2004 Mercruiser 4.3l (Gen+) #0W011342 stall when warmed up

C

ckuhtz

New Member
Oct 6, 2019
16
Boat Info
185 Sport
Engines
262 Mercruiser w/ Alpha I Gen 2 Drive
Hey guys,

I have been chasing a gremlin since the end of last season and could use a pointer or two for the cause of this issue. Going to try to give you as much info as I can, including a video of two occurrences.

First time of the season that I started the boat today. It would not fire first try by just turning the key on idle as expected. Two pumps with throttle lever and the engine started right up as expected. Warmed the engine up for several minutes. During that time ran the engine at idle, 2k rpm, 3k rpm 4k rpm, with no issues. Ran like a charm.

Then once warmed up, the symptoms start. It stalls about ~15 seconds after starting pretty consistently when in this state.

I recorded two instances in my driveway, one with throttle at idle and one advanced to the first "detent" (~2k rpm). The throttle wasn't touched after being set before the stall. The key was turned back to ignition, then start, and was not completely removed.

Video of two start attempts ending in stalls:


At the end of last season, I saw the behavior also manifest as stalling at 3-4k rpm for several minutes and then being almost impossible to refire. Spraying carb cleaner into the carb, I could sometimes get it to light, but then it would stall. Eventually, it'd refire, and I could limp it back to the dock.

No other symptoms. Fuel filters (canister and then inline filter) have been replaced several times with no change. Fuel is clean non-ethanol with stabil marine. Battery charge is good (new battery on maintainer). The plugs are newish. The Spark arrestor is clean. Correct fresh oil. Last year, the oil pressure fuel shut-off switch was replaced with a genuine one, with no change and as a no-regrets preventative.

The engine has 175 hours and is unmolested to the best of my knowledge.

Thanks,
Christian
 
Taking a few tries to start up after it's long winter nap is pretty normal since it's a carb'd engine.

Try taking the gas cap off and see if that makes things better. If no better, plumb a gas can direct to the fuel/water separator and eliminate the boat-side of the fuel system.
 
Please read what I wrote again and watch the video. This isn’t about first startup after winter or a fuel issue.
 
I don’t know which. How would I establish the cause of the stall?
 
ckuhtz said:
. . . This isn’t about first startup . . . or a fuel issue.
Click to expand...
Am curious when and how you determined that later part. My advice would've been the same as Lazy Dave's.
If you know it's not gas related, have you done any checking on the ignition system after it's stalled and unable to start?

The thread that wouldn't end, went for ages largely because the OP claimed what ended up being the problem, couldn't possibly be the problem. I'm sure I'm not the only one that doesn't want to see you do that to yourself.
 
ckuhtz said:
I don’t know which. How would I establish the cause of the stall?
Click to expand...
Were I you, I would start with Lazy Dave's first assessment. It is the easiest, most cost effective place to start and could either solve the problem or point to it.

As Mitch implied, you are lacking gas or spark. Got to start somewhere.
 
you guys are killing me ;-) yes, I know air/fuel/spark = boom.

For grins, I took flame arrestor off and squirted carb cleaner into the barrel(s) when the stall occurs which made the engine run for a few seconds longer depending on how great my manual fuel injector timing was.

In other words, we have spark but not enough fuel.

Time to take more things apart.
 
techmitch said:
Monitor the fuel pressure before and when the problem occurs.
Click to expand...

Thanks, yes, but without the 91-18078 on hand or something to rig up from parts and hose, it isn't going to happen on the boat. I pulled the pump and will test it on the bench tomorrow.
 
ckuhtz said:
Thanks, yes, but without the 91-18078 on hand or something to rig up from parts and hose, it isn't going to happen on the boat. I pulled the pump and will test it on the bench tomorrow.
Click to expand...

And I've pulled the barb with the check valve on the tank fitting, which also appears to be in good order. Not stuck or gummed up etc.
 
I think you need to rig up a portable tank - just need a section of fuel hose and a portable can. I do this every year to fog my engine. If it runs fine this way, you have isolated it to a fuel supply problem between the fuel pump and tank. I had a similar issue with my 4.3, it would startup fine and after a min or so it would just stall. My issue ended up being the anti-siphon valve, it looked fine, but it wasn't. On an older boat the rubber fuel line, anti-siphon valve, tank pickup, even the hose clamps losening and sucking air can all be suspect with fuel problems - especially if you have been running ethanol fuel. If it doesn't run on the portable tank, then move up the line, but before you tear into the fuel pump, check the inlet filter, small screen that is in-line with the fuel line where it connects to the carburetor. Eliminate the simple things first - in 30yrs and 1000's of hours of boating I have only replaced one fuel pump - I have replaced numerous anti-siphon valves, fuel hoses, filters etc.
 
It sounds like it is running out of gas in the video. With a carb the fuel that you pumped in would probably last that long and then it would burn off.

As to the restart....I takes a few moments for it to restart which again seems fuel related. A failing electrical fuel pump could explain the symptoms as well as bad fuel.

I'm with the others but I would start with checking the fuel pressure on the boat.....not bench testing it. If fuel pressure is okay then I would use a separate tank with fresh fuel to feed it. If it isn't one of those two things....then it points to the carb since you can keep it running using "human based fuel injection".

Was the carb rebuilt at some point?

Thanks for posting the engine serial number......it makes it a lot easier to see what you have.
 
The root cause was a failing oil pressure safety switch (<1yr old) that intermittently/occasionally worked correctly. The part was replaced late last year with a genuine Mercury part from the local dealer. Confirmed by shorting the connector to bypass the switch and energize the fuel pump with a Dupont connector male-male cable (paper clip would've worked as well).

When the starter cranks the engine, the starter harness provides power to the fuel pump to bridge the gap until the engine makes pressure to close the switch. This is enough to supply the carb with a small amount of fuel to run. Once the carburetor is out of fuel, the engine shuts down.

The ~15s duration should've been a clue that this oil pressure safety switch was a candidate.
 
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