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Impeller Gasket replacement

D

Donald Boyer

Member
1989 Merc 90hp 3cyl, 2stoke

Hi all,

I'm putting a new impeller in my lower unit, and also replacing both gaskets, as I think the old ones are the originals from he factory. Whats the best way to clean up the stainless plate thats on the bottom of the pump, and also how do I clean up the area on the top of the lower unit that the pump is bolted to? All parts are dirty with old gasket pieces, gum etc etc. Should I just use sand paper??

Thanks,

Donald.
 
I just redid mine. The manual specifies the amount of wear in .001 inches that determines whether or not to buy the whole kit ($$$$) and redo the whole thing. Mine passed the test so I just did the impeller and it works fine.
Looking it up for you, from my 3 cyl 90 hp manual: "Replace plate if groove(s) (other than impeller seating groove) in plate are more than .030 in. (0.76mm) deep." The seating groove is the circular raised area on the impeller near the brass sleeve.

Mark
 
You can use a razor blade and small stiff S/S bristle brush, lube upper housing and install impeller in it so you dont tear upper gasket. Reassemble making sure key way goes into plastic center hub of impeller.
 
I work on my stuff. I do not work on marine engines for a living and if I did, would not want my workmanship to tarnish my reputation if I slacked off. It's a win-win, loose-loose situation. On the other shoe, needlessly replacing things that don't need it is cost to the customer that he shouldn't have to bear.

Had a Buick with an ignition problem. Regardless how it malfunctioned (and it was a lack of thermal heat sink compound beneath the trigger module making it fail when the engine got hot), I needed to get it fixed. My wife was in town, I was in the country. She got it fixed at a reputable Buick dealer in Dallas, TX.. After it was all said and done, the serv. mgr. said, in speaking with him about the huge bill for one failed electronics trigger module (which really hadn't failed, just shut down when it got hot due to no grease under it as I said), that we just shotgun the ignition and replace several components without testing or anyting like that. Get em in and get em out.

I quoted the manual. I followed the manual. I work for me. If it breaks it's me on me.

Be your own judge.

Mark
 
Thanks all.

One more question, does it matter what way up the impeller goes? There seems to be some small dots on it, which I'm pretty sure are just from the injection of the rubber into the mold when it was made, but just checking....
 
No, doesn't matter if it's new. If you pull it in future to inspect then it must go back on the same way.

Until you start using it the fins will be straight - they will bend opposite the direction of travel once it's been used.

And for my 2 cents - I wouldn't replace the plate either unless it was scarred up/grooved severely - gaskets are always a good idea to replace....
 
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