1956 Mercury Mk 6 ( Comet Twin) can only turn the crank backwards.

[brozner]

Just picked up a Comet Twin in "like new" condition. Including the owners manual and original factory tags. Motor has very little run time. I can manually rotate the flywheel in reverse direction (CCW when viewed from the top) but can't rotate in the correct direction (CW when viewed from the top)either by hand of with the pull start. With the plugs out I can feel compression on both cylinders. The plugs are clean as a whistle too. Prop does not turn in reverse with the above manuever. The Motor does have the forward and neutral feature which I am not familiar with. Cannot understand for the life of me why this is happening. Hope one of you Merc Guru's can shed some light on this.

 

[racerone]

My wildest guess tells me to check the lower unit.---------Sounds like it is locked up.-----Start with checking lower unit oil / grease.

 

[Chinewalker]

Yep, I'm with Racerone on that count. The lower unit has a spring that is part of the neutral clutch arrangement. If you turn the motor backwards, you are essentially loosening the spring's tension on the driveshaft. If you turn the motor clockwise, you are going into the direction of tightening the spring, so that it locks up against the non-moving bits below the spring. I would pull the lower unit off and have a look. You need to disconnect the shift cable up top so it feeds back through when you pull the lower end off.

A service manual will definitely help. Get OEM manual for 1965 & Prior Mercs as it will cover your motor's lower unit in detail. Those little 6's are powerhouses for their size and well worth putting a little effort into. If you're lucky, the housing, gears and shafts are okay and it just needs bearings & seals. Most bearings are available over the counter at a supply house like Kaman Bearing.