Yanmar engine strange problem

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JeronimoMan

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My twin Yanmar engine 32ft motorboat suffers from a strange problem. If I hit some wake or slam even slightly to some wash (usually at 18kts), the starboard engine goes out of gear and revs up to max rmp (the clutch disengages but the engine does not seem to know about it) and the alarm goes off with a "Check Engine" message. Both propellers stop turning but the port engine does not rev up, just goes down to its idle RPMs. Throttles remain at cruising speed setting and need to get them back to neutral and then resume. When that happens, all dials momentarily go crazy (oil pressure, batteries etc).
I had Yanmar engineers and an electrician inspecting it for a long time. Everything at first glance seems tightly secured and all this related to some slight slamming causing something to move and propagate to all this. The diagnostic equipment shows the stb engine going to "safe mode" but it is unknown as to why.
We switched over the clutch electromagnets but exactly the same thing happened.
During all checks, both engine batteries were replaced, the electrical circuit was checked, one engine plug was found to have a pin slightly loose and got replaced, two nmea instruments were found to not be working properly and got unplugged to take them out of the equation.
Alas, the problem is still there.
The suspicions now are over to something electrical or maybe to the NMEA network.
Has anybody had anything similar?
 
JeronimoMan said:
My twin Yanmar engine 32ft motorboat suffers from a strange problem. If I hit some wake or slam even slightly to some wash (usually at 18kts), the starboard engine goes out of gear and revs up to max rmp (the clutch disengages but the engine does not seem to know about it) and the alarm goes off with a "Check Engine" message. Both propellers stop turning but the port engine does not rev up, just goes down to its idle RPMs. Throttles remain at cruising speed setting and need to get them back to neutral and then resume. When that happens, all dials momentarily go crazy (oil pressure, batteries etc).
I had Yanmar engineers and an electrician inspecting it for a long time. Everything at first glance seems tightly secured and all this related to some slight slamming causing something to move and propagate to all this. The diagnostic equipment shows the stb engine going to "safe mode" but it is unknown as to why.
We switched over the clutch electromagnets but exactly the same thing happened.
During all checks, both engine batteries were replaced, the electrical circuit was checked, one engine plug was found to have a pin slightly loose and got replaced, two nmea instruments were found to not be working properly and got unplugged to take them out of the equation.
Alas, the problem is still there.
The suspicions now are over to something electrical or maybe to the NMEA network.
Has anybody had anything similar?
Click to expand...

Tel us more , what engine model and drive model , and boat builder.
 
I guess you have electronic controls, have you checked inside the boxes or controls for damp?
I got some water into the box containing all the electronics, gave very weird behavior at certain times, depending on temperature, movement etc.
Imagine my surprise when trying to anchor in the dark and neutral became forward and reverse neutral, took several minutes of me swinging around the anchor to figure out what was going on.
 
They are electronic controls indeed. I will check them, cheers.
However that behaviour occurs with either helm controls in operation, but good point anyway, it could be coming from any defective gauge if any.
Just very hard to replicate that particular problem at anchor or otherwise.
Your problem must have been very puzzling, to say the least.
 
What a frustrating problem. Given that BOTH engines go out of gear, albeit displaying different symptoms,my money would also be on the control box.
 
Both control boxes seem ok but after inspecting all wires, I discovered that when shaking some, an engine fault came up, probably from some loose connection or short. I tidied everything up and now and secured them. It now remains to be seen what will happen during a sea trial.
 
Good luck. I don’t know enough about the control boxes or how they work to be helpful, but just because all the connections are good doesn’t mean they will do what they are meant to ! You could see if you can replicate the effect of going over a wave by removing the control box from whatever surface it is mounted on and replicating the shock (I.e. hitting it ! ). If that is the issue..... just replace them, expensive as they will surely be...... otherwise they will drive you crazy !!
 
I have recently been trying to go over my own waves to replicate the problem. I have been hitting, kicking etc everything in order to try to create that situation. I will surely do try to hit and shake everything (the upper control box is mounted on polyester and the lower one on a metal top - they don't actually move too much themselves) as for the waves, they are hardly a shock to the boat, so my guess is focused on some loose wiring/connections, at least to the ones that are accessible. As the problem does manifest itself from either helm station, I am not convinced that both controls suddenly went faulty (assuming that when one of the is inactive, it does not short circuit the bus network). Of course all days now here are totally calm so no sense to go out and try to replicate the problem just yet. I will do it asap thought and get back with more info.
 
Seems the problem is now fixed. After obsessively securing all loose wiring everywhere with cable ties and insulating some naked cables, going now over steep waves and trying to "slam" the boat, does not activate so far any engine alarms of any sort (and therefore clutch disengagements). Seemed to be the easiest and most obvious solution which was rejected from all Yanmar engineers/electricians and others when I had pointed this out to them a long time ago and they were directing me to solutions such as parts replacements or whole (!) engine wiring replacements or..both. It's worth mentioning that all loose wiring was the result of some authorised marine instruments' installers, when I added some extra things to the boat. The manufacturer (Sessa) had everything neat, tidy and secure in a proper marine fashion.
 
that's a good result. in the unlikely event the problem should return at least you know its wiring related and just have to patiently work through it all. Fingers crossed job done.
 
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