impellar change out 1975 mercury 850 (85hp)

[jeffandtat]

Hey I figured while i am waiting for my appointment to have my carbs rebuilt maybe someone can tell me how to change my impellar. does the bottom end just drop right out or do i have to un hook the shift rod from the bottom of the carb. this is a 1975 mercury 850 (85hp) has anyone done this ?is it easy?

 

[jake505]

Re: impellar change out 1975 mercury 850 (85hp)

well if its anything like my 69 merc 800 then it should be just drain the lower unit, pull the prop(i suppose you could leave it on but woudn't hurt to grease the prop shaft, something that should be done every year anyway), pull all the bolts and pull off the lower unit (if it has a similar unit to mine dont forget the bolt under the trim tab that one got me ) then the pump should be right there on top. don't know when you last changed your pump but they can be a little tough to get off if they're old i ended up having to cut mine off with a chisle and hammer just rember if you do do it on the side where the key is so if you cut to deep you just hurt the key not the shaft

 

[jeffandtat]

Re: impellar change out 1975 mercury 850 (85hp)

okay i dropped her down did the change out fairly easy but now going back in with lower unit does not want to flush up with upper unit..... it seems the spines are not matching up please help....

 

[Chris1956]

Re: impellar change out 1975 mercury 850 (85hp)

Make sure you grease the splines, and have the water tube installed in the white plastic guide. Now turn the flywheel until the driveshaft splines match, and then try to mate the shift shaft splines. Motor and control s/b in neutral.

 

[Moody Blue]

Re: impellar change out 1975 mercury 850 (85hp)

Further the what Chris1956 described. Don't apply grease to the top/end of the driveshaft, only the splines.

I have a heck of a time with my motor when installing the LU. I get everything lined up but the upper shift shaft seems to wobble around and not engage the shaft in the LU. I need to get my fingers in the notch at the front edge of the midsection (just above the LU) and manually move the upper shaft to align with the lower. Once I get that aligned it easily goes together. One other thing I do to help the assy is to put a little grease/oil on the exhaust tube and rubber gasket in the LU to help them engage.

 

[jeffandtat]

Re: impellar change out 1975 mercury 850 (85hp)

okay i will try when i get home from work. When i changed the old impellar out ( it didnt even look bad ) does it matter how you orientate the impellar blades if so how do you do that so that the impellar works the best with the bend in the blades........... thanks

 

[jeffandtat]

Re: impellar change out 1975 mercury 850 (85hp)

okay actually thought this was going to be easy..... Anyway I tried what you guys suggested by turning the fly wheel and i thought it worked but when i dropped the LU down it was in neutral and prop spinning freely now when i go back in with a 1/4 inch gap and turning the prop i am getting a light clicking sound one way and prop wont spin the other. shifter is in neutral .. help anyone know about impellar orientation for most effient water movement????????????????

 

[Chris1956]

Re: impellar change out 1975 mercury 850 (85hp)

Ratcheting of the prop means gearcase is in forward. You need to turn the shift rod CCW until it clicks and stays in neutral.

When you install impeller, turn driveshaft CW to seat impeller blades. Lube the impeller with some lite oil.

 

[jeffandtat]

Re: impellar change out 1975 mercury 850 (85hp)

thanks to all that contributed information impellar is in were in neutral and now i am moving back to the ignition and electrical replacements questions to follow.......