I have the guage in the bottom of the water manifold where they feed to the
fuel coolers and eventually out the pee hole.
Thelflex suggests that as one of the points. This is all with the boat in the
water running. It will not fail on a trailer. The boat needs to be pushing
water to be running hard enough to overheat.
With the thermostat out it acts similar at speed, overhreating around 4000, but
up to about 2000 RPM this thing won't even get hot enough to make the computer
happy (100-110 degrees, without the thermostat). It runs like a car in "limp
home mode".
I only tried that once, just to see if there reallty was TWO bad thermostats.
(I am on #3 now in the $300 hunt).
I really think this is just not pumping enough water and under a load it
overloads the ability to cool. Simple huh?
You can see why I really want to swap the whole damned foot.

I guess, if you haven't already, find out what the recommended pressure is.
I located my info for Mercurys (with a "Mercury" gauge). The lowest is
"6-12psi" for 50/60/65/70 3 cyl and the highest is "15-25psi" for a lot of
engines, most all the V-6's and all #'s are at "above 5000rpm".
I'm with you---2-4 psi isn't enough. A phone call to any dealer service
dept should get you the specs. My bet is either a leak or restriction
between the pump and the block. 'Course, it could also be a blockage before
the pump. It's easy enough to change the foot which, like you said, would
confirm or eliminate "half" the potential problems.
Good luck.
LD

"Greg" wrote in message
...
I have the guage in the bottom of the water manifold where they feed to
the
fuel coolers and eventually out the pee hole.
Thelflex suggests that as one of the points. This is all with the boat in
the
water running. It will not fail on a trailer. The boat needs to be pushing
water to be running hard enough to overheat.
With the thermostat out it acts similar at speed, overhreating around
4000, but
up to about 2000 RPM this thing won't even get hot enough to make the
computer
happy (100-110 degrees, without the thermostat). It runs like a car in
"limp
home mode".
I only tried that once, just to see if there reallty was TWO bad
thermostats.
(I am on #3 now in the $300 hunt).
I really think this is just not pumping enough water and under a load it
overloads the ability to cool. Simple huh?
You can see why I really want to swap the whole damned foot.

"Greg" wrote in message
...


It will not fail on a trailer. The boat needs to be pushing
water to be running hard enough to overheat.

When you measured the water pressure, was that sitting at idle, or while
running? Does the motor have a "pee hole", and if it does, can you see a
good stream of water coming out?

I am wondering if the problem isn't some factor involving the boat, like
maybe the motor is mounted too high and the pump is sucking air. That could
be a problem when the boat is up on plane, but shouldn't be a problem while
sitting idle.


I really think this is just not pumping enough water and under a load it
overloads the ability to cool. Simple huh?
You can see why I really want to swap the whole damned foot.


The first thing I would try is to remove the foot and disassemble the water
pump. Clamp on the "ear muffs" to connect the water hose and turn the water
on. The pressure from the hose should send a good stream of water into the
pump housing.

If that looks good, then the next thing I would try it to connect a hose to
the water tube that goes up into the motor. You should be able to come up
with some combination of hoses and fittings that will allow you to clamp a
hose to the water supply tube. If you want to get really fancy you could
throw a T on the faucet and connect a pressure gauge so you can see how much
pressure you are putting into the unit. Turn the hose on and see how much
water flows. If you have your engine water pressure gauge working you can
see how much hose pressure is required to get the desired engine manifold
pressure. That might tell you a lot.

You mentioned that they had to replace a broken housing. Was this a
thermostat housing? Do you have the old one? I am thinking that you might
be able to take the broken housing, modify it to add a hose barb and use it
to back flush the upper unit. If there is a blockage in the upper unit
someplace then creating a reverse flow might wash it out.

I suppose the worst thing is that you had some sort of critter get into
the cooling system when it was really small, and then grow to such a size
that it is creating a blockage and it can't wash out.

Rod

I am wondering if the problem isn't some factor involving the boat, like
maybe the motor is mounted too high and the pump is sucking air. That could
be a problem when the boat is up on plane, but shouldn't be a problem while
sitting idle.

The pressure is always low. This is either sitting, slow speed or up on the
step. I am still using the boat. (138 hours since it started) There is no
problem if I stay under 4000 RPM. With 50 square miles of manatee zones that is
not a problem.

If that looks good, then the next thing I would try it to connect a hose to
the water tube that goes up into the motor.

I have tried pushing water up the pipe. It seemed to flow pretty good with the
thermostat cover off but I didn't want to build up much pressure and blow a
gasket so I was just going easy with the hose.

I also back flushed it from the thermostat hole down to the pipe. It seemed to
flow OK but I don't really have a reference to how good that is supposed to be.



I suppose the worst thing is that you had some sort of critter get into
the cooling system


My biggest fear is that "critter" is something the first dealer did.

The last words out of his mouth when I left it with him was "if this thing was
running a little hotter it wouldn't make oil" and some mumbled reference to
cutting off an impeller ear. I'm afraid they did something.

The next step is probably pulling the water manifold cover and looking for a
dead rat but that is going to be the dealer, not me.

This will come across the wrong way, but I hope you don't get it fixed for
another week or so. This is a really interesting discussion so far. :-)

This will come across the wrong way, but I hope you don't get it fixed for
another week or so. This is a really interesting discussion so far. :-)


It has been going on since October and the next time they will be taking a
swing at it is Tuesday so I think that is a safe bet.

"Greg" wrote in message
...
This will come across the wrong way, but I hope you don't get it fixed
for
another week or so. This is a really interesting discussion so far. :-)


It has been going on since October and the next time they will be taking a
swing at it is Tuesday so I think that is a safe bet.


Well, keep posting. Murphy's Law says this is bound to happen to MY outboard
at some point. If the last few years are any indication, it'll happen during
the week of August 14th, when I'll be on vacation, trying to fish for 19
hours per day.