TOPIC: changing impeller on merc 400

I am having difficulty changing the impeller on my 1960 Merc 400. I have the lower unit off and the impeller removed. My problem is the impeller will not go all the way on. It will drop into the cup until it is about a 1/16 inch from the bottom and that is as far as it will go. I have installed a new key and a new impeller. I tried to force it in by using the cover but it stops at this point.

Factory replacement part or aftermarket.

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If aftermarket , then get the proper one at the dealer for MERCURY !

don't force it you will ruin it when you run it. clean the shaft well install the impeller without the key to make sure it will go all the way down and the shaft will turn freely. then insall it with the key.

Mercury part I bought it from Grubbs Marine.

I will try that this AM. Thanks

look to see if impellor is bottoming out in the Stainless cup. If it is, then either your impellor is wrong, doubtful given supplier used, or the cup insert has been lifted and this is what is unseated. There is a small tab on the bottom of the cup that keys it in to prevent rotation. Maybe you are hung up on thattab not falling into it's slot.
If impellor is not bottoming then as Dave said look for the key to be hanging things up, or junk on the shaft.
Randy

I can't get the impeller out now. I think I forced it too far. It is not bottomed in the cup.

problem is you did not clean the shaft well enough.(rust).now it is jammed on to thet rust.might have to destroy the new impeller to get it out.

after cutting the impeller back off with my dremel tool thus totally destroying it. I cleaned the shaft thouroughly with the dremel and some superfine crocus cloth. It did need some clean up. I then installed a good old impeller without the keyway and it went all of the way in with no issues. I then put the keyway in held on by some grease again she would not bottom out. I then removed this impeller (no destruction . To find that the keyway was turning up at the bottom. This is a new keyway I just bought so the shaft must be letting it slide out at the bottom. The key now does have a slight curve. I am going to order another key and impeller.
Any ideas on how to fix the shaft and get the cup out. I have a new pump cartridge but I do not have the puller.

if you have a new cartriage then you can destroy the old one and take it out in peices without tearing the lower apart. that is up to you.

always remember to clean your shaft!!!

That's what She said!!!!

yea I could not leave that one to rest......