----------------
Another idea I wanted to run past all of you: what do you think if it's
something related to my oil pressure being messed up, and cutting off
the fuel intake line from entering the carb? How does one easily test
this ? What test equipment do I need?
----------------
One last idea (got this from the manual last night)

If an engine running problem is diagnosed as fuel starvation, check the
anti-siphon valve. If
the valve is stuck or clogged, change or replace it while the engine is
shut down.
· NEVER run the engine with the anti-siphon valve removed, except in
an emergency.

Anti-siphon Valve
· Your boat is equipped with an anti-siphon valve, which is an
integral part of fuel system.
· The valve is located at the point where the fuel feed line attaches
to the fuel tank.
· The valve is spring loaded and is opened by fuel pump vacuum.
· This valve will prevent fuel from siphoning from the tank in the
event of a fuel line rupture.

-----------------

Regarding the anti-siphon valve.. would ANY fuel be coming out if this
were the issue, or could this activate after 10-20 seconds?? That
would be insane if that was the issue!!!

kyle wrote:
fuel pump has been replaced .. it gushes fuel out the line when removed
from the carb. intake and i'm turning the key over...

how could it be a gas vent thing? where is the vent, anyways.. is it
between the gas tank and the fuel filter?

don't know if i mentioned but it is an I/O.

Del Cecchi wrote:
"kyle" wrote in message
oups.com...
hi all,

i am at my wits end over this 2003 bayliner 5.0L merc.

here is the symptom:

give it some warmpup throttle action, turn key on, she cranks
beautifully. no smoke. no roughness.

10-20 seconds later, she instantly cuts off.

so.. youre thinking.. it must be a fuel thing, right?

i started small: i replaced the fuel filter. same result.

a little larger: i replaced the fuel pump (it's an electronic fuel
pump, we tested with it unhooked from carb and it was a weak stream..
after replacement she was peein' strong). same result.

a little larger: i replaced the ignition coil. same result.

a little larger: i rebuilt the carb. at this point, she showed
promise. we took her out on the lake for about an hour and she ran
beautifully!! i let her sit for a week .. then bam, same damn result
as before!! 10-20 second purr then cut off.

so i said damn it, let's look at the carb again. no fuel is getting
down in the manifold after the initial warmup throttle action!! so
figured something is messed up with carb.. went down and bought a fresh
rebuilt carb.. last night.. put it on.. same result! and i still
don't see fuel dropping into the 2 barrels after crankup. it does
make a noise like it's spraying air or something at least. but it was
somewhat dark when i was observing it this time...

the guy i bought the boat from had done a lot of wiring himself (mp3
player, gps..) .. could it be some electrical shorting after 10-20
seconds or would it only be a startup thing?

my next order of business is going at it from the distributor system.
maybe the distributor chip is bad? distributor cap? what else could it
be!! man this is driving me nuts. that engine is practically new at
this point!!

also, what do you think about some crap in the fuel? i filled the damn
tank up from about 3 gallons.. but what if there is dirt or water or
something in the tank and it keeps suckin' up dirt? should i drain the
40 gallon tank.. and clean the tank somehow (never done that.. whats
the best way to do it?) give that a shot? the one thing that leads me
to believe it isnt the tank is that when i warmup throttle action it
pushes fuel down the manifold so the fuel filter seems to be fine?
maybe just not fine all the time?

any suggestions would be great. i've had it in and out of the shop and
they had it fixed at one point but then 1 week later it died again
(without me doing anything in between then).

i'm tempted to sell the boat, get something else, but i am in it $12K
and who is going to buy an '03 bayliner 21.5ft that doesnt run for
anywhere near that?? best bet is to get it running, then sell it, i
guess, or maybe keep it since ive grown attached :

thank you so much for your time reading this,


kyle

If it were a car I would start wondering about fuel pump. Or vent on the
gas tank. If the bowl on the carb is dry when it dies then no gas
getting to motor. problem is fuel pump, gas line, tank etc.