Sudden engine shutdown

[azazzera]

I guess it was only a matter of time. Engine has been running flawlessly since rebuild two years ago. Today I changed my antifreeze. Refilled the exchanger and started the engine. It started clean as it has every other time. Maybe an extra revolution or two to start but very quick no sputtering. Pressure came up quickly. Water out the stern with same volume as other runs. About 30-45 seconds the engine stoped as if ignition was shut off. 4 or 5 attempts to restart with different choke settings had no effect. Only cranked. Did not seem like engine was going to start. So I started the diagnostics. 11.6 or so volts at coil. Had electricity to each plug with use of commercial tester that shows spark in window. Took each plug off and did compression test with finger test over plug hole. Now with all that cranking the carb was leaking gas. Took hose off carb and cranked engine. Strong gas flow into container. So I'm thinking some sort of clogged carb orifice or jet. IDE jet maybe. I closed ide mixture and opened one turn. Still no start. I then closed it and opened one full turn. It started but again stopped as befor quickly. I then closed ide mixture again and opened 1/4. It started and stayed. I had to shut it down because I felt the engine was ever heating due to maybe not enough coolant. Ran out of time to fix or run down over heat situation.

So my main question is is it likely that my shut down and no start was a clogged or restricted something in the carb. Would that have given me such an abrupt and quick shutdown?

[ndutton]

What caught my eye

45 seconds to a minute or so is about the time it takes to consume the fuel in the carburetor bowl without replenishment. I suspect you're not getting fuel supplied to the carburetor for whatever reason.

[azazzera]

So I guess I'm looking at a carb cleaning. Could the bowl still be filling but not get any further? I had significant leaking from carb of gas. Ide jet maybe transiently plugged? It may have been flooded with all that cranking in between starts. I looked at each plug and they looked wet and smelled of gas. I did drain bowl and removed the main jet plug. I anticipated the amount of fuel I got out of bowl drain but is it normal for 5 or so cc to drain from main jet plug?

[JOHN COOKSON]

If you have an electronic fuel pump short or bypass the OPSS then try to start. You can fill the carb bowel by temporally by connecting the fuel pump to a live un switched hot point - the battery works well. This will reduce the cranking a bit.

TRUE GRIT

[Nauti Buoy]

Similar engine shut down

I have been afflicted by similar symptoms. When the engine stops it's as though someone has switched the ignition off. No sputtering, etc.

We installed a rebuilt engine from Moyer 2 seasons ago. At first I was convinced it was anything but fuel because of the way the engine shut down and I track fuel consumption in excruciating detail. (Aircraft pilot for 35+ years, no fuel gauge and unable to dip the tank because of a goose neck in the filler)

22 gal tank, estimating 3/4 gal per hour fuel burn and 4 to 5 hrs in to a full tank when this problem occurs. Even if was burning a gallon per hour I would still have roughly 1/2 tank. I assumed the worst the first time and thought just maybe I miscalculated and ran out of fuel. The tank only accepted a little over 6.5 gallons upon refueling the first time. I have not refilled the tank yet this last time as I'm hoping to disassemble some of the tank to look for a defective dip tube or debris.

I have a Racor filter and a polishing filter installed just before the carburetor. Both have been inspected and are up to par with no apparent water contamination. I do have a copper fuel line and have considered replacing it with a steel one but don't know if that's worth the effort just yet. All the normal electrical tests check ok as well.

If the dip tube and debris are not issues I will start over with all electrical connectors on the engine.

[JOHN COOKSON]

Please, please get a fuel pressure gauge after the fuel pump.
Also if you have an electronic fuel pump try shorting across or bypassing the OPSS.

TRUE GRIT

Edit: Try running off an auxiliary tank. This will tell you if the problem is with the tank or after the tank.

[azazzera]

Plan on installing fuel pressure gauge as soon as I get back to boat. Needed to wait for 5/16 barb fitting as the one I originally purchased was for 3/8. I will put the gauge directly before the carb thereby looking at pressure right before carb.

I've determined for now my difficulty was possible flooding from too much choke for too long. I'm still going to take carb off at end off season and clean. I know I run lean because I have to have some choke in while above 1500 rpm. It runs much smoother with choke. I have a mechanical pump.

[JOHN COOKSON]

Plan on installing fuel pressure gauge as soon as I get back to boat. Needed to wait for 5/16 barb fitting as the one I originally purchased was for 3/8. I will put the gauge directly before the carb thereby looking at pressure right before carb.

I've determined for now my difficulty was possible flooding from too much choke for too long. I'm still going to take carb off at end off season and clean. I know I run lean because I have to have some choke in while above 1500 rpm. It runs much smoother with choke. I have a mechanical pump.

My response in post #6 was directed to NautiBuoy. He or she needs to start their own thread.
I don't see how over choking would cause an abrupt shut down like you mentioned in post #1. Usually over choking causes the engine to run poorly before shutting down.
It does seem you are running a bit lean. Sounds like you are in for a carb over haul. Air leaks will cause the same symptoms.....

TRUE GRIT