2003 Yamaha VZ225 Dies While Idling

[dwparker99]

I've got about 22 hours on this motor since the power section was rebuilt by a marine repair shop. The injectors were serviced and the filters were changed/cleaned. Shortly after the rebuild, the engine started dying while idling, mostly when shifting to neutral but sometimes when just idling. When it dies, it is really hard to get started. I have to keep the starter engaged while it is hitting but isn't making enough power to run. It always runs fine on top end. Before chasing a fuel issue, I'd like to confirm it is not the neutral or shift cut switch. The way I understand these switches work is this: When in neutral, the neutral cut switch causes the engine to run on 4 cylinders. When shifting to forward/reverse, the neutral switch is disengaged and lights up the other two cylinders and the shift cut switch is (disengaged/engaged?) which briefly lowers RPMs to make it easier on the lower unit gears.

After initial post, I checked to see how the shift cut switch is operating. The switch closes only when going to neutral from forward/reverse. On the shift handle, when I go to reverse detent or full reverse, the switch closes when going to neutral. When going to forward detent and back to neutral the switch never closes. When going to full forward, the switch closes when going to neutral. Is something out of adjustment and would this cause it to die when idling?

Questions

Is this how the two switches work?

If so, could the shift cut switch be intermittently giving the signal to the ECU to lower RPM when in neutral causing the engine to die?

If so, how does the ECU lower RPM via the injectors or ignition?

I would like to get the diagnostic software to monitor engine output on my computer. Is the YDS 1.33 package you see on Ebay form China legit?

I appreciate any and all responses.

[forrestercb]

I have the same motor and mine is doing the same thing after having it rebuilt a couple months ago.

[Thamelau]

The neutral switch is just how you have explained, when in neutral, the switch is made, and it cuts 2 cylinders.

I believe the shift cut switch is never meant to be made, unless shifting while underway in the water. The water causes the system to have a tougher time shifting while the power train is loaded. This causes the spring loaded mechanism to load up, make the switch, and cut 2 additional cylinders. It acts independently from the neutral shift, and affects different cylinders I am pretty sure. When I was having really bad motor issues, both sensors were not correct and I believe my motor was attempting to run on 2 cylinders, unsuccessfully though.

My China YDS 1.33 is a life saver. It saved me a lot of shop time being able to see the sensors, and mine came with a PDF manual for my motor. It definitely is a tool, and not a cure though. You still have to draw conclusions from the outputs it is giving you.

[dwparker99]

Thanks for the reply Thamelau. In reading other threads, it seems the consensus is that the shift cut switch should be made anytime you shift into neutral. This causes the engine to misfire/hiccup/lose power which unloads the prop making it easier to pull the clutch dog away from the gears. Mine is not being made when I shift from forward to neutral. I originally thought this may be causing the ECU to go squirrely but the more I think about it the more I think that that is not the case. This evening I noticed that the bracket that holds the shift rod bushing is cracked up toward the front and I think this is keeping the bracket from pivoting like it should to engage the switch. This BOAT (Break Out Another Thousand) is getting old quick.

I did order the YDS 1.33 software so hopefully it will help me discover the problem with rough idle/dying.

[Thamelau]

I cracked my bracket while dropping the power head back in, that is what started all my issues hahaha.

[dwparker99]

I cracked my bracket while dropping the power head back in, that is what started all my issues hahaha.

How difficult was it to replace it and get it adjusted correctly?

[Thamelau]

Not bad, I just had the big wire loom to move and used a long out of pliers to unpin everything and carefully wiggled it out

[dwparker99]

Not bad, I just had the big wire loom to move and used a long out of pliers to unpin everything and carefully wiggled it out

I'm waiting for my bracket to arrive before I tear into it. It looks like there is a spring under it. Does the spring have to be preloaded somehow?

[Thamelau]

I'm waiting for my bracket to arrive before I tear into it. It looks like there is a spring under it. Does the spring have to be preloaded somehow?

no, it will be pretty self explanatory when you dig in there. I think maybe less than 1/4 turn of pre load

[dwparker99]

no, it will be pretty self explanatory when you dig in there. I think maybe less than 1/4 turn of pre load

I appreciate the help. One more question. Can the bushing be put in backwards? The reason I ask is mine is installed with the sharp edges toward the switch. In the parts drawing, it looks like the round edges are toward the switch.

[Thamelau]

I assume the bushing you are talking about is what I call the shifter linkage slider thing that engages the neutral switch. Mine is round towards the switch. I imagine it would function either way, but with the sharp edges toward the switch you risk bending the sheet metal switch actuator over

[dwparker99]

New fuel pumps fixed my idle problem. My idle problem got worse and the motor started to make a strange "dieseling" sound when coming off plane. I also noticed the primer bulb was taking longer to pump up. I read in one of the threads here that bad fuel pumps could cause strange things, so knowing mine were at least 8 years old, I ordered 2 new ones. When replacing the lower one, I backed it away from the motor and pump the bulb and fuel came out the back. Replaced both and now bulb gets firm after 2 pumps and motor runs and idles much better.

[tyfoford]

Good news on the pumps! I have the same engine, same problem. I have two pumps on order and your problem solving gives me hope that I have the same issue. Thanks for the report!