I have a 2002 4 stroke 60 HP Merc.
I took it in for the 500 hr and everything was fine before I took it in. $437
later (a new impeller, plugs and an oil change) I have an overheating problem
when I go over 4000 RPM.
I get Mercury involved and they say go to another dealer. $350 later (lots of
easter egging around, a new thermostat, a housing THEY BROKE and another
impeller) and I am still overheating. I hooked up a guage and it is 4PSI until
the thermostat opens then it is more like 2PSI. RPMs don't seem to change it
much and whenever I get much over 3000 RPM I see the temp climbing. At 4000 it
is very hot and the beeper goes off.
I am collecting a white pasty substance around the thermostat that I think is a
result of evaporating salt water since the flow is so low. Even when it is all
flushed out I am still having the problem.

I have a 2002 4 stroke 60 HP Merc.
I took it in for the 500 hr and everything was fine before I took it in. $437
later (a new impeller, plugs and an oil change) I have an overheating problem
when I go over 4000 RPM.
I get Mercury involved and they say go to another dealer. $350 later (lots of
easter egging around, a new thermostat, a housing THEY BROKE and another
impeller) and I am still overheating. I hooked up a guage and it is 4PSI
until
the thermostat opens then it is more like 2PSI. RPMs don't seem to change it
much and whenever I get much over 3000 RPM I see the temp climbing. At 4000
it
is very hot and the beeper goes off.
I am collecting a white pasty substance around the thermostat that I think is
a
result of evaporating salt water since the flow is so low. Even when it is
all
flushed out I am still having the problem.


I know you have been around boats a while.
While this can be tricky to trace, basic troubleshooting should steer you to a
solution.
One thing I would ask is: Was the engine overheated?
I have seen the grommet where the water tube goes into the powerhead adapter
melt. That would limit the flow to the powerhead.
When they changed the impeller did they change all the gaskets?


BR

I don't think it ever got over 200 degrees. I have only heard the beeper a
couple times, mostly just to prove the high guage reading is real (they have
tried to tell me my guage is wrong)
If I shut it down to an idle immediately the beeper stops.
They said they pulled the lower end shroud and inspected the supply pipe and
gasket in that $300 easter egg hunt although I wouldn't bet on anything at this
point.
I watched him do the second impeller and they installed the complete kit with
the plates and grommets. The removed impeller looks brand new, as it should be
since it was, but the plate may not have been replaced the first time.
My neighbor has a motor similar to mine and I am thinking about swapping the
foot with him to cut this problerm in half but that is a lot to ask.

My neighbor has a motor similar to mine and I am thinking about swapping the
foot with him to cut this problerm in half but that is a lot to ask.

Greg,
That would be a quick easy thing to try. But you are right, it's a lot to ask.
In a perfect world your dealer would have one to try. I would not be happy
bringing my boat in for repair, paying good money, only to find out it wasn't
fixed.
The possibility of a blown head gasket /cracked head is there, but I would
personally eliminate the lower unit/ water pump first.2PSI doesn't sound like
much water pressure at 4000 rpms. What is the spec on it?

BR

2PSI doesn't sound like
much water pressure at 4000 rpms. What is the spec on it?


The best I can tell it is 16 lbs.
I had it out tonight and I start out at about 4.5 psi until the thermostat
opens and then I am back to 2 or so. I really think the water supply tube or
the manifold must be plugged. with limited flow the pump pressure will max out
at a pretty low RPM (water starts blowing by the impeller), then more RPM won't
do much for the pressure.
I am really thinking if I get back in there myself I will make a snake from a
screen door spring and snake out that pipe.

You may have given us a clue, with the low psi. Where did you take the
reading? top of the block? before or after the thermostat? Also, what is
your water source? Are you using the clamp on "ears" or is the foot
submerged? I'm not sure of the spec for your particular motor (my 200hp 2
stroke climbs up to 10-15 psi at idle and 20-25 at 4-5000rpms) but some
motors are half that. No matter, 2-4 psi taken properly at 2000-4000rpm
sounds way too low. Assuming the impeller is correct and installed
correctly, something in the line is leaking and preventing pressure from
building.

On another note, Are the new plugs of the same heat range? A "hotter" plug
could be the culprit.
LD

"Greg" wrote in message
...
I have a 2002 4 stroke 60 HP Merc.
I took it in for the 500 hr and everything was fine before I took it in.
$437
later (a new impeller, plugs and an oil change) I have an overheating
problem
when I go over 4000 RPM.
I get Mercury involved and they say go to another dealer. $350 later (lots
of
easter egging around, a new thermostat, a housing THEY BROKE and another
impeller) and I am still overheating. I hooked up a guage and it is 4PSI
until
the thermostat opens then it is more like 2PSI. RPMs don't seem to change
it
much and whenever I get much over 3000 RPM I see the temp climbing. At
4000 it
is very hot and the beeper goes off.
I am collecting a white pasty substance around the thermostat that I think
is a
result of evaporating salt water since the flow is so low. Even when it is
all
flushed out I am still having the problem.

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.