396MY - Starboard engine shuts down - no reason

[TomO]

Hi. My name is Tom. I have a 396MY with Merc 8.1 gas engines. I have been dealing with an issue of stalling out on the starboard engine. I will give you the details. The engines starboard and port, after having be warmed up, once under load and approximately 1/2 hour to an hour underway, the starboard engine stalls out.
After cooling down for approximately 20 to 30 minutes, the engine will be able to be restarted. This has happened on multiple occasions. The boat cannot be trusted.

I have had the manifolds changed, the risers changed, all belts replaced, oil changed, etc, etc. It seems to be electrical, but we can’t understand what it is. Further, we had the computer control module from the starboard engine switched to the starboard side. The same problem happened again on the starboard engine.
We had the computer attached to the engines, hoping to see an error code getting thrown. No error code is displayed.

Has anyone heard of something like this? Any idea what can cause this? If the boat sits running at idle it will not shut down, only when it is under load.

Any help, suggestions are most appreciated.

Thank you.

[bud37]

Welcome to the forum.....sorry to hear about this, ....Has your guy checked the anti-siphon valve at the tank outlet, where the fuel feed hose exits the tank ??

[TomO]

Bud -

Thanks for the welcome.

I am not sure that they have, so I will pass this info along.
We have been dealing with this issue and it is getting everyone crazy.

Any other info I can pass along is really appreciated

Appreciate it,
Tom

[mjk1040]

Have all the fuel filters been changed or checked? Fuel lines checked for deterioration? The multi ignition plug been checked for corrosion and tightness. If in question, wire tie the plug together. Recently saw a coil to distributor wire arch across to one of the terminals causing stall out. Appeared coil cone was cracked. Fuel line or supply issues could be diagnosed by putting in an alternate fuel supply from a boat tank. Hope you find it soon. Season to short for this!

[tomschauer]

the 2001 mercs should have a "cool fuel" system. The fuel pump, fuel pressure regulator and a very fine fuel filter are in a "box" on the starboard side of the engine I believe.
When you say it stalls out, are you running at a decent rpm and it just shuts off hard, or does it slowly lose rpm and then shut off?

[pepmyster]

When it shuts down, when you turn off the key and then back on do you get the double beep sayinying it ready to start or do you get no beep? This was happening to mine, VP's 8.1. See my posts.
viewtopic.php?f=8&t=3583#p23866
For me at the end , I found the fire boy relay box under the dash defective causeing a no start.

[TomO]

The engine loses rpms, will not respond to throttle then dies. Like it is gas starved. After it cools it will restart, but it can take a half hour, or 45 minutes.

[TomO]

I also should have mentioned, this is a keyless start. It has a keypad.
The stalling can happen at random times. Last year we were running from Cape May to Atlantic City - about two to two and a half hour run, and it stalled out about two hours into the trip. Another time we were running to Ocean City, MD across the Delaware Bay, and about 45 minutes into the trip we had the same problem. Another time going to Lewis, DE we had the same issue. About an hour or so into the trip. It is driving us crazy. We thought it was the fuel, then we thought the filters, impellers, etc, but the problem keeps coming back. Nothing shows up on the computer when connected to the engine, no error codes.
Any other thoughts or suggestions are much appreciated. I am sending all the info to the boat yard where the mechanic has been trying to this thing figured out.
We actually had the boat getting ready to launch four times in the last three days, let it sit idling for an hour or so, both engines were purring, no signs of trouble. Once underway and under load, the nightmare happens. Never know when it will happen either. We got out front in AC running it down the beach to Cape May and it shut down.
Thanks everyone.

[bud37]

Lets see what your guy says about the anti-syphon......but there was an issue with some cool fuel pumps that had paint flaking and plugged cooling channels.....now your mechanic may know about this, I believe it to be common at this point, there was a fix....easy to find info online.......I am just not sure whether this issue applies to your engine combo and year though, I am sure he will know as there were some different versions over the years.

[Cooler]

TomO - Several boaters in our area had symptoms similar to yours. Mechanics were stumped at what was causing the issue because it seemed electrical, but acted like fuel issues. Did not appear on any diagnostic error codes. Turned out to be fuel injectors getting plugged up. Are you burning gas with ethanol? The ethanol creates a varnish like situation in the injector, and does not allow enough fuel, or the proper cone of fuel to be delivered. If that is the issue, the injectors can be cleaned or rebuilt for a lot less than replace. The other similarity is this issue is really prevalent in the 1999 to 2002 model years. Most repairs also needed the ignition module and coil replaced after the injectors were taken care of. Hope this helps. It took a friend of mine 2 seasons to find this out. The condition started out similar to yours, and deteriorated over time to the point where the impacted engine would not stay running even at idle. er