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Need some help with GT-40 problem

K

KIX

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I have a 2006 PCM, GT-40 EFI engine in an older Shamrock. Although the engine is an '06 it only has about 30 hours on it. It's been running perfectly until about a week ago. It starts and idles fine. Sometimes at around 3200 - 3500 RPM the engine will momentarily shut off. It's as though someone turned the key off then right back on. Other than that issue it runs perfectly. When this happens the gauges do not go to the ignition off position. Since the symptom is like ignition shut off I cleaned the connections on the ignition switch although it didn't look corroded. I also used electronic cleaner. This effort ad no effect on the problem.

Any suggestions of where to look for the problem will be most appreciated.

KIX
 
check the engine wiring harness connector, too. From there, I'd suspect the relays and sockets. Ignition coil is another possibility.

Depending upon how much older the boat is, the ignition switch (internally) could be failing. If the "miss" event occurs with sudden force on the hull, that's worth checking into.
 
Thanks Mako. I was talking to a 'gearhead" buddy last night and he suggested that it could be a fuel problem. His thoughts are that if a fuel filter is restricting flow then it could cause a motor shut down. Even for only a second, which is what it's doing.
So today I removed the water separator - fuel filter metal bowl and filter. I get the replacement filter cartridge tomorrow and can then test to see if this fixed it. In any case it was definitely time to change the filter.
My buddy's advice is check the filter very often especially if one is using gasoline with ethanol. I have been using gas containing ethanol but I'm not going to anymore. The gas without ethanol is more expensive but not that much more.

KIX
 
It is good that you have an economical choice - it doesn't exist around here.

My experience is electrical issues are usually have very 'short durations' and fuel issues are 'longer'. I had one exception - that was a cracked heat exchanger that would 'piss' on the ignition coil. Those 'momentary' drop outs fall into the 'short' class.
 
I think I have solved the problem. I got the new filter today and got it installed. had some trouble restarting the engine but as it turns out I needed to fill the separator bowl before install. Got that done and it runs. My neighbor was out of town so I didn't want to take it for a run on the river in case it shut down. If it had shut off out in the river so telling how long I would have floated around waiting on a tow back to the boathouse. I did run it in gear and at about 1200 rpm for about 15 minutes on the lift just hanging in the water. Seemed to run fine but the real test will be when I can get out on the river and run it at speed. Hope to have that chance this weekend.
Thanks for your suggestions.
 
If you think that did it, I'd be inclined to say you had a little water in the fuel. That can cause those momentary drops where a restriction would induce a major sustained rpm drop.

You may want to get a few extra filters and carry at least one on the boat. If the issue was water and the ethanol was the root cause, it may recur until you have filled the tank several times.
 
makomark said:
If you think that did it, I'd be inclined to say you had a little water in the fuel. That can cause those momentary drops where a restriction would induce a major sustained rpm drop.

You may want to get a few extra filters and carry at least one on the boat. If the issue was water and the ethanol was the root cause, it may recur until you have filled the tank several times.
Click to expand...

My first test run after the filter change had to be abbreviated but it did not "miss". I'm going to try it again today for a longer period. We'll see what happens and I'll report back. KIX
 
KIX said:
My first test run after the filter change had to be abbreviated but it did not "miss". I'm going to try it again today for a longer period. We'll see what happens and I'll report back. KIX
Click to expand...

It was pretty windy today so I decided not to go out and test it. If I had to be towed back in it would have been a real PITA with the chop on the water.

So, I decided to siphon out all the gas with ethanol that was in the tanks. Got that done then put about 12 gals on non-ethanol gas back in each tank. It was still to rough to go test it so maybe tomorrow.
 
OK, here's my final update of the problem. At least I hope it's the final update.

Since my last post I've been able to run the boat for a total of maybe 45 minutes at 3200 rpm. No engine miss or shut down at all.

I guessing it was fuel with ethanol. I've got all that fuel out now and using non-ethanol fuel. Keeping my fingers crossed.
KIX
 
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