79 Mercury 20HP Lower unit removal

J

jkennard

Recruit
Joined
May 7, 2012
Messages
4
Got this motor off a friend and have had some issues getting it to run and now that i have it running i have some more issues. The motor wont pee unless i fill the water pump up with water and then it shoots out. Im assuming its the impeller but i have no clue on how to get the lower unit removed. Ive been doing some reading and it doesnt seem that hard but i can't locate the bolts to disconnect it. Any help would be appreciated. I believe the motor is a 79 going from the serial number guide. Serial # is 5411979.
 
C

carholme

Rear Admiral
Joined
Sep 4, 2010
Messages
4,845
Re: 79 Mercury 20HP Lower unit removal

Not too sure what you are having trouble with. You say that it won't pee until you fill the water pump with water. How are you filling the water pump with water? Is the engine presently being run in a bucket of water or on the lake?

Gerry
 
J

jkennard

Recruit
Joined
May 7, 2012
Messages
4
Re: 79 Mercury 20HP Lower unit removal

I've been working with it on both the lake and in a bucket. At first it pee'd decent when i had it in the bucket but still not the flow i would expect. I put it on the lake a couple times and it drizzled out the pee hole if anything. Im not sure if theres a bunch of debris around the intake or what. I've flushed water through the vents with the muffs and everything but it seems like its slowly not peeing at all now.
 
Chinewalker

Chinewalker

Fleet Admiral
Joined
Aug 19, 2001
Messages
8,902
Re: 79 Mercury 20HP Lower unit removal

A good rule is that if you don't know when the impeller was last done, replace it.

No bolts holding on that unit - only studs. One stud comes up the front and has a nut just in front of the base of the clamp bracket swivel. Second one is hidden under the anode at the rear underside of the AV plate. A hole above the anode allows you too access the anode bolt with an Allen wrench - I think it's 5/16" but not certain on that. Once the anode is off you'll see the nut holding the rear of the gearcase in place. Once removed, unit should come off...
 
bobkyle2

bobkyle2

Petty Officer 2nd Class
Joined
Sep 2, 2010
Messages
159
Re: 79 Mercury 20HP Lower unit removal

Check youtube there are tons of great videos showing you the whole process
 
J

jkennard

Recruit
Joined
May 7, 2012
Messages
4
Re: 79 Mercury 20HP Lower unit removal

Okay i got my lower unit off and my impellor was no more. Question though this piece came out when i pulled it out and i have no clue where it goes. I feel like its a shield for something but its made out of plastic?

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