2021 Yamaha F115 LB Motor Issue - Follow Up

[DiamondDave952]

I originally posted my motor issue a few days back and thought the issue was resolved. It turns out, it wasn't the battery cable connections as original thought by the dealership service tech. I want to get feedback/input from the community on my motor issue as I am disappointed to be having engine issues with only 40 hours. Let me explain what the engine is doing and the sequence of events.

2023 boating season, the engine performed flawlessly. I winterized the engine as usual ,but last year, I fogged the motor using Yamalube fogging oil and non-oxy gas mixture in a separate gas can. I removed the fuel line going into the fuel filter and connected a separate line to it to fog the engine and put the motor to sleep for the winter.

I dropped the pontoon in the lake back in late June to start the 2024 boating season. The motor started fine on the trailer (motor sounded normal), water was coming out of the tell-tail and started to back the pontoon off the trailer. I was going slow for a few minutes to allow the motor to warm-up. Battery voltage per the gauge on the dash was around 14V. I proceed to move the throttle forward to get the pontoon on plane and that's when the engine quit. Checked the primer bulb and it was stiff. Tried to restart the engine; the engine would crank but not start. Switch to battery 2 and tried to restart the engine, but it would not start. Got towed back to the dock and brought the pontoon into the dealership service center. The service tech thought it was a battery issue; cleaned the cable connections and ran the motor for 30 minutes either in a tank or using muffs without issue. Feeling relieved that it wasn't an engine issue, I picked up the pontoon from the dealership service center.

The next day, I dropped the pontoon in the water and just like the first time, when I move the throttle forward to get the pontoon on plane, the engine would quit and I could never get it to restart again. Not sure what to make of it. The only thing that I know is that when I move the throttle forward to put the pontoon on plane, that when the engine would quit (like the engine is starved for fuel under load).

Things that have been checked:

1. Batteries were load tested and found to be good.
2. Replaced fuel filter.
3. Replaced fuel/water separator. Tech did not find any evidence of water in the filter.
4. Fuel lines were inspected by the tech. Didn't find any issues.

Would love to hear from the community if they have encountered an issue like this before or what else to check. Hopefully, I can still salvage what's left of the boating season. Thanks!

 

[The Wanderer2]

You said you fogged the motor for storage. Are the plugs fouled out and in need of replacement?

 

[DiamondDave952]

You said you fogged the motor for storage. Are the plugs fouled out and in need of replacement?

I believe the plugs are good since the motor would start. It's when I try to get up on plane that the motor quits.

 

[The Wanderer2]

I had a jet boat that did that after fogging the engine for winter storage and it turned out the plugs were bad. Changed the plugs and the boat run normal again. Just a thought.

 

[DVW]

Plugs that are somewhat fouled will start with a rich mixture. Shortly after startup electronic control will lean out the mixture causing the engine to stumble and die with sudden load. If the plugs are somewhat fouled it could explain the stated symptoms.