Question re: Johnson raw water impellers

[rfinneren]

I have a Johnson F4B-903 water pump on my Yanmar 3GM-30F diesel. I'm looking to do an annual service on this engine and want to replace the raw water impeller and also carry a spare impeller. The previous owner has onboard a spare Johnson 810B impeller with a threaded pin inside. I'm seeing mention online of the Johnson 810B-1 impeller with a smooth pin and no paper gasket? I'm confused about the difference between the 810B and the 810B-1 impellers and whether or not they are interchangable? Does an impeller with a threaded rod have to be replaced with another impeller with a threaded rod? Or does this not really matter? Is the 810B-1 just the newer and backwards compatible version? I'm not sure what's actually on my engine yet because I haven't opened up the water pump">raw water pump yet. Just trying to figure out what to order.

Thank you!

From spxflow (parent company) website:
09-810B-1 F4 MC97 (for cooling)
Impellers | Johnson Pump - Marine | Product Detail

[RaymondR]

The threaded rod slides into a slot on the impeller drive shaft. As long as the OD of the threaded rod is appropriate for the slot it should not make any difference whether it is threaded or not. As long as the two impellers have the same dimensions they should be interchangeable, the difference may be in the material they are made from as nitrile rubber is required to pump fuel or oil with these pumps but the material does not much matter for raw water.

[rfinneren]

Thanks that’s very helpful!

[Calif.Ted]

I seem to remember pumps in the 90's using the paper gasket and switched to an O-ring about 2000. Replacement impellors from Johnson come packed with both gaskets and a little tube of impellor lube. I'm a little leery of using an impellor of unknown age out of the spares box if it may have had time to dry out and get brittle.

[S/V Alchemy]

Globe makes a series of "run-dry" impellers should you, for instance, suck a plastic bag over the intake. They can rotate until you notice the temperature rising or the alarm goes off (which I recommend). Just match the Johnson pump to the appropriate replacement. That's what I both have as installed and as spares.

[Zoidislander]

Originally Posted by S/V Alchemy

Globe makes a series of "run-dry" impellers should you, for instance, suck a plastic bag over the intake. They can rotate until you notice the temperature rising or the alarm goes off (which I recommend). Just match the Johnson pump to the appropriate replacement. That's what I both have as installed and as spares.

+1 for the Globe impeller, I have had really good luck with them.

[Gudgeon]

On my 4JH3TE the impeller is threaded and Yanmar makes a tool to screw into the impeller for removal. With out this it is very difficult (near impossible) to remove due to access to water pump/impeller. I now ensure the impeller is threaded as I did one with out the threads and it took many extra hours. You may have much better access than I do.