but the water was not so hot that I could not hold my hand in it.
The other water stream, which was mixed with the exhaust gases
in housing, remained cold. I suspected the water pump was bad.
I just replaced the water pump assembly, even though the components looked good. The motor started right up.
After a few minutes of running, it exhibited the same conditions as described above with the sputtering stream and small puffs
of steam. Could it be the engine block has deposits preventing the
water from flowing cleanly through it? If so, could I add an automotive radiator-flushing agent to the cooling water in the bucket,
and let it run through? Would that hurt the exterior finish or the
lower unit seals and rubber impeller in the water pump? Or could
it be the thermostat? — Capt. Tony Spasiano
Apollo Beach, FL
Tom Neale: The problem could be caused by many things,
most of which you’ve already guessed at. But one thing you need
to consider is that an outboard that old, particularly just sitting
most of the time, could have corrosion in its water-jacket com-
ponents, or even in the block and head. I assume that the block
and water jacket are aluminum, which would be particularly sus-
ceptible to corrosion if the motor was used in saltwater. Corrosion
could allow water and/or gases (which might manifest as “puffs of
steam”) to escape around gaskets. The puffs of steam may actually
be combustion gases or exhaust from a cylinder — which could
also cause the “sputtering.” You may have leakage around the head
gasket into your cooling water. If you see any white residue around
your coolant system gaskets, this is a sign of possible corrosion
where the surfaces meet. Having said that, I should note that I’ve
seen outboards with water-indicator streams that are plumbed
from the pump and don’t actually go through the cooling plumb-
ing in the block. Trace the hose back from the hole to be sure it
comes from the engine itself before you get too far into this theory.
Follow-up: Captain Tony later remembered a trick he’d learned
from his father. He filled the five-gallon bucket with hot water, added two
cups of Arm & Hammer baking soda, and ran the engine with it. He
reported to Tom that this solved his problem.
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