If you sucessfully awake this motor, you MUST install a new impeller, and renew every year. Otherwise you're at extreme risk from cracking the block from overheating, if you lose your impeller. I've personally seen those results and they ain't pretty. Almost impossible to weld up the block after it happens, so it's cheap insurance to keep the impeller fresh.
There is also a mod to move the telltale hose from its present position to the top of the block. This keeps the inner water passages flooded all the time and eliminates the chance of having a pocket of air or "steam" at the top of the block, giving inadequate cooling to #1 cylinder and potentially cracking the block. Mercury moved the telltale on later models.
Here's some info I saved about the location of the new telltale hole:
7/8" forward of the split line between the rear water jacket and the block,
(where the gasket is). and 3/4 inch to the left of the ridge that runs fore
and aft above #1 cylinder. Use a plastic 1/8" pipe thread fitting.
Another must-do on these is to make sure the prop pitch is low enough to let the engine run up into its rpm range (around 5500 rpm at full throttle). The displacement is only about 44 cubic inches, doesn't make a lot of torque, so the engine needs to wind up to make power. If you lug this motor, you'll kill it.
All that being said, if you have a good one, they are lightweight and work well on a light boat, with good economy.
HTH & G'luck..........ed
