BoatBanter.com - View Single Post

On 19 May 2004 08:40:19 -0700, (Eldon Cutlip)
wrote:

Derek wrote in message . ..
On 18 May 2004 08:40:40 -0700, (Eldon Cutlip)
wrote:

"Greg O" wrote in message ...
"Eldon Cutlip" wrote in message
om...

So, I was thinking I must need have a semi-bad impeller in both motors
at this point. So, I just took apart the lower unit and pulled the
water pump on the cold motor. The impeller looked fine - no wear or
tear and still quite bendy. The inside of the water pump lining
doesn't have any scratches. So now I'm totally out of ideas.

Replace the impellers. even if they look good they may not be. A few years
ago my dad was up in Canada fishing and the engine was running hot. Removed
the leg and "flipped" the impeller over. The engine ran fine the rest of the
trip. The impeller got changed ASAP!
Greg

I replaced the water pump in the "cold" motor - or at least the one
that was cold originally After that, I had just enough time to
idle it for 5 or 10 minutes on the ears. It settled right at the mark
between the green and red. I didn't have a chance to get the other
engine's water pump done yet or to take the cold one out on the water.
But something still seems wrong even with the cold motor. I think I
will have to buy one of those laser temperature things. And I think
someone had mentioned that the oil to fuel mixture may be suspect.
Could running too lean cause the engines to run hotter? If so how do
I verify what the oil mixture is set to (these are the VRO Johnson
70's - 1986)? I had two of the local boat mechanics tell me the new
thermostats are the same as the ones I replaced.

So, I think the plan right now is replace the other water pump, get a
laser, and verify the oil mixture. I have no clue how to verify the
oil mixture but I guess I could just put oil in the fuel tank and see
if they stay cooler.

Thanks,
Eldon

Without verifying that both your gauges are accurate and reliable..
...... you could be farting against thunder!

Well, my thinking was that the laser temperature gun would tell me
exactly what temperature my engines are running at. I thought I could
then see what the guage was reading and "mentally calibrate" for my
guages. How else can I verify my guages are accurate and reliable?

Eldon

Wal-Mart sells mechanical temp gauges (made by Equius) for around $10.
They come with a good selection of fittings and mine is very accurate.
You should be able to install a "T" piece fitting that will accept
both your electric gauge and the mechanical one simultaniously. Try
vairying the the engine conditions (NEVER rev a motor above 2000
r.p.m. in neutral). The two gauges should follow each other closely.
Now, test the other motor. All done for around $15.

Just be careful not to kink the temp gauge line, it's filled with
liquid (alcohol, I think). Ideally, this test should be performed
under normal operating conditions.

Another method, but do this at your own risk, is to ground out the
wire to the sender unit via a selection of various resistors. For
example, if a 500 Ohm resistor takes the gauge to half, and a 200 Ohm
takes it to one quarter, it MUST do the same on the other gauge. Next,
remove the sender units and put them in a pot of warm water for a bit.
Using a digital multimeter, record the Ohms readings of both. Heat the
water a little more and repeat, all the way up to near boiling. I'm
guessing the readings should be within about 5% of each other.
Remember to make the readings quickly, for accuracy. Problem is, if
they're way out, which one is faulty???? This is why I preffer a
mechanical gauge over an electric gauge whenever possible, even for
Volts (joke!). Unfortunately, the pivoting and steering system of a
boat does not lend itself to these gauges, unless they're mounted on
the motor directly (another temporary option).

Okay, since I have a few minutes, and it were my boat, here's what I'd
do (at your own risk of course)

1) Replace the other impellor (water pump).
2) Ensure that all the seals between the pump and the head are good.
You could even be losing water pressure/volume from a leaking
seal or joint somewhere along that pipe (been there, done that).
3) Remove both thermostats, and leave housings open. BRIEFLY run
engines at idle and a little above. Both "fountains" should be
similar in volume and pressure (use drums, not ear muffs, for a
true simulation.)
4) Verify that both thermostats are working similarly, by using the
pot on a stove method.
5) Verify that both temperature gauges are accurate/reliable.
(also check for and clean any corrosion on any terminals).

Basically, you start at the beginning (pump) and logically eliminate
any discrepencies between the 2 motors.

I would also suggest getting a manual for your motor. They are
invaluable.

Good Luck.