I rechecked the compression with the engine warmed up and its even on
all cylinders: 125lbs. That's good news. Before I tested it cold and I
had this nagging thought that maybe it needed to be warmed up first to
get an accurate reading.

After changing the wires and plugs, it starts easier and seems to run a
little better but I won't know until I get it out into the water where
I can put it under load. I am wondering if maybe I accidentally put too
much oil in the mix... after pulling the new plugs out (after running
it) they seemed a little oily.... might that make it run terrible?

JM

Chehalis Jeff wrote:
The tip-off was a LOUD buzzer going off in the control unit. Then I
smelled something when I stopped (old oil burning off the power head)
when I took off the outboard cover, I could tell it was hot. I let it
sit for a while and cool off (buzzer stopped buzzing), and then idled
back in (about 1/4 mi.) to the marina. Good thing it was a pretty cold
day. Immediately I assumed it was the water pump. I didn't hear any
predetonation - it was like someone was killing two of the spark plugs
- on and off - until the boat got on plane (took a bit) and then it ran
OK (not great, but acceptable.)

I just replaced the spark plug wires and spark plugs, but it's getting
dark and I am getting tired so I'll let you all know tomorrow if the
problem was solved.

JM



LD wrote:
What was the tip off that the engine was overheating?
It sounds like you know what you're doing and have thought about several
possible causes. I agree with you that it may be time for at least a new
set of plugs. You may have gotten it hot enough to deposit a little bit of
metal in the plugs that allow them to "pre-ignite" under load. Also, with
the high temp, you may have broken some of the deposits off the cyl head
that must be there after years of running. A good coating of deposits may
not cause a problem but with high temp, you may have cracked deposits with
glowing edges. In short, if the plugs and wires don't do it, I'd be ready
to pull the heads

"Chehalis Jeff" wrote in message
ups.com...
But he said all cylinder compression values were very close. If they
aren't leaking down, then how is that water getting in?

This is something that I have and are still considering as a possible
problem. I called a local OMC repair shop and that's what they
suggested - that when the engine gets warm enough and with enough
"suction" on the down stroke it could draw in just enough water (from a
'partially blown head gasket') to affect how it runs under load but not
enough to effect it otherwise. It's a possibility, however I would
think that there should be a way to tell if that's happening without
removing the head(s) and replacing the head gaskets. On the other hand,
that's not really a big, expensive or difficult job so maybe it's
worthwhile doing as a precaution.

JM