Merc 7.5 powerhead interchangeability?

D

dicktaber

Petty Officer 2nd Class
Joined
Sep 3, 2001
Messages
183
Hello once again. You guys have always been able to answer my questions so I'm coming back. I have two "project" Merc 7.5's; one is a 78 s/s and one is an 81 l/s. Neither runs, bought them as a package deal. The long shaft (81) is seized up big-time, power head is basically junk (broken bolts, etc) but the external components (carburetion and ignition) components are useable. I have a chance to buy a bare powerhead (no flywheel, ignition components or carb) that is supposed to be a 70-73--S/N is 3275468. Finally, the question--are all of the powerheads of this era interchangeable? <br />Thanks as always, and maybe this winter I'll get to some of these projects...
 
Chinewalker

Chinewalker

Fleet Admiral
Joined
Aug 19, 2001
Messages
8,902
Re: Merc 7.5 powerhead interchangeability?

Hi K2M,<br /> There is a lot of interchangeability between groups of years, but I think '70 to '81 might be pushing it. They completely changed the ignition system which means different upper main cap, crankshaft, mounting bosses, flywheel, etc. I'd look for something mid-late 1970s to early 1980s...<br /> 9.8hp powerhead would work, too - you'll need the 9.8 carb, too.<br />- Scott
 
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