"Jeffrey P. Vasquez" wrote in


This time there was no curing it. I dismantled everything upstream and
downstream of the water pump and it appears there is no flow through the
water pump even though everything appears to be functioning exactly as
it's supposed to. The impeller is fine, the belt tension and pulley
function are fine and there are no blockages from the through-hull to its
egress.

"JimB" wrote in message news:...

snip
You can check most pumps by taking the cover off and turning the engine over
with the starter while holding the fuel cut-off. If the vanes don't turn,
there's a shear failure somewhere or a missing key, and that's your problem.
If they do turn - your pump is almost certainly OK. Back to the partial
blockage . . .

Have fun. Maybe someone who knows your Yanmar will give you a better story.

I had a VERY frustrating overheating problem, sounds VERY similar to
what Jeff describes and Jim has Almost focused on what the problem
was . For me it was very frustrating, check strainer, check hoses,
check impeller, (still overheats) check pump (ok), pull exhaust
(still overheats), replace w new impeller (still overheats) put in 2nd
new impeller (still overheats) damn thing would run FINE at idle in
the canal, when I get out the channel and pick up rpm it would
overheat., seastrainer clear from beginning, no air leaks.

take pump cover off, R&R impeller & never find anything wrong. Put it
back together and runs fine at idle. (sound familiar Jeff?)

Finally I discovered what was happening was what Jim alluded to -- a
shear failure. Where the pulley fits on the water pump shaft was the
problem. There was enough drag to (pump off engine) to turn the pulley
by hand and observe the shaft spin & impeller turn (offering NO CLUE
because it APPEARED to be OK). Under load the drag was overcome and
EVEN THOUGH I could see the belt spinning the pulley, the drag on the
impeller overcame the shaft/pulley drag .

The problem was Both the pulley and the shaft, couldn't just relace
the pulley had to replace the shaft, to replace the shaft needed new
bearings and seals & by the time you add the shaft, bearings, seals, &
pulley together as a parts order it made more sense (cents!) to just
buy a new pump assembly (not cheap either)