Yamaha F115TXRB Surging

[fishnfvr]

I am new to this site and wasn't sure where to turn before I head to the service shop.
Here is some back ground, 4 years ago had injectors cleaned serviced, VST cleaned, every year filters and fluids changed. Replaced fuel lines , tank vent line, I am sure there are other things just cant recall at the moment. engine has less than 300 hours on it.

This weekend, had the boat out, started up great. Idled thru the no wake zone, got up on plane and ran great. Upon getting close the fishing grounds and coming off of plane, boat felt like it was surging??? Went back to Top End, boat ran great no surging. I noticed my low and mid-range seems to be an issue with surging. wanting to stay out a little longer I went to start and it sounded like it was struggling but it started. Headed back to dock ( again top end no issue ) coming off throttle.. surged really bad at low rpms.
took boat home, inspected oil level - ok, coloration - ok, removed spark plugs, all same color no evidence of any issues, poured gas from fuel water separator in glass bowl - clear. I noticed a blue and yellow wire near the throttle arm that ran to the fuse cover in front of the engine. I removed the cover and a grey with black jumper wire was sitting on the bottom of the cover.
My question is, should this be plugged in? I can see where it goes ( diagnostic connector ) because it is the only receptacle without anything. I cant imagine Yamaha would place this in the cover and have it bounce around if it wasn't to be used. I am not sure if this will fix my surging but it is a start.
Any help / ideas will be greatly appreciated.

[fairdeal]

not sure I'm following - this "blue and yellow wire" is "loose" ?

not connected to anything?

AFAIK the only blue/yellow is for the shift position switch.

I'm fuzzy on what surging means -

but it is interesting to imagine the possible effect of a loose shift position switch wire...

I suppose , if it happened to come in contact with "ground". the ECU would react as if the engine were in neutral - and impose an rpm limit...

[fishnfvr]

I was just looking at all my connectors and followed a blue wire with a yellow stripe to the fuse box. After removing fuse box cover, a grey plug with a black jumper wire fell out and am not sure if it should be plugged in. For some reason when I try to load pic, it says system error so I am unable to post pic. On this engine this engine, there are two green fuses, then two yellow, then a female connector that is held on by a single screw. This is where it fits. I m just afraid to plug it in, if it's not supposed to be.


My issue is, my engine is surging ( rpms jump up and down ) at low and mid range ( 1000 Rpms - 4000 rpms ). From 4000 on, no issues at all.

[fairdeal]

the gray plug with black jumper is the diagnostic connector - it doesn't get "plugged in" anywhee

actually, its the connector, safely covered with a protective cap -
its the cap that has the jumper wire - the cap is removed when connecting the laptop.

[fishnfvr]

I still have to learn how to post a pic for future reference and clarity.

That is the connector, the one with the string on it. That was just lying inside the fuse cover which I thought was weird and was hoping this may be my issue. Unfortunately not.


I appreciate your reply and posting the pic.

Now I have to figure out why / what is causing the rough running when not on plane. I will be making a call to the boatyard to tomorrow to see when they can fit me in. I am sure it will be a few weeks but I will post the answer once resolved.

Thanks again

[fishnfvr]

Slight update

A representative from Yahama called me and said, it should be plugged in. This will not fix my issue though. He said it sounds like it could be a Throttle Position Sensor or IAC and recommended bringing it in to a shop where they can check with the laptop.

Hopefully next week I can get it in, meanwhile, I will be ordering a service manual which may instruct me on how to check / set the TPS sensor.

we'll see...

[fairdeal]

thinking about your single "blue & yellow wire" - wondering if it could be the Diagnostic Flash Indicator lead -
which is blue/white - but perhaps yellowed

is this it?



if so, that does not get plugged into anything,
except a special Yamaha test light for diagnostic purposes

[fishnfvr]

They grey plug you have picture was the item that was laying, rattling in my fuse cover and fell out when I removed it. Yamaha told me last night, it should be plugged in but it only protects the terminals for the diagnostic port.

Upon closer inspection last night, the "blue" wire that I followed, was actually a blue cover that covered two wires from the throttle position sensor. I am tempted to order one but if it needs to be set, I don't have a service manual yet to instruct me on how to adjust it. I am going to try ordering a service manual tonight.

I am still wondering if it could be a stuck thermostat. I am going to take it out tonight to inspect it until the one I ordered arrives.
it's just weird above 4000 rpms, she runs great. she started and purred last night on land as if - no issues . it has been 2 years since I replaced it

I gotta thank you for your replies, that means a lot to me.

I will keep this updated just in case anyone has a similar issue. hopefully I will figure out how to include pics. it told me, error contact site administrator.

Good luck to you and be safe out there
Joe

[fishnfvr]

Slight Update-

Received a call from the mechanic today. I had a couple codes:
1 was: engine was shut while still in gear ( I know I did that when I had someone almost run into the back of my boat while my help was winching me in. I shut it off and pushed their boat away.)
The other was- something about overcooling which he said it is normally from a thermostat stuck open.
Spark plugs - all look good, all burning the same. they hooked something up to check coil packs or something and no issues.
They mentioned my throttle position sensor was a little off. it was reading negatives instead of positives or something like that. I was just getting ready to hear the $$$$ signs and was nervous. They re-set it and said everything looks good.

They also said, if the issue is still there when I put the boat in the water to drive it to them and they can do other tests in the water.

Once I splash the boat ( hopefully this weekend ) I will confirm and post.

[fishnfvr]

further update:

took the boat out for a test ride. first 30 minutes, she ran like a champ. I was very excited and called my dad to give him the 411. within minutes of talking to him on the phone, the engine started acting up again. Praying it was my imagination, I brought the engine down to no wake speed and it did it two more time . I called in on the radio to the shop and brought it in by water. Boat was doing it the entire time.
tied the boat to the dock and talked to the mechanic and told him the issue is still there.
they take the boat out a little later that day ( twice they said ) and called me. they told me this is one of the best running F115's they have seen. as happy as I was with that, it still doesn't fix my issue. they said, we're going back to the boat to check a few things out and we'll call you back.

hour goes by and they said, the first time I brought the boat in, there were codes. 1 for over cooling, 1 for pulsating coil, and something about shutting the boat off while in gear. they previously cleared all codes. they went back and the same pulsating coil code was back.

i'm thinking- hey it must be it, change it. they said, I want you to take the boat out again and when / if it happens, bring it by water and they will get right on it and see. they said they want to make sure it is the pulsating coil and not something else bringing on this code.

as happy as I am that they are not just parts changers, it is starting to get a little frustrating. it has to be tough bringing in a boat, claiming there is an issue, then the mechanic jumps on and they don't see / feel it.

I will keep this updated just in case anyone has a similar issue