Runaway 2008 150 Optimax - fuel spilling on port side

[jones76845]

2008 150 Optimax SN: 1B555755


Boat ran fine going to first fishing spot, after 30 minutes of fishing was idling out of 5mph zone and out of nowhere the opti decided it was going to go to full throttle, tried throttling up and down but no change, attempted to get out of gear but could not, ended up having to shut down in gear. Put back in neutral and tried firing up again and it immediately tried to rev to full throttle, shut her down fast. decided I better check things out under the hood, removed the cowling only to find gas streaming from the top of the motor on the port side, scared the you know what out of me, raced to get the fire extinguisher just in case. I have attached a photo showing where the fuel was streaming from, and were not talking little drops of fuel were talking a major stream. Long story short, after a hour and a half burn with the trolling motor to get back to the main body and flag down a boat for the dreaded tow of shame back to the launch ramp, I am waiting to get her into to a certified mechanic for repairs. Was wanting to get any info from the experts here on possible causes, always best to go prepared with info when taking her into the shop.

[clayshooter100]

Likely caused by a problem with the needle/seat assembly in the vst not shutting off the fuel flow when full. That black hose almost below your red arrow is the vent line from the vst, if you pull that line off and pump your bulb you will likely see fuel running out of that line. The motor is revving from some of that excess vented fuel making its way into the air intake.

[EuropeanAM]

Likely caused by a problem with the needle/seat assembly in the vst not shutting off the fuel flow when full. That black hose almost below your red arrow is the vent line from the vst, if you pull that line off and pump your bulb you will likely see fuel running out of that line. The motor is revving from some of that excess vented fuel making its way into the air intake.

+1

[Bass AHolic]

the gizmo mentioned in the warning start n gear device . in the control box ??

[jones76845]

Great thanks for the feedback, My appointment is tomorrow, will update you on the findings.

[R&M team]

2008 150 Optimax SN: 1B555755


Boat ran fine going to first fishing spot, after 30 minutes of fishing was idling out of 5mph zone and out of nowhere the opti decided it was going to go to full throttle, tried throttling up and down but no change, attempted to get out of gear but could not, ended up having to shut down in gear. Put back in neutral and tried firing up again and it immediately tried to rev to full throttle, shut her down fast. decided I better check things out under the hood, removed the cowling only to find gas streaming from the top of the motor on the port side, scared the you know what out of me, raced to get the fire extinguisher just in case. I have attached a photo showing where the fuel was streaming from, and were not talking little drops of fuel were talking a major stream. Long story short, after a hour and a half burn with the trolling motor to get back to the main body and flag down a boat for the dreaded tow of shame back to the launch ramp, I am waiting to get her into to a certified mechanic for repairs. Was wanting to get any info from the experts here on possible causes, always best to go prepared with info when taking her into the shop.

i have a 150 opt max and had a leak to from high fuel pressure line had to replace line almost 400.00 dollars

[jones76845]

Yeah I had the same thing happen to me in 2013, I was fortunate that I had 3 months left on my 5 year warranty and Mercury replaced for free. As my mechanic said when he found it during my annual routine maintenance, "Did you know you were driving around the lake with a 150 HP bomb strapped to the back of your boat". He also says that Mercury refers to it as a "THERMAL EVENT"

By the way, they replaced the needle valve and float, mechanic said they have changed the design so they must have known there were some issues.

New part# used: 8554301A1 Float Kit
883252 Gasket