115 MERC fourstroke intermittent issues SOLVED
Just following up on a previous post of mine trying to get to the bottom of this intermittent problem I had with my 2016 115 mercury.
This was my previous post http://fishwrecked.com/forum/115-merc-fourstroke-issues
So just a quick once over. I was experiencing a random period where the motor would run rough at lower revs and every now and then it did it at higher revs while driving in gear. After replacing every fuel line, completelty emptying and cleaning the tank, changing the tank pick ups, breathers, filters, spark plugs, loose electrical connections, pulling the control box apart etc I couldn't solve the problem. It didn't happen every time so you can imagine it was nearly impossible to take to a mechanic and say "fix it". The computer had never logged a fault or alarm so I was beginning to think I wasn't gonna get to the bottom of it.
After hours and hours searching through forums online I read an interesting post a bloke made experiencing a similar problem and his fix was a shift position sensor. I originally thought this is the "neutral position switch" that is in the control box that prevents you from starting the motor while you are in gear but its a different sensor. This sensor is actually in under the motor cover where the shift selection is. Tells the motors computer exactly when it's in forward reverse and neutral. Not sure if anyone else has done this but if you rev your motor up in neutral it limits the revs to about 2500 revs (or around about) and the motor shakes around like crazy and it doesn't sound nice. Obviously the computer doesnt want you to be able to rev the shit out of your motor while in neutral.
So what was happening was this switch was playing up. As I'm driving along at say 3000 rpm the switch for a spilt second tells the motor I'm in neutral and the computer limits the revs causing the motor to run rough. This malfunction with the switch was so fast it doesn't log a fault and you can't see it when plugged into the computer but would tell the motor to limit the revs.
My mechanic got on the phone to some other Merc mechanics over east and apparently there's been a few other cases like this around Australia. Merc said they will cover it under warranty since we've tried pretty much everything else. Changed the switch for a new one and I've been out about 7 times since and she hasn't missed a beat.
Hope this helps anyone experiencing similar problems. The problem was eating away at me for a good 6 months. Pays to keep digging there's plenty of people on the internet with problems you can learn from. Another fix i read with some of these strange problems is a faulty crank shaft position sensor. Can also cause issues. Before you go pulling apart your fuel pump or replacing the computer try replace these sensors (relatively cheap) when fault finding may end up saving you some money.
Cheers.
.
wifecallsmegrumpy
Posts: 148
Date Joined: 09/01/12
That's very interesting, I
That's very interesting, I have a Merc four stroke that had an intermittent pause at high rpm, but no codes thrown. The mercury dealer couldn't replicate it and ended up replacing the throttle position sensor as you did. Hasn't happened since.
dmck
Posts: 443
Date Joined: 07/03/19
Congratulations..
on your perserverance. Problems like that are diabolical to resolve.
You have done well and can be proud of your effort.
meglodon
Posts: 5981
Date Joined: 17/06/10
Well done
Persistence pays off
marrisy
Posts: 202
Date Joined: 08/09/11
Similar issues with my 115
Similar issues with my 115 suzuki. Replaced the shift position sensor at the front of the motor and problem hasn't reoccured.
Adam Gallash
Posts: 15648
Date Joined: 29/11/05
Interesting read
Interesting read. Cheers for the post Mitch.
Site Admin - Just ask if you need assistance
SeperateKnob
Posts: 668
Date Joined: 28/11/16
Awesome news. Thanks for
Awesome news. Thanks for sharing
scuttlebutt
Posts: 451
Date Joined: 24/03/06
Same sensor in my 2007 merc
Same sensor in my 2007 merc optimax 200 shit itself with only 50hrs on it. Went into safe mode and ruined a trip. I got the mechanic to remove it completely. I don't need a sensor to stop me from over-revving my motor in neutral...
little johnny
Posts: 5360
Date Joined: 04/12/11
So you can
Get them removed. My Andy had same issue with his optimax. Caused heaps of pain for a low priced part .
scuttlebutt
Posts: 451
Date Joined: 24/03/06
Yeah dunno if you have to
Yeah dunno if you have to use a jumper wire across the terminals but mine's been running fine without it for 8 years now.
moose hunter
Posts: 64
Date Joined: 14/06/13
A very good report Mitch
A very good report Mitch Westy
i have a 2019 115 merc and had very similar issues, I explained to dealer what was happening, took to dealership plugged computer in, no faults found, "must be fuel" no not fuel I said have checked fuel system from pick up in tank to all tank breathers, this went on for quite a while where engine would run rough cruising along, I would shut engine off, restart and all good, still no fault on merc vessel view. Next time fault happened I let it go for a while then finally code log appeared
back to dealer and yes faulty shift switch, interesting thing is that once fault logged in dealer computer showed up as about eight occurrences
anyway all good now,finally
engine now is incredibly smooth,quite and confidence restored in mercury
thanks for putting up your report westy
carnarvonite
Posts: 8672
Date Joined: 24/07/07
Etec
Had my etec motor stop and had to be towed in, after much trial and error found it to be the same sort of fault, the neutral switch in the throttle box had died.
Took old switch down to Jaycar and bought exactly same switch for a fraction of recommended genuine one. Replaced and works perfectly now.
dmck
Posts: 443
Date Joined: 07/03/19
Fortunate for you that you have the knowledge to use Jaycar etc.
So many boaties just dont... and the dealers have a field day.
Rob H
Posts: 5806
Date Joined: 18/01/12
Good report mate, this sort
Good report mate, this sort of thing helps people far past what the dealer guys even know as they dont share knowledge in this way.
Give a man a mask, and he'll show you his true face...
The older you get the more you realize that no one has a f++king clue what they're doing.
Everyone's just winging it.
NORUN NOFUN
Posts: 1035
Date Joined: 15/08/11
Great work, nothing better
Great work, nothing better than solving a real problem that no doubt would have driven you insane to work out.
moose hunter
Posts: 64
Date Joined: 14/06/13
Fortunately covered under
Fortunately covered under warranty where it gets a bit tricky for dealer as is intermittent fault and if no fault logged on computer and switch tested ok at dealership who pays for time? A - owner
can be very frustrating but dealer did compensate
being an old outboard mechanic I can see both sides of the fence
happy boating