LKNCOBALT

That's right.... You read this correctly. I could not turn my port side engine off! All the years I've tried to get engines to run in boats, motorcycles, cars.... I've never had one I couldn't shut off!

Today I was at the marina with my 02 fountain 29 fever. It has twin 350 mag mpi fuel injected engines. Lately the port side engine has had trouble starting when cold. It turns over for a few seconds and then the starter finally stops and a puff of white smoke comes out of the flame arrestor. After several attempts I gave up and started the starboard engine. It lit right up. I tried the port side again and it fired up an idled perfectly. Just for good measure I wanted to cut off both engines and make sure they re started with no problem before I left the dock. I turned off the starboard engine and then turned off the Key of the port motor and it kept running!!!!

A bit astonished, I cycled the key again, and it did nothing... Engine still running.

I then cut off both battery switches to off, and again it did nothing... Engine still running.

Next I pulled the emergency cut off switch. Nada! Port engine still running.

At this point I was at a loss of ideas. Not to mention I had 140 gallons of fuel, so this thing was going to run all week at this pace!

Oh yea! Fuel.... The engine can't run without that. I cut the fuel supply lever off that fountain was so smart to include, and waited 5 minutes for the port engine to run out of gas.

I checked the ground and positive cables, all the battery connections, and the ignition switch connections on the dash. Nothing was loose. Wtf?

So I really have 2 issues.

1). A port engine not wanting to start cold, and puffing smoke out of the flame arrestor.

2). A possessed port engine that won't turn off by the key or any kill switch.

HELP PLEASE!!!!

FIXX

iTrader: (2)

check the starter solenoid to make sure its not staying engaged..their is 2 wires that go to the solenoid one is start (s) and the other is ignotion (i) on the solenoid..the i feeds power back to the ignition module so it fires.. might also want to check the slave solenoid or the starter as well..

dereknkathy

also the power fed from the alternator. if it is crossed to ignition, it will do this.

Cole2534

iTrader: (1)

Bump- mine just did this as well. Pulled fuel pump relay to kill it.

Would the above failures prevent the kill switch from working?

Any other culprits to check?

Cole2534

iTrader: (1)

Got it isolated to the alternator. When I unplug it with the key off the engine dies. Do I need a new plug?

BUP

iTrader: (9)

I would take the ignition switch out of the mix as bypassing it both ways - for starting and turning off the engine - just to make sure its not that because it can be. Next is the MPR = main power relay bad or even the fuel pump power relay bad. When this motor is running and can not be turned off just asking what is voltage at the battery and backside of the alternator ? Does your kill switch work to turn off the engines - with a pulled kill switch you should not even have power to the fuel pump - Just saying ?

What are the serial # of the engine(s) - just because you have a 350 mpi and even a certain year model does not mean that they are wired the same thru the OEM. Next are your engines stock and is the wiring harness stock ? If not what do you have ?

Next a few years back - long story 2 different techs had 2 different problems with believe it or not Mercruiser 350 MPI with ECM 555.

the first problem for tech number 1 - was when you turned the battery selector switch (Perko battery switch) to the on or all position the engine would start all by itself - not even a key in ignition - the engine would start all by itself when battery power was applied

next problem for tech # 2 was the engine would not turn off at the key switch - most everyone pointed to bad ignition switch to faulty relays to the alternator itself. Both problems were the ECM's faulty and wiring. I will pat myself on the back because I was the one that figured it out for both tech's. Just saying and not saying this is your fault but with these ECM's controlled engines - you can never rule anything out.

LKNCOBALT

When this happened to me, the fix was a new ECM. Had to take it to a local Mercury dealer and they hooked up to the computer and were able to diagnose it. Not a cheap fix like the ignition switch I had hoped was the issue. The repair facility also found our that the distributor on both motors were out of time from whoever the previous owner had change the plugs/wires/rotor. Boat has run incredible ever since we got the corrections made. Good luck!

BUP

iTrader: (9)

Thanks and BINGO the ECM was the problem as I mentioned in the post above. Also if your engine is a ECM 555 or PCM 555 computer controlled - THE TIMING is not adjustable nor the distributor controls any form of when to deliver spark. It only delivers the spark to the sparks plugs. Its all controlled events by the ECM / PCM, These distributors really are not distributors persay - they are called HVS = High Voltage Switch.

They need to be properly phased / clocked when installed or rotated for any reason. That's the deal with the HVS that many call the so called distributor. It does have a flat cap & rotor, shaft though and of course spark plugs wires attached along with a coil wire.

BUP

iTrader: (9)

Forgot never turn your battery selector switch while the engine is running - this is a sure way of knocking out relay(s) or the alternator or the ECM / PCM itself. Just saying. ECM controlled need enough proper voltage and constant steady voltage. They do not do very well with low voltage, excessive voltage or any voltage spikes. They hate vibration, moisture and excessive heat to.

Cole2534

iTrader: (1)

I'll look at that later. After it died when I disconnected the alternator I assumed I'd found the issue. I'll check about the voltage and kill switch tonight.