Gas Engine Cuts out at 24 mph and returns with a beep

[Michael Cooley]

Hello All.
I have an issue recently. I have only had the boat for about 5 months.
2006 340 Sundancer with twin Inboard 8.1 horizons.
While running at about 24 to 27 mph I lose power in both engines. This happens typically about an hour or two of running regardless of how long I have been on plane (combination idle speed then on plane then back to idle). Both RPM gauges fall like I turned off the engines and within a second or so I hear the ignition beep and power is returned. No rough running of any kind before or after. It usually takes another two to three hours to happen again. This has happened in relatively calm seas, and does not happen in rough seas thus far. It has happened only one time continuously (only 1 to two minutes between repeating) after running for 5 hours. Then again after 3 or 4 instances did not happen again for the rest of the day (3 additional hours). The following day it did not happen at all 6 hours of continuous running. So far it has happened with full, three quarter and half a tank of gas. I have not gone below just under half a tank of fuel. I have never had to restart the engines and never had to reduce power or have rough engine. No black smoke or other issues. Also I went to change the fuel/water separators and cannot find them. Does this model have the Racor filters or just the small secondary filters?
Any assistance would be helpful.

Michael
2006 340 Sundancer
Twin Inboard Mercruiser 8.1 Horizon

 

[PlayDate]

Michael,

Welcome to CSR!

From what you described.....that definitely sounds like an loose electrical connection. You definitely want to get to the bottom of that so that you don't find yourself stranded. I would start with the battery and ground connections.

What's odd is that it affects both engines simultaneously. Both engines have separate DC and computer systems but they do share a common ground. Has the boat had any work done in the engine room since last season that you know of?

 

[northern]

Have friend with 27 footer and he went across cruise ship wake 4 foot waves. All his electronics went out and next day they were back. Seems the sudden jar from the waves loosened something and it took a day for items to giggle back in place. He has not had the problem again. Has your boat been jarred recently. If so you may have a loose connection. It will be difficult to find. I would start with the fuse then with the connection. After that it is a matter of following wires and looking for loose things. I would do one item at a time wait a week and if no problem you found it. I once had a volt gauge read 8 volts I could not find the problem then one day I saw a loose wire in the 12 volt braker panel and that was the problem.

 

[bbwhitejr]

You should have the SmartCraft system and it should tell you the fault code(beep). Can also have a shop hook up a computer to the engines and tell you the fault.

Bennett

 

[LG111]

It's electrical. Start at the batteries and be sure all connections are tight. What volts are you at while running?

 

[techmitch]

Voltage drop!

 

[Michael Cooley]

Michael,

Welcome to CSR!

From what you described.....that definitely sounds like an loose electrical connection. You definitely want to get to the bottom of that so that you don't find yourself stranded. I would start with the battery and ground connections.

What's odd is that it affects both engines simultaneously. Both engines have separate DC and computer systems but they do share a common ground. Has the boat had any work done in the engine room since last season that you know of?

I just replaced all of the batteries and moved them to a new location. A lot of work in the engine room to include replacing of dripless shaft seal assembly

 

[scoflaw]

Did you increase cable size to accommodate for a longer run ?

 

[PlayDate]

I just replaced all of the batteries and moved them to a new location. A lot of work in the engine room to include replacing of dripless shaft seal assembly

That's interesting. How did you cable the batteries from the new location? Those connections are probably a good place to start looking for a loose or poor connection. My money is on a bad ground since both engines quit at the same time.

 

[rgerome23]

I posted the same issue in September. My mechanic has spend 20+hours trying to diagnose what is causing the issue. Mine has just been the port engine. It did it intermittently at the start of last summer and by the fall it was all the time. The engine never dies. It just kills all the electronics and re-starts the ignition. We tried to separate the boat from the engines to isolate. This way we would know if it was a mercruiser issue or sea ray. We thought it was mercruiser. There tech support was absolutely no HELP! We did everything he could think of in his 25+yrs of being a mercruiser mechanic. Swapped every sensor, computers, even the wiring harness. We still cant figure it out. I have all new batteries also. Then when he was winterizing the std engine did it! Now we are blown away and will have to dive back in to this mess in the spring. I have 2006 38 with 8.1 Horizon HO, Any help or suggestions would be appreciated. It used to just do it at initial start up. Now its all the time. Underway, at the dock and initial start up. It got progressively worse as the summer went on. It is not a ground issue. WE yanked and tugged on every wire and harness part and does nothing. We even replaced all spark plugs and wires. Please help!!!

 

[scoflaw]

Start your own thread with as much detail as possible.
What codes it throws etc.

 

[Sam Worsham]

I posted the same issue in September. My mechanic has spend 20+hours trying to diagnose what is causing the issue. Mine has just been the port engine. It did it intermittently at the start of last summer and by the fall it was all the time. The engine never dies. It just kills all the electronics and re-starts the ignition. We tried to separate the boat from the engines to isolate. This way we would know if it was a mercruiser issue or sea ray. We thought it was mercruiser. There tech support was absolutely no HELP! We did everything he could think of in his 25+yrs of being a mercruiser mechanic. Swapped every sensor, computers, even the wiring harness. We still cant figure it out. I have all new batteries also. Then when he was winterizing the std engine did it! Now we are blown away and will have to dive back in to this mess in the spring. I have 2006 38 with 8.1 Horizon HO, Any help or suggestions would be appreciated. It used to just do it at initial start up. Now its all the time. Underway, at the dock and initial start up. It got progressively worse as the summer went on. It is not a ground issue. WE yanked and tugged on every wire and harness part and does nothing. We even replaced all spark plugs and wires. Please help!!!

I have the same issue, but mine only does it at startup. When the engines are cold, there will be a single beep and the gauges all drop. This usually kills the motor and I have to restart it. Once warm, if I restart it, it will beep once and the gauges will drop, but the motor keeps running.
I thought it may be a water flow issue, like the computer doesn't immediately sense the water flow and gives a warning beep? When I first crank the motor, it takes a few seconds to see water flow from the exhaust ports on the side of the boat. On smartcraft, there are never any warnings or codes displayed.
I too have checked the ground wires and battery cables. At this time, it only happens at startup, so I wonder if its a low fluid, low battery, or what?

 

[rgerome23]

Mine originally only did it at start up. As last summer progressed it did it while under way also. I am perplexed and wish someone would tell us what to do to fix it.