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SOLVED Cutting Out-07 MerCruiser BLACK SCORPION 350 MAG MPI

 
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joelgriffiths
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PostPosted: Mar 22, 2016 8:07 am    Post subject: SOLVED Cutting Out-07 MerCruiser BLACK SCORPION 350 MAG MPI Reply with quote

Hi guys:

I've been struggling with my 2008 Sanger this season and I'm hoping somebody can point me in the right direction. Here are the symptoms:

1) Engine will quickly turn off and on at idle, at speed, during initial acceleration, and under load at wakeboard speeds (with and without ballast). I haven't seen the problem at wakesurf speeds (9.5-10) with full ballast, but I've probably just been lucky.
2) It doesn't sputter. It doesn't slow down and stall like it's starving for fuel. It just shuts off. At idle you can watch the RPM needle suddenly drop to 0, the boat will beep, then the motor recovers and goes back to normal.
3) At speed, it drops about 1K, beeps, and goes back to normal; it recovers before the needle can fall that far.
4) It usually takes about a second for the boat to die and recover. It's quick.
5) It's extremely intermittent. Sometimes it will run without a single issue for 5-10 minutes and sometimes it will repeatedly turn off/on every 5 to 10 seconds.
6) It does stall at idle, occasionally, but it's been doing that since 2009.

Most recent maintenance:
1) New fuel filter
2) New impeller
3) New coil wire (last trip)
4) New cap/rotor
5) Engine Oil/Trans Fluid/V-Drive oil/Oil Filter
6) New plugs/wires (last season)

I've double checked all of the spark plug wires and I've reseated the rotor. I was especially suspicious of the coil wire because I hadn't changed it last year (the kit was missing the correct wire). I changed it last week; it didn't help.

Checking online, I couldn't find any completely similar problems. There are a lot of "engine stalls" posts, but nothing where the engine just shuts off briefly. Stalling is more of a sputter. In this case, the Tachometer looks like it's doing jumping jacks at idle (800 to 0 to 800 in about a second). When driving at 20-30MPH, the needle jumps from 3k to 2k to 3k. It would probably go to zero, but the engine recovers before before the needle falls that far.

Some online solutions to stalling I've seen:
1) Fuel pump
2) Wires/Plugs
3) Tachometer (don't know how this could CAUSE a stall)
4) Coil
5) Idle Air Valve
6) Ignition Sensor

When I go out next week, I'll take a code reader with me. In the meantime, does anybody have a best-guess for what might cause this?

I really appreciate any help.

Engine:
http://www.marineengine.com/parts/mercruiser-sterndrive-parts/black-scorpion-350-mag-mpi/0w690000-thru-0w698432


Last edited by joelgriffiths on Jun 21, 2016 1:48 pm; edited 1 time in total
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PostPosted: Mar 22, 2016 11:45 am    Post subject: Reply with quote

You have a lose connectoin.

I'd predominantly look at electrical plug connections, starter, engine grounds, ignition key switch etc....

Also relays, lose fuses in holders etc.

This could be very simple if you find it fast. Start at the battery terminals and move on from there.

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joelgriffiths
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Joined: 21 Mar 2016
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City: Irvine

PostPosted: Mar 22, 2016 9:50 pm    Post subject: Reply with quote

Thanks for the Feedback. I will check all the wiring the next time I'm there. I'm particularly interested in checking the ignition switch; I remember having problems with that in the past.

For future visitors, the wiring diagrams for most Mercruiser engines can be found here:
http://www.boatfix.com/merc/techbk/96/96hgd4.pdf

For my MIE 350 Magnum MPI Gen + Tournament Ski (Black Scorpion), the applicable pages are:
4D-16, 4D-22, 4D-26, 4D-30 to 4D-33

If I find the problem, I will be back. Thanks for the help.
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pet575
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PostPosted: Mar 23, 2016 6:42 am    Post subject: Reply with quote

Agreed on the loose connection. I'd start with every ignition-related ground wire you can find and check it to make sure it is tight and clear of any corrosion.
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joelgriffiths
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City: Irvine

PostPosted: Jun 21, 2016 1:45 pm    Post subject: Reply with quote

#### SOLUTION #####

Okay. For future reference since Googlng for "engine cutting out" kept bringing me back to this page.

The original problem seemed to go away after fiddling with some wires around the ignition switch, but it was replaced with another problem.

It started cutting out like it was starving for fuel under heavy load (ballast or high speed). It was different than the original problem and really seemed like a fuel system problem. To eliminate the most obvious "water in the fuel system" problem, I brought a container of gas and some tubing to feed into the fuel system and crawled in back to attach a line when I noticed that..

THE PUMP/COOLER KIT WAS UNPLUGGED

Yep. It was that simple. I actually don't know why it even ran, but it did.

Anyways, I'm leaving the information here just in case it could help somebody.

I appreciate all the help from you guys.
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