Merc KG7super clean bottom plug, slight miss

4

45calmuzzleloader

Cadet
Joined
Jul 5, 2010
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12
I have a 1950 kg7 I'm working on. Engine has great compression 130psi, new coils new condensers, great spark. Motor starts easy and idles pretty good. Slight miss at higher rpm's while running in a barrel. Bottom spark plug is super clean, top plug looks right. I have already replaced both exhaust baffle gaskets. Researching this problem tells me my lower crank seal may be bad. How hard is it to replace the lower crank seal? Thanks.
 
Chinewalker

Chinewalker

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Aug 19, 2001
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8,902
Re: Merc KG7super clean bottom plug, slight miss

Lower crank seal is pretty easy. Pop the powerhead off, GENTLY remove the lower bearing cap. Light tapping with a wooden block, moving from side to side, etc. Save any shims or gaskets used. Using heat (propane torch works for me), heat up the bearing cap with the bearing suspended over a clean surface. It should drop out of its own accord as the aluminum expands more than the steel of he bearing. You will now have access to the seal. Pry it out as best you can. A bearing supply house like Kaman Bearing should be able to match it up for you.
 
4

45calmuzzleloader

Cadet
Joined
Jul 5, 2010
Messages
12
Re: Merc KG7super clean bottom plug, slight miss

Thanks again Chinewalker, I did not know if I had to split the block or not. Glad I don't have to split to change the lower seal. Engine still has wire/lead warranty seal intact. By the way I found plenty of lower unit parts from a fellow listed in the salvage link at the begining of the forum. Now have an excellent, water tight gear case.
 
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