mine from ASAP supplies. I think you will find that the same pump is supplied with a different drive piece pressed on to the input shaft and that is what determines the difference in price.

Yoda

 

[Balbas]

This might help you find out the detail differences ...

https://www.dropbox.com/s/0w6acer1s8qtu87/Johnson Pumps (detailed).pdf?dl=0

That was really useful, thank you.

I now know how to decode the pump type number and also having looked at the engineering drawing and parts diagram, it seems that I may not have a bent shaft after all, but that for reasons I don't understand, there is an eccentric drive piece pressed on the end. Looking at the end of my shaft (engine end) when it rotates, it describes an elliptical pattern, which is why I though the shaft was bent.

I'm inclined to just replace the seals and see how I get on.

 

[Plum]

That was really useful, thank you.

I now know how to decode the pump type number and also having looked at the engineering drawing and parts diagram, it seems that I may not have a bent shaft after all, but that for reasons I don't understand, there is an eccentric drive piece pressed on the end. Looking at the end of my shaft (engine end) when it rotates, it describes an elliptical pattern, which is why I though the shaft was bent.

I'm inclined to just replace the seals and see how I get on.

If I recall correctly from when I did mine, the eccentric operates the fuel pump which is directly below the seawater pump.

Www.solocoastalsailing.co.uk