Hmm.. I'm doing up a 1GM as a standby motor
which has to be ultrareliable. I'm thinking of fitting an external water
pump, bypassing the built-on item.
If the people who supply OEM for Yanmar
can't get the impeller to bond reliably in the first place, I'm not sure I fancy my chances of doing a better job. I don't suppose there's any 'aftermarket' supplier?
I've been foster parent to a 23' trailerable offshore
sailboat with a 1GM-10 for the greater part of the last two decades, so I can understand your affection for this motor
- it's a wee sweatheart.
This motor would only have done a few hundred hours, certainly well under five hundred - both the owner and I prefer to behave as though there's no engine
It is still on either the original impellor or the first replacement, but the engine gets a maximum of three weeks in salt water
before getting pulled out and the whole system fresh water flushed, so you might be onto something there...
I wonder if there's another impellor of similar dimensions (identical, in terms of the tip diameter and blade width) made in another factory, with a decent bond - if the shaft journal were slightly bigger, it would be no major problem to machine it down.