3.0 Mercruiser stalls when warm

[strayliner]

I just got a 2001 Bayliner 175 Capri with a 3.0 Mercruiser inline four cylinder and Alpha One outdrive. It starts and seems to run fine for 15-20 minutes. It then pops/backfires thru the carb and stalls. It starts again almost immediately but will not run above idle. While idling back to the dock it will stall again every couple of minutes.

 

[dubs283]

Re: 3.0 Mercruiser stalls when warm

is the vent line on the fuel tank clear/free of kinks??

when was the last tune-up/carb adjustment??

 

[strayliner]

Re: 3.0 Mercruiser stalls when warm

Vent line looks fine, I disconnected it at the tank and blew thru it, didn't seem to have any obstruction. I also checked fuel filter in carb/ fuel connection which looked fine. Just got boat over Memorial Day and do not know when the last tune-up / carb adjustment was done.

 

[dubs283]

Re: 3.0 Mercruiser stalls when warm

there is a fuel filter in the pump as well, port side of engine

maybe its time for a FULL tune-up - its recommended every two years, some even say annually

 

[strayliner]

Re: 3.0 Mercruiser stalls when warm

Thanks . . . I'll check the filter in the pump next. By full tune-up you mean plugs, wires, cap, rotor, filters? I did change oil and lower unit oil. Also cleaned flame arrestor.

 

[dubs283]

Re: 3.0 Mercruiser stalls when warm

By full tune-up you mean plugs, wires, cap, rotor, filters?

yep, and...

spray carb and choke with spray cleaner and adjust idle settings, and points if conventional ignition, but 2001 you should have electronic

 

[Pete104]

Re: 3.0 Mercruiser stalls when warm

Along with a tune-up. Plan on a carb rebuild!

 

[strayliner]

Re: 3.0 Mercruiser stalls when warm

Over the weekend I changed the fuel filter in the fuel pump and sprayed carb cleaner thru the carb and choke while it was running. Same problem. I used a spark tester (light between distributer and spark plug) and the spark seemed to erratic before it went out and the engine quit. After boat sits for 20 minutes it will start and run fine for 10-15 minutes.

I guess it's time for that tune up and carb rebuild!

 

[Desertsky]

Re: 3.0 Mercruiser stalls when warm

Sounds like it might be a bad coil. Some of them get intermittent when hot and start to break down (technical term!) when pushed to higher RPMS or more compression. Same can be true for other parts if it has electronic ignition.

 

[jonirish]

Re: 3.0 Mercruiser stalls when warm

Bad Fuel in tank

 

[CobiaXL]

Re: 3.0 Mercruiser stalls when warm

Is your choke fully open when it dies?

 

[strayliner]

Re: 3.0 Mercruiser stalls when warm

I siphoned some fuel from the bottom of the tank (thru vent tube opening at tank) into a glass jar. It looked like gas, smelled like gas, anything else I should be looking for? It had 1/2 tank in it all winter. I filled the other half when I got it and added two bottles of Heet. It's a 23 gallon tank, what would I do with 23 gallons of bad fuel?

 

[strayliner]

Re: 3.0 Mercruiser stalls when warm

The choke is open while it's running and is open when the engine re-fires, so I'm assuming it's open when it dies.

 

[CobiaXL]

Re: 3.0 Mercruiser stalls when warm

Ignition module heating up?Or coil if applicable.

 

[bds85466]

Re: 3.0 Mercruiser stalls when warm

I used a spark tester (light between distributer and spark plug) and the spark seemed to erratic before it went out and the engine quit. After boat sits for 20 minutes it will start and run fine for 10-15 minutes.

I think this is a crucial clue.

Is there noticeable stalling/hesitation/shaking/misfiring?

Something is causing you to have spark problems. Possibly as the engine warms up. Sounds like after it cools down, the cycle resets. An expert on here could tell you better, but you might want to work your way through electrical troubleshooting through the coil and distributor, etc.

 

[strayliner]

Re: 3.0 Mercruiser stalls when warm

Yes, there is a little misfire / shaking / hesitation before it quits. I put in a new coil yesterday, same problem. I gguess I'll try the ignition module / distributor next.

 

[dubs283]

Re: 3.0 Mercruiser stalls when warm

in an earlier post you mentioned using a spark tester between the distributor and plug while running and the spark seemed erratic - this could be due to the engine misfiring caused by some other problem, e.g. fuel delivery

you need to check for spark at the coil tower - put your spark tester between the coil tower and ground and crank the engine over and look for spark, you especially need to test here when the engine dies on you

you also mentioned you would be doing a tune-up and carb adjustment - have you done this yet?? or even looked at the plugs/under the cap??

 

[jwe14]

Re: 3.0 Mercruiser stalls when warm

Had the same problem. The hint to my problem was that the backfiring started after I replaced a bad slave solenoid. What it turned out to be was a bad 55 amp fuse (attached to the starter solenoid)..$28 fix. I must have crossed the wires when I was monkeying with the solenoids. You can tell if the fuse is bad by the color. A good fuse should look yellowish while a bad one is black.....and btw..they don't look like fuses so don't be fooled. It is the hanging piece attached to your starter solenoid. Even though I had what I thought was continuity..the fuse was bad and causing the backfiring/stalling.

My manual for my 3.0L alpha one says in the troubleshooting section that if engine is backfiring it is one of four things.

1.bad gas
2. carburetor
3. Ignition system
4. air intakes

If your boat was running fine before this problem, you can start eliminating some of these items. bad gas is usually seen from the first time you start the engine for the year. carburetor problems seem to start out and slowly get worse...same as intakes. If it is an 'all of a sudden' type problem..it's probably electrical. I'd even check all the + and - leads for corrosion or see if they have come a little loose and are arching. A wire brush, contact spray, and new connections can solve some hard to diagnose problems.

 

[bds85466]

Re: 3.0 Mercruiser stalls when warm

... this could be due to the engine misfiring caused by some other problem, e.g. fuel delivery

absolutely. you could be having delivery problems (since your filter is new, it'd probably be more local to your carb), causing sputtering, which could result in erratic spark in that location. as dubs implied though, a good way to find if it's spark is to dig in at that location.

 

[strayliner]

Re: 3.0 Mercruiser stalls when warm

Okay . . .
new coil, plugs, wires, cap, rotor, fuel filters, pickup tube screen, anti siphon valve, fuse block on starter solenoid, adjusted carb, cleaned carb, checked vent tube . . . boat has never run better. For 10 minutes! Then dies. A few minutes later it will run again, but only for a few minutes. What am I missing?!? I'm going to try a second gas can with a primer bulb attached before the fuel pump. My guess is if it runs while I pump the bulb, I need a new pump. Correct?