"Jeffrey P. Vasquez" wrote in
message . 17...


Your diagnositcs seem to point clearly at a pump issue. More further on -

Okay, not just *very* familiar, but spot on exact. However, if I am
understanding your description, it seems you were in the act of
rebuilding or partially rebuilding the water pump prior to the fault? Is
it possible that simply opening the back plate, removing the worn
impeller (worn, but no missing vanes), installing a new impeller,
replacing the gasket and replacing the backplate could result in the
sudden occurrence of this shear issue? Could the friction generated by
the fresh rubber of the new impeller (and possible dry running, though
the engine manual says dry-running will destroy the impeller in seconds,
which it didn't or wasn't) have caused a shear issue between pulley and
shaft where none existed before?

Possibly.

You didn't mention removing the cam, so I'm assuming that's still in place.

Depends on your gasket thickness, the length of your replacement
impeller, and how stiff it is on the shaft.

Too long an impeller, or too thin a gasket (or both!) can cause
the impeller ends to seize against the cover plate once the cover is
tightened up. At the next start, the shear occurs.

Also, if the impeller is a very tight fit on the shaft, it may be pushed in
too hard and jammed against the back plate, or it may be standing a little
too proud and jamming against the front plate. At the next start . . .

Missing out a gasket obviously also has the same effect.

With a raw water only system you'd overheat pretty quickly. Your test
separating the pipe at the engine block and seeing no water entering the
block eliminates the most common blockage problem, which is the slow build
up of calcium and borate salts in that areas which regularly cycle through
hot and cold. Also, this type of build up is over the years, not days!

Sorry you're not having fun! Barked knuckles, hacksaw mashed screw slots,
lost screws in the bilge drains and used diesel oil deodorant and finger
colouring does all seem to be all part of the game. No wonder my wife tells
me not to hand the bread to our visitors!


I have read that water flows through the water pump without rotation of
the impeller.

Not significantly. You'll get a drip rate around the backplate and endplate
if there's a positive pressure, more with wear. Any more and the gasket's
too thick or the impeller too short (opposite to the seizure problem). This
leakage is trivial compared to the pumping capacity of the vanes.
--
JimB
Yacht Rapaz, sadly for sale:
http://homepage.ntlworld.com/jim.bae...cification.htm
jim(dot)baerselman(at)ntlworld(dot)com