Yamaha V4 115 extreme miss above 2,000 rpm's, fixed by touching trim button

bluespeedball

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Sep 11, 2011
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5
Guys I apologize in advance for the stupid questions that I will be asking on the forum but I appreciate and and all help I can get. I purchased my first boat a month ago, a 1992 Alumaweld H56 with a Yamaha V4 115 Model C115TLRP. I purchased it from a widow whose husband bought it new in 2000. He passed away and it went to her son who also passed away. It has sat in a garage for the past 5 years and probably used less than 10 times. And for those of you that are thinking it No the boat isnt cursed......i think.

I brought it home and immediately drained the old gas out of the gas tank and filled with new 93 octane with the correct 50.1 ratio of Yamaha brand oil. I had a friend help me change the lower gear oil, installed new plugs and I paid someone to change the water pump as a preventive measure. I have to buy all 3 new batteries ( 1 start and 2 deep cycle for the 24v trolling motor. The boat it hardwired from the factory with circuit breakers instead of fuses. It has power tilt and trim and it does appear that someone has replaced the key switch at some point. That the history of the boat.

I have a healthy knowledge of automobile engines but very limited on my experience with boat motors. Heres my issue; the boat will not run above 2,000 rpm's with a severe stalling/ missing/ hesitation whatever your want to call it. It feels like at 2000 I have 1-2 coils that shut down. On my first test run I was just at idle making sure the boat didnt leak, that bilge pump and live well pump worked and things like that. I attempted to engage the throttle about 3/4 and it began to miss like I had lost a coil or two. I dont know what a two stroke suppose to sound like at idle, but this one sounds decent. While it was sputtering I began to play with the tilt and trim button and when I hit it, MAN it lit up and ran like it was being chased by the devil! Due to the sputtering I went back to idle and put it on the trailer.

I have read everywhere that these carbs will get junked up from sitting so I purchased two cans of spray seafoam and two can of mix. I mixed one can in a gallon of gas w/ oil and ran it at above idle through the engine. I poured the other can in the gas tank. I took apart the carbs and sprayed/ cleaned them but they were spotless on the inside. I decarb the boat with the other can as I have found instructed online. At this time I had a new trolling motor installed so i wasn't as afraid to get out in the water with it. I also tested all 4 coils to make sure ohms were within specs (yes I bought a v4 115hp manual). The coils were all within spec.

Today I took it out for the second time after the carb cleaning, decarb and coil test. Put it in the water and used choke, it started almost immediately. I put it in idle and eased out into the main channel. At this time I let the boat warm up for about 5 minutes. After this I started to engage the throttle a little more. Again at exactly 2,000 rpms the boat starts to sputter/ miss/ hesitate whatever you want to call it. I did fish this evening and on the way back decided to fully engage the throttle to see what would happen. I did and it started the missing immediately after 2,000 and wouldn't climb any higher. I remembered the trim/ tilt button and pressed it and she TOOK OFF! Im not talking about pressing and holding the button, but steady pressing the button every 1/2 second either up or down this boat is trying to come out of the water. After you release it she sputters and falls down below 2,000 rpms.

This boat is almost all stock, except for the key switch, trolling motor, batteries and fish finder. Im racking my brain here. If the coils were going out or bad, if the carb was dirty or gunked up the why is it running so well when I pressing the trim button. AND......why is the intermediate pressing off the button making the boat run like it should. This appears to me like a short in the wiring BUT what about the trim button and a short would IMPROVE performance? Shoudnt it decrease the performance? What should I look for in regards to the short, should I follow the trim power wires, inside the control box or something about the motor in the back? Should I ever be concerned about the coils or carb at this point.

I feel helpless that I have no further knowledge on this subject, I can do the work if Im just pointed in a direction to go in. I have spoken to two local boat mechanics that state the boat is probably just old. I have a lot of trust issues with shadetree mechanics, and the larger companies want to sell you another boat. I know this was a long post but if anyone could provide so help it would be so greatly appreciated.

i will respond quickly if anyone has any further questions or if I need to try something before we go any further.

Thanks
Robert
 

99yam40

Fleet Admiral
Joined
Sep 7, 2008
Messages
8,851
Re: Yamaha V4 115 extreme miss above 2,000 rpm's, fixed by touching trim button

my thoughts are a bad ground or some shorted wiring

You need to be testing to see if it is electrical, loosing spark

A quick check of all plug wires with an inductive timing light should show if you are dropping spark to some plugs

Test the inputs and out puts of the CDI both before and while problem is occurring to see if voltages are good to that point
 

bluespeedball

Recruit
Joined
Sep 11, 2011
Messages
5
Re: Yamaha V4 115 extreme miss above 2,000 rpm's, fixed by touching trim button

Guys thanks for all the help so far. This is what I got at the present time.
Took the boat out to the water after changing the poppet valve, t-stats and hooking up the alarm where it was previously unhooked. Left it on the trailer but backed into the water and again it would start but not rev over 2000 rpms. The alarm sounds as soon as you turn the key on and will not stop. Its not hot, its not even started and the alarm buzzer is sounding. BUTTTTTTT.......with the key on, the alarm going off, when I hit the tilt trim button up the alarm stops for as long as I hold the up trim button.

Now dealing with the alarm, I have disconnected both temp sensors and the alarm continues, I mix my own oil so thats not an issue. The alarm will stop by unplugging either wire (yellow or pink) that goes to it, disconnecting main harness from motor (therefore killing the power) or dis connecting the red fused wire going to the starter relay. Problem is all of these things kill the power going to the alarm but nothing I do seems to effect the closed grounded circuit causing it to go off.

Now as far as the trim button, I can disconnect all 3 wires going to the trim button, turn the key on and the alarm still goes off.

WHAT IS GROUNDING OUT?!!!
 

divinginn

Petty Officer 3rd Class
Joined
Aug 12, 2007
Messages
77
Re: Yamaha V4 115 extreme miss above 2,000 rpm's, fixed by touching trim button

Does it still have the oil injection system installed? With the alarm system going off the motor is going into limp mode to keep from damaging the motor,you need to find out what is causing the alarm to go off. The alarm will go off when the oil resivor is low or when the engine is getting too hot.
 

Bamaman1

Lieutenant Commander
Joined
May 15, 2011
Messages
1,895
Re: Yamaha V4 115 extreme miss above 2,000 rpm's, fixed by touching trim button

I also have the same engine, however mine is a 1985 model with the model 703 Yamaha controls and a Yamaha analog tachometer with the lights that indicate engine problems. The Yamaha 115 hp 2 stroke has a reputation for being bulletproof.

The only time I've ever experienced the 2000 rpm fault is when I let the oil level get too low. There are floats in both the external oil tank and the small oil tank (inside the cowling) that measure when the oil level is low--and will cause the alarm and limp mode to go off.

There is an electronic oil module below the small oil tank that can cause problems like not stopping the oil pump on the big tank to quit when the little tank is full. The oil injection system on this motor is mechanical and it's pretty trouble free.

I have an aftermarket service manual, and suggest you also get one to fully understand your motor.
 

99yam40

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Joined
Sep 7, 2008
Messages
8,851
Re: Yamaha V4 115 extreme miss above 2,000 rpm's, fixed by touching trim button

chase the pink wire it is the one that gets grounded and sounds the buzzer.
Not sure if the it goes to the CDI and the CDI grounds it when it gets the signal from the temp switch or if the switch is the only thing that controls the ground, but my bet is on the CDI. See if you can disconnect it from the CDI to see if that will stop the buzzer
The yellow is key on power, and the buzzer has power to it when as long as you have the key turned on.

a short in the wiring is still my thoughts.
See if there is a connection(Continuity) between the tilt wiring and the pink ( my bet is on this one)

and if not then see if you loose 12+ on the yellow to the buzzer when pushing the trim.( not very likely)
 

bluespeedball

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Joined
Sep 11, 2011
Messages
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Re: Yamaha V4 115 extreme miss above 2,000 rpm's, fixed by touching trim button

99yam40, you are correct! After I fixed the buzzer and took it out in the water the buzzer would go off even without the engine running. The "miss" but actually the limp mode was still there.

I began pulling wires and found the the trim up switch (blue wire), would turn the alarm off when I unplugged it. I then checked the engine side of the wiring harness and found no continuity between the pink and blue wire. I then checked the control side of the main 10 pin harness and had continuity between the pink and blue. I cut the harness halfway and checked the wires again and traced it to the actual plastic harness plug (the one with the female pins had a short at the plug. You could push and pull and the short would go away, then appear back at a later time. I bypassed the blue wire by running one directly and it fixed the limp mode issue but now have no tach and appears to be no engine timing advance. I have a new harness on order.

Thanks
everyone for your help!
 

99yam40

Fleet Admiral
Joined
Sep 7, 2008
Messages
8,851
Re: Yamaha V4 115 extreme miss above 2,000 rpm's, fixed by touching trim button

Not completely sure about your motor, but on my C40 that( timing not advancing, nothing to do with the tach) is what happens if the CDI gets the signal that motor is too hot from temp switch.
This is how the limp mode limits the RPM to 2000( retards timing).
Did the tach work ok before you cut the harness?
you may have some other problems as well, but need to fix what you can and then keep looking

How did you disconnect the blue wire from the harness?
If the wire is still hooked up on one end it could still be sending a ground to the CDI.
Did you trace the pink wire to where it ended up on the motor?CDI or temp switch, or both?
 
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