I am following this closely as I have the identical problem. Please post
results when you install the new rectifier.



"Chunky" wrote in message
u...
Well the saga continues:-

Drilled the holes, no difference.

Took out the thermostats completely, still no difference.

The mechanics I spoke to were stumped. Now I was getting really suspicious
of the whole overheating thing. Bought a multimeter and a digital
thermometer. I noticed while using the multimeter that one of the
rectifer/regulators (what takes care of the power coming off the
alternater
to charge batteries, ignition, accessaries etc.) was looking scorched. I
examined it further and realised it was burnt out. So the electric system
was limping along on 20 amps instead of 40. Ordered a new regulator.

I also checked the temperature sender with the multimeter to see how it
registered. I checked the ohms it out put along with the table that
converts
this to temperature. I also put the sender into very hot water along with
the digital thermometer. The temperature guage in the cockpit matched the
sender and the digital thermometer. Hmmm! So the guage was right and the
sender.

I then glued the digital thermometer between the cylinder head and exhaust
manifold near the send and took the boat out. The temp guage worked up to
200+ °F and then I checked the digital thermometer which showed 171 °F.
Tried a few times heating up the engine and checking the temp, 167, 156
etc.
So the guage reads high by 30-40° but it checked out ok when I compared it
on the beach.

I now suspect the loss of one regulator is causing the guage to read high
when the engine is running. When the engine is running fast the temp
appears
to go down when in actual fact the motor is simply generating more power.



"Chunky" wrote in message
u...
yeah i spoke to a couple of mechanics. One suggested drilling a 1/8"
hole
in
each of the thermostats to allow some extra water to run thru the system
until the poppet opens at 2000RPM. I have drilled a couple of holes as
described and will put it in the water tomorrow. It makes a lot of sense
because whenever the motor gets hot all i do is open the throttle and
the
temp drops like a rock.

Regards,

Kind of makes sense
"Boatriggr" wrote in message
...

Well I changed the impeller although the old one was in good shape
anyway.
Both have a brass hub.

Checked the thermostats and the pressure relief valve and they are
seem
fine.

Ran the boat again today again same thing. Idle no problem. Bring up
a
few
revs to get 5 or 6 knots and the temp goes to the red zone. Open the
throttle a little more and still the same until the RPM is about 2000
and
the temp drops. Crank it up to 20 knots + and the temp drops to 150F
and
all
is well.

One thing I noticed is that the tell tale is more of a dribble now at
low
speeds, and hot.



Did you ever reply as to what hull it is on?
Did you try changing the trim angle?

A cooling system can be tricky as there a a few instances where
removing
the
powerhead becomes necessary to check some things.
If you are not sure of what is going on it sounds like time to take it
to
someone with experience.

BR