[OMC-Boats] running rough....

Wow what a journey. Boat spent all last summer in shop.
Originally went there for timing/rough running sort of problems. It
would lose all power at about 1/2 throttle. Different things were
tried, carbs cleaned, points, distributors even a different
engine. Finally got everything running seemingly well. Water test
showed that it went to almost full throttle w/o previous power
drop. BUT during that testing new problem arrived - overheating
within 1-2 minutes. Was running 200+ in minutes of being
underway. Rest of summer spent trying to figure that out to no
avail. End of season took away from mechanic unsolved, and now
this season have been trying to figure it out myself. Basically
trying to clean everything the water passes through. SO - the good
news is that yesterday at the dock the temp issue was solved, and I'm
too embarrassed to say what it was. But a hose reversed has
something to do with it. Couldn't believe it. Yeah, It should've
been caught somewhere, but nobody ever noticed as all focus was on
the non-obvious stuff. So now temp issues seems solved - running at
about 160 - 180. Perhaps a little hot, but way better than the
needle shooting up towards 225 after about 2 minutes. I ran
around out there for 20 minutes straight without it going over
180. Happy!!

SOOOOO - that's the condensed history. Now the bad
news.....everything was running great at nearly full speed for 20
minutes. Slowed down, sped up, etc. But then it started to be
do a bit of what it was doing way back when when I originally took it
to the mechanic. Not as bad, but similar. What's happening is
sort of combination of two things - perhaps related or not:

1) Upon acceleration to plane, it feels like something is sort of
"slipping", almost like when you are driving in a car and your tires
are slipping while trying to get some grip on gravel or something. I
can even hear what sounds like a sort of slipping sound. It might
be cavitation, but not really feeling like it so much. Plus with
the motor lowered all the way down as is should be, there really
should ever be any cavitation should there? It's almost like a belt
slipping. Not anything as harsh feeling/sounding as metal gears not
meshing up. The belt tension seems good - moves about 1/2" either
way at rest. Is there a chance the drive could have moved up on
it's own a little and the finger joints weren't meshing? Can it move
like that? I didn't bump the tilt knob or anything. Only happens
when trying to get to plane.

2) Upon acceleration to plane, i'm don't have the full smooth power
I had. If I move the throttle very slowly up, it eventually gets
there. But moving it up normally, the carb hisses and I have no
power - it bogs down. This is similar to what it did last
season, except I couldn't EVER get it to have enough power to get up
on plane.

On friday I have plans to take it camping at a lake 2 hours from here
for the weekend. Didn't think it was gonna happen due to temp
problem, but now that that's resolved, i'm gung ho! I can deal with
the engine not running perfectly for one weekend. It hisses and
"cavitates" a bit, but eventually gets up to plane if i go slow.
I don't have time to do any full on timing light tune up, and don't
want to risk making something worse and grounding me. BUT last year
before temp prob, I remember being out there on the water with a
screwdriver adjusting the two screws under the carb with the mechanic
coaching me on the phone. So:

1) If I understand better conceptually what is happening, I can often
"figure stuff out" better without help. So without getting to
technical, what is happening when I hear that air hissing noise
coming from the carb when i try and accelerate fast? Is that a lack
of gas issue, or a lack of air issue?

2) What is happening when I adjust those two screws? And what is the
proper way to do that? I seem to remember him telling me to turn them
all the way in one direction until the engine almost stalls, then
back slightly. Can't remember which direction. Both at the same
time? One first then the other?

Sorry this is so long, gotta get everything in - i'll be at my shop
working on boat and checking email from my phone - thanks! Jeff
Received on Thursday, 18 June 2009