2002 350 MAG dies and may start

[statman]

Here is my frustrating story for the past three months. 310 Sundancer with 350 Mags.

The port engine started having problems with starting and keep running. Of course everything worked fine when the mechanic was there.

The engine starts and then may run two hours or two minutes. Then again it may not start after it died. Here are some scenarios.

1) Engine would start and idle, run for a couple minutes and die.

1a) I changed the water separator filter and the inline fuel filter.

2) Go out for a cruise at 3000 rpm for 30 minutes then engine died. Turns over but would not start. Tried for 15 minutes. Gave up, came back to the dock one engine for and hour. Then engine started up when at the dock.

3) Go out for an hour at 2000 rpm no problems. Sit in a cove for 7 hours. The engine would turn over but would not start (tried 20 minutes). Come home 10 miles on one engine, then port started at the doc.

3) Go out for a 3 hour cruise no problems.

4) Go out for 10 minute cruise no problem. Time to come back, runs for 5 minutes dies, will not stay running at all.

5) mechanic comes out when I'm not there, runs for an hour in the slip, no problems. Checked fuel pressure and all fuel pump connections, no problems.

6) OK, another weekend, same issues. Started engine checked all electrical connections no loose ones.

I have read threads about the AIC valve, but they discuss problems with idle. Will that valve cause problems at rpm?

Any other thoughts????

Thanks, Duane

 

[FamilyTime]

My IAC problem had no effect at idle, it was a partial failure that gave me problems at cruise or when slowing down or etc. I changed it out and the problem was fixed. I hate to throw money and parts at problems without knowing if it'll work or not, but it did for me in this case. Best of luck.

 

[douglee25]

Next time the engine won't start, try advancing the throttle to a higher rpm. If that lets your engine fire and stay running, I'd look to the IAC.

Doug

 

[flflatrate]

do you know which distributor you have? is the cap flat with 2 screws holding it down or are the wires on top with 4 screws holding it down. if its the 1 with 4 screws they did have allot of problems with the sensor in the distributor doing the same thing that you are speaking about.

 

[Blueone]

When the engine dies....are there any other electrical problems?

 

[statman]

I appreciate the input. It will be a couple weeks before I am back at the lake but will try your ideas.

I have not tried starting with the throttle for more RPM, but will.

Not sure about the distributor, but will check it out.

When the engine dies, I have not noticed any other electical problems. The one strange issue is the following. Once the engine dies, and I try to restart, the fuel pump seems to surge on and off. You know, normally when you give power to the start switch the pump will come on and build pressure then shut off until you start the motor. I have noticed when I have had problem starting the pump would build pressure, then go off, then on and off a few times more.

I spoke with my service department again. They believe that it leans toward a possible electrical short maybe in a ground.

Thanks for all the ideas!!

Duane

 

[Blueone]

Duane...reason I asked that question is Merc had a wide spread recall with the wiring from the alternator that was pinched between the dipstick tube and the block....vibration caused the casing on the wires to wear down and short....my current boat never had the recall done, I bought it used.....and that short caused me all kinds of problems before I thought of it...just something to check

 

[statman]

Blueone,

Thanks, I'll check that wire also. There is apparently a Mercury Marine service bulletin for the ground wire on the power steering cooler causing problems. I'll have lots of checking the next time at the lake.

Thanks

 

[raffles]

I had a somewhat similar issue where one engine was surging and then would cut out for no apparent reason, and then magically disappear and restart (sometimes). For me it turned out to be a bad relay and the fuel pump was intermittently getting power

Here is a link of the part (#16 in the schematic) – To eliminate this as a possibility, just swap the your relays from port to starboard and see what happens

http://www.perfprotech.com/store/as...(Mechanical-Throttle-and-Shift),11742-30.aspx

Good luck

 

[hack4alivin]

I had a somewhat similar issue where one engine was surging and then would cut out for no apparent reason, and then magically disappear and restart (sometimes). For me it turned out to be a bad relay and the fuel pump was intermittently getting power

Here is a link of the part (#16 in the schematic) – To eliminate this as a possibility, just swap the your relays from port to starboard and see what happens

http://www.perfprotech.com/store/as...(Mechanical-Throttle-and-Shift),11742-30.aspx

Good luck

+1

I had problems with my fuel pump relays as well on both engines. I would change the relays. Easy to do, they are mounted on top the engine, plug in style relays.