Thanks everyone for replying so far. I think I found the problem just
now, but want to bounce it off the experts.

I just found that my choke heat tube that runs from the manifold to the
carb was completely severed at the manifold.


My thoughts:
This means I'd been running her at full rich, and rather than leaning
out as we were thinking, I actually flooded her to death. No wonder when
I was lucky enough to start her warm, once I gave her more gas after
idle she'd stop. Also, it explains the hiss (manifold pressure) and what
I think happened was I had so much gas going into the cylinders that I
wasn't fully burning it and my exhaust was partially liquid gas,
entering the exhaust manifold/riser/exhaust outlet-- and that's what I
saw floating on the surface of the water & not an outdrive leak.

Also-
Good news is the oil looked clean of water, although it did seem a
little thin- I'm wondering if I got gas into my oil. Any idea of the
odds? Should I immediately change the oil? My rings are good- I had dry
compression of at least 120 lbs in all cylinders prior to my fun outing
which resulted in me getting a tow back to the dock so I'm hoping rather
than leaking fuel into my oil my cyliders just pumped the fuel out the
exhaust port.

A question- the heat pipe look welded at the manifold. Suggestions for
repair? JBWeld?

thanks guys,
Chris



chris wrote:

I'm stumped- I recently reconditioned a 1981 wellcraft 180 bowrider with
a straight 6 GM / mercruiser 250 c.i. motor and pre-alpha outdrive. I
put her into the water and she ran fine for about 15 minutes, then
burped on me at high speed / 2500 rpm- a loss of rpm/power then it would
come back up. Then about 30 minutes in, I was running at lower speed and
she died. I could fire her back up, but then the issue kept getting
worse- it would die more often, at progressively lower rpm, before
finally I couldn't get her to start at all. If I let her sit for a
while, I could eventually get her to start, but she'd eventually stumble
and die. I had to get a tow in which was damn embarrassing, but I
digress...

Carb is a 2 barrel rochester, and the arrangement has the fuel pump on
one side of the motor, a metal fuel line up over the valve cover to the
carb on the other side. When I would crank her, for about 2 seconds
afterwards I could hear a hiss that sounded like it was coming from
either the manifold/block gasket area or the carb/manifold gasket area.
I can't tell you if it's a normal sound b/c it was my first day out in
this boat.

I also noticed after getting towed to the dock (a good 30 minute
process) that I was leaking something into the lake - oil or gas. Not
good. Bilge was completely dry.

I need help to narrow down my search. My thoughts are that -
1) the leak and the non-starting are two different issues, and that I
have an outdrive leak somewhere and a fuel starvation issue somewhere.

or the 2 are related and either:
1) I flooded the engine and the gas was leaking out the exhaust into the
water slowly
or
2) manifold/block gasket leak, allowing water into the exhaust header. I
don't know the symptoms of hydraulic lock, other than I assume I would
be able to hear the motor sound different-
knocking/chattering/pinging... I hear none of that. Also the motor
hadn't run for a good 30 minutes so I don't know how water could have
made it's way up the riser, to the block, entered the block throught the
exhaust ports, and then trickled out to the exhaust to get back into the
water 30 minutes after last running/starting.

If you have any ideas or can set me straight on things to try first, I'd
appreciate it. I'm going to get to work tomorrow trying to cross things
it could be off my list...

Chris