Hello, I have an older 1990 Bayliner with an I/O OMC Cobra 2.3L. I run
the boat in sal****er and it is equipped with a standard cooling system
(not a closed freshwater cooling system). The water pump was replaced
a couple of months ago so I don't think this is the problem.

Problem: Over the last few weekends, the temperature goes way up when
I start the boat (in the 200 to 250 range) and after a random amount of
time (usually 1 to 4 minutes), it suddenly drops back to its normal
range (around 125-150). In those few minutes, the engine runs really
hot (starts seing a bit of smoke aound the block and smell burning oil)
and I am always afraid that the engine is about to blow. At first, I
though I may have something stuck in the water intakes but this would
not explain why it happens almost all the times (beside the water is
pretty clear where I go). Once the temperature drops, it runs fine
for as long as I want and the temp stays in the 150 range.

Diagnostic: My untrained guess is that the thermostat is screwed up
and/or stick (rusty maybe?). It eventually "releases" allowing water
to flow through for proper cooling. To the experts out there, is this
a probable cause of my problem?

Fixing challenge: assuming this is the problem, I would like to
replace the thermostat. Not being mechanically inclined, I am
wondering if this is easy to do and if it can be done with the boat
still in the water at the marina).

A boater I spoke to this weekend suggested that I simply remove the
thermostat. He claims that the only thing a thermostat does is provide
faster warm-up when the boat is cold. However, the manual says "Do not
operate without a thermostat. This can lead to overheating and serious
engine damage". Comments?

I have the OMC manual which says "OMC thermostats used with standard
cooling systems are rated at 160F. They should start to open at approx.
157-163F and should be fully open at 182F.

According to the manual, the key steps to replace it a

1) Drain the engine block and exhaust manifold. (Do they mean the water
only? Can I do this with the boat in the water?)

2) Loosen the hose clamps and disconnect the hoses from the thermostats
cover. Remove the thermostat cover attaching bolts and lockwashers.
Remove cover with gaskets. Discard the gasket and remove the thermostat
(this whole Step 2 seems easy enough...).

Anyway, just looking for feedback, advice and suggestion regarding the
problem and whether I should attempt to replace it on the water (or
perhaps remove the thermostat entirely). My main problem right now is
I don't even know where to find the thermostat itself (or the hose
hiding it)!

Cheers! Andre

In article
.com,
says...
Hello, I have an older 1990 Bayliner with an I/O OMC Cobra 2.3L.

I don't consider myself an expert, but have the same drive
and may have some ideas.

Problem: Over the last few weekends, the temperature goes way up when
I start the boat (in the 200 to 250 range) and after a random amount of
time (usually 1 to 4 minutes), it suddenly drops back to its normal
range (around 125-150).

I concur it may be a thermostat, BUT, it could also be the
impeller (on the stern drive). If the boat has ever been
run with the drive out of the water (or without a STRONG
flow from a flush tool) for 15 seconds or more, I'd suggest
the impeller melted down.

It's easy enough to check, either in or out of the water (if
out, be sure to use a flushing tool with a strong flow of
water).

Remove the sloped cover on the top/rear of the stern drive
(3 bolts). The round "cup" you will see near the top with a
small hose coming out of it is the impeller cover. Make
sure you have cooling water present and fire up the engine.
There should be NO water escaping from the area of the
impeller cover. If there is, you've melted down the
impeller. The cover is easily removed by taking out the
three obvious bolts.

Buy a complete rebuild kit INCLUDING the cover, replace it,
and be done with it.


1) Drain the engine block and exhaust manifold. (Do they mean the water
only? Can I do this with the boat in the water?)

Yes, Yes. Look for small diameter clear, yellowish hoses on
the starter side of the engine. Follow them up to the drain
valves.
--
Mark

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Your perception may be different.

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