Mercury Mark 6 Comet twin

jml255

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Joined
Jun 7, 2013
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7
I purchased a boat with an old mercury mark 6. It was missing the pull cable. I replaced it and got it started. I noticed it wasn't pumping water out the 4 holes half way up the shaft, so I started to investigate. Is the open hole in this picture the drain plug for the oil in the lower unit? What type of oil should I put in the lower unit? Any tips on taking it apart to see what needs to be replaced to get the impeller doing its job?IMG_20130607_190505.jpg
 

jml255

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Jun 7, 2013
Messages
7
Re: Mercury Mark 6 Comet twin

Also the motor has a s/n of 33960 from the plate just below engine. these numbers don't match any range I have seen to identify the year.
 

jml255

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Joined
Jun 7, 2013
Messages
7
Re: Mercury Mark 6 Comet twin

Also the motor has a s/n of 33960 from the plate just below engine. these numbers don't match any range I have seen to identify the year.
Ok so i spotted the 11 before the 33960 so this is a 1958 model.
 

Chinewalker

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Aug 19, 2001
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8,902
Re: Mercury Mark 6 Comet twin

Yes, that is the grease hole. Vent is a smaller screw in that little divot just above the AV plate.

It won't so much pump water out those holes as mist it. Those holes are an exhaust relief. Regardless, if the motor is new to you, replace the impeller as a matter of course. Not a huge project on those little buggers, but it does take some care in getting the neutral clutch cable fed back through and readjusted, etc.
 

jml255

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Jun 7, 2013
Messages
7
Re: Mercury Mark 6 Comet twin

IMG_20130616_190045.jpg

I am trying to figure out what else may be wrong beside the impeller needing to be replaced. I see water coming out of a wierd place. Is more than exhaust supposed to come out? See my picture
 

jml255

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Joined
Jun 7, 2013
Messages
7
Re: Mercury Mark 6 Comet twin

I am pulling the lower unit down and loosened the shift cable. If this drops back into the tube, will i be able to get it back through the tube? Also the clutch spring doesn't want to come out of the 2 pieces, is there a trick? I filled up the LU with oil for my test and it all leaked out and had some water intrusion. SOme of the bolts were loose and I think it needs a new prop seal.
 
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