What causes an outboard to run cold?

[Tana]

Guy in my neighborhood has a nice looking boat with a 1978 Mercury Black Maxx 150 HP engine. Says it runs pretty good, but has not had in the water for a couple of years. Says it does foul plugs, and runs on the cold side. Since looking around for a combo boat I can use for Puget Sound saltwater fishing and running around in freshwater pulling grandkids on tubes, what should I be concerned about with this motor? Cosmetically, the boat, trailer, and motor look great for that age.

Thanks,

Tana

[kickerfixer]

If it fouls plugs it could be a carb problem.
maybe he mixes his gas wrong. Runs cold, What
does that meen? ( does not idle) The old Mercs
had problems with the lavra seals ( crankcase seals)
If that is the case It would cost to much to fix.But
it could be a carb probleam to. You need to have a
tech check it out, you can get into a lot of money
buying used outboards without checking them out first.

[Salmonator]

I don't know if that particular year has thermostats but a stuck open (or missing) thermostat will make it run cold.

[Boat Doc']

It is common for that vintage of motor to load up when idling, be hard starting when cold and run rough up to about 2500 rpm. They do have a thermostat in each head that functions below 1800 rpm. If the thermostats are functioning but it still runs cold the poppet valve is probably sticking open. If you buy it be careful about trying to fix something that is normal for the vintage.

[Gundog]

It is common for that vintage of motor to load up when idling, be hard starting when cold and run rough up to about 2500 rpm.

I thought that was the definition of two stroke. Sorry I couldn't resist. :grin:
Mike