Six Times? No Seven!

Boot Key, Florida N24 42 W81 05
January 9, 2006

Today our mission was to fetch mail, groceries and a new thermostat for
the engine, then install and test the engine with the thermostat in.
We accomplished the first three tasks and were back on the boat by 1300.

The fourth task illustrates my lack of mechanical skills. First, when
assembling tools to do the job I found the missing thermostat. My taxi
trip to the next town to buy a new one was unnecessary. Sigh. That's
Murphy's law.

The thermostat lives under the coolant header tank. I have to remove
the whole tank to get to it. I pumped out the coolant disassembled it,
put the new thermostat in, then put it back together. It took about an
hour. When I put antifreeze in however, it leaked out. Libby helped
me to pump the antifreeze out and I took it apart again. That's one.

The second time I added some paste "form a gasket" from a tube, but
after I was done it leaked again! That's two.

The third time I looked more closely. I could see that the thermostat
should go under the gasket, not above. I put it all back together
again. This time it didn't leak. Horary. I started the engine. It
began to warm up at a normal speed. Hooray! I revved it up to 2000
RPM. After 5 minutes, I looked again. Overheating! Oh no. I quickly
shut it back down. One of the hoses to the heat exchanger that I
installed yesterday had popped off and spilled all the coolant. That's
four.

I replaced the hose, and refilled the coolant. But there was a
discrepancy. I pumped up two gallons of coolant from under the engine,
but only one gallon would fit back in the tank. I started the engine
and watched carefully. It started to overheat. Darn, that means that I
had air trapped in the cooling system below the thermostat.

I pumped out the coolant, took it apart again, removed the thermostat,
put it back together and let it run for a while. Now the air came to
the top and the chambers below the thermostat were filled with water.
That's five.

I pumped out the coolant, took it apart again, replaced the thermostat,
put it back together and let it run for a while. Except this time I put
in the old thermostat because I knew that one opened at the correct
temperature. That's six. Now it warms up only a little with the engine
idling, but it's after dark and I shouldn't make too much engine noise
because it will disturb everyone else. In the morning I'll finish
testing and we'll take it out of the harbor and drive around for a sea
trial.

The good part of the story is that each time I took the thing apart and
put it back again, I got better at it. It took an hour the first time
and only 15 minutes the 6th time.

I think I also spotted the oil/fuel leak that has been plaguing us for
months. It is the fuel level sight gauge, not the engine. I can't
repair it until that fuel tank is empty or unless I'm willing to spill a
gauge full of fuel deliberately. I'll wait. Meanwhile I'm glad to know
what the problem is.

Does it seem to you that I spend too much time fussing with the engine
if we are sailors? I agree. The catch is that we're hooked on all
these electrical conveniences, lights, radar, computer, refrigerator,
that draw from the battery so I need to run the engine every day to keep
the batteries charged. We also find that about 1/3 of our voyage so
far is under power versus 2/3 under sail. No wind, wrong wind
direction, narrow channels and canals are the reason why we must motor
some of the time. Also, Florida drawbridges won't open for you unless
you have a motor. If you sail with no motor there's no upper limit to
the time it might take you to sail under the bridge.

Update January 10: We weighed anchor this morning and sailed out to sea
to test the engine. Our plan was that if everything was successful, we
would depart directly for the Everglades.

The results were mixed. No overheating even at high RPMs that we have
never managed since we bought Tarwathie 11 months ago. Our chronic
cooling problem is solved. Hip hip hooray!!!

On the other hand, the engine temperature rose to 140 degrees and stayed
there at all speeds. That's too cool it should be 190 degrees F (88C).
We motored back to the harbor, anchored, I pumped out the coolant,
disassembled, replaced the old thermostat with the new one, reassembled,
and refilled the coolant. That's seven.

This time it worked as it should. I started the engine, and the
temperature promptly rose to 190 degrees and stayed there. No water
leakage. No fuel leakage. No oil leakage. Sigh. I hope this is the
end of the story. Tomorrow at first light we'll set sail.

Now for the post mortem. Warning to readers. The rest of this article
is technical. Skip it if you're not interested.

The whole problem started with Al Hatch (the previous owner of
Tarwathie).

On survey day he said that he wanted to change the pitch of the
propeller because the engine was running hot, indicating that it was
working too hard. He declared it a success, but I couldn't judge
because I didn't know Tarwathie's normal operating parameters.

Al's diagnosis was wrong and the wrong diagnosis led to lots of expense
and anguish for us. The correct diagnosis would have been that the heat
exchanger became less effective year by year for 30 years of life. For
the first 29 years, the effect was invisible because the thermostat
would just open a little wider every year. When the thermostat
couldn't open any wider, the engine temperature would rise instead. The
problem would be worst in warm tropical waters and less bad in cool Lake
Champlain waters.

In Jacksonville last June the problem go so bad that I could only make
one knot under power.

In Fernandina Beach where I hauled the boat out to paint the bottom I
paid a diesel mechanic $400 to solve the cooling problem. He took
things apart and cleaned them and back flushed and changed the raw water
pump impeller (which wasn't needed). He also broke the seal on the raw
water pump and replaced. The engine performed somewhat better. We
could do four knots. However we may have been motoring in cooler
water.

In New Jersey in July it got worse again and I paid another mechanic
$250 to clean the heat exchanger and to remove the thermostat. The
result was another incremental improvement. We could do 4.4 knots.

On the Hudson river I hauled the boat again and restored the propeller
pitch. It caused another incremental improvement. We could do 4.7
knots. Libby and I thought we could live with that indefinitely.

In December when we got to Southern Florida the problem got worse again.
Our maximum speed reduced to three knots. I was convinced that we
needed a new primary water pump. That was the only part we never
replaced or inspected.

In January in Marathon I found John Moore, of Moore's Marine. I told
John about the primary water pump and he said, "No way. Tell my your
symptoms." I told John the whole story. It was like being on Car Talk.
He said all the evidence suggested that we need a new heat exchanger.
Despite the fact that we cleaned it, heat exchangers like car radiators
build up films and deposits that reduce the heat transfer coefficient.
I believed him and invested $500 in a new heat exchanger. John's
diagnosis was the right one.

In total we spent $1560 dollars to fix the problem rather than $500 if
we had the correct diagnosis at the start. Worse, was the over 400
hours of motoring worrying about the engine temperature and traveling
slower than we would have liked to. Oh well. A mitigating factor is
that I got a lot of schooling and experience as a diesel mechanic along
the way.