Sometimes there is a smaller filter in the carb where the fuel line
goes in. If it does not have a big fuel filter/water separator then
this smaller filter clogs easier. You can test the fuel pump by
disconnecting it from the carb and having someone hold the end of the
line in a small can or jar while you crank. I'd guess you have a fuel
pump problem. Some of the fuel pumps can be disassembled and cleaned.

You should also check the lube in the outdrive before you attempt to
use it. It should be full to the top plug on the side. Then you can
carefully loosen the lower plug and let a few drops of lube out. If it
has water in it you might have a problem. You probably should change
it in any case since you don't know how old it is. If it does not have
water in it then changing is not an emergency. If the outdrive has
water in it you really need to change it. And then check it again
after you have the boat in the water for a while to see if water is
getting in the outdrive. That is a common cause for failure.
Outdrives have to filled by pumping the lube in from the bottom plug.
Just to top one off that is a little low some can be added at the top
plug.

The other thing you will need to check is the raw water pump. These
drives have a rubber impeller style water pump in the middle of the
outdrive. It pumps water up into the engine cooling system. They wear
out fairly regularly from age, sand, etc.

Do you have a set of water muffs hooked to a garden hose? You do not
want to run the engine from more than a half minute or so without
cooling water. The exhaust has rubber parts in it and relys on the
water cooling the exhaust to prevent the rubber parts from gettng
melted.

Clymers has a pretty good manual for these that is not too much. I'd
recomend getting one if you can. Might have to shop ebay for one old
enough to cover 1975.

Before spending any money you also might want to look the hull over
pretty carefully. These boats were mostly built by encapsulating wood
for some of the structural parts like the floor, the stringers (the
boat equivilent of floor joists), and the transom. On older boats this
wood may have gotten wet and rotted. Usually you can tell because the
remaining fiberglass is too flexible or the floor feels soft.
Replacing the rotted wood is a difficult and unpleasant task. Rotten
stringers or transom is often the single thing that makes an older boat
not worth repairing. It would be good to get an idea what condition
they are in before you start spending on engine parts.

Rand_man50 via BoatKB.com wrote:
The gas that was in the tank was very old, about three years, so I drained it
out and put 5 gallons of new gas in it. The engine is a mercruiser 140. The
slow cranking was just because I had light duty jumper cables so it wasn't
getting enough power to the starter. When I connected the battery to the
terminals it cranked fine. It's possible that there is rust and other crap in
the tank. Is the fuel filter/water separator inside the tank or outside
somewhere?

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