2006 Mercury 115 EFI Stalling at Full-throttle
Posted: Sun Apr 24, 2022 7:22 pm
I have an intermittent but annoyingly recurrent problem with my 2006 Mercury 115-HP FOURSTROKE EFI motor that has escaped diagnosis and which no one can seem to fix.
This 2006 engine is from an apparently short lived-joint venture with Yamaha, and has less than 650 total hours.
Beginning about three years ago, the 2006 Mercury 115-HP FOURSTROKE EFI engine occasionally and quite suddenly would cut out when running at full throttle. Since then, and at least 50 times, the engine has suddenly lost power.
The sudden loss of power usually happens toward the end of the day angling, after five to six hours of making five to ten runs to new spots. The sudden loss of power has always occurred within the first 300 to 500-years of a run, and always at full throttle. And it is more likely to occur when the ambient air temperature is hot.
On some cool winter trips it does not occur for a week on the water.
When the 2006 Mercury 115-HP FOURSTROKE EFI engine stalls, I’ve found that if I immediately put it into neutral and go back and re-pump the primer bulb (which invariably is deflated and requires a lot of manual pumping to fully inflate), I can keep it running. At the time it also smells strongly of gasoline fumes.
After I get the primer bulb re-inflated, the 2006 Mercury 115-HP FOURSTROKE EFI engine generally runs well, but it can stall again on the next full throttle run when the air temperature is greater than about 75 degrees.
Only once did it actually stall out completely. At that time, I was unable to immediately restart it. I had it towed to a marina. There was no mechanic to be found and it started right up after about an hour and it ran fine.
Since the problem started, I have made sure to re-prime the primer bulb before every run. This strategy has successfully gotten me through the days on the water, but it has not been ideal.
One trip was reality hot, and the primer bulb kept getting soft, so I had to pump it up every 20 minutes, even between casts. The 2006 Mercury 115-HP FOURSTROKE EFI engine stalled twice even after re-inflating the primer-bulb immediately before the run, and sometimes it took 20 to 30 pumps to get the primer bulb firm. This prompted several conscientious attempts to get the problem fixed.
I've had the boat to the reputable mechanic that services the boat three times without resolution of the problem. Mechanics from two other shops took it on the water, but were unable to reproduce the stalling. I took it on the lake for several hours with an auxiliary gas tank but also was unable to stall the motor. Immediately after unhooking the auxiliary tank, it wouldn’t stall running it off the boat’s tank either.
Multiple new parts have been thrown at the problem.
The 2006 Mercury 115-HP FOURSTROKE EFI stalled out during my last trip in characteristic fashion. I called my current mechanic who came out for a ride and attached his diagnostic computer, but I was unable to stall the boat with him in attendance. He said that the starter and new rectifier seemed hot, and there might have been low air pressure. These were of unclear significance.
The problem is recurrent, but infrequent enough that it is difficult to reproduce on demand. When it occurs, I have to re-inflate the primer bulb to get the motor to run, and to take the boat to the shore to pick up the mechanic, and this make it unlikely to stall again in a time frame that the mechanic can afford to ride in the boat to diagnose the problem. So I have little hope of reproducing the problem under observation.
I use high quality regular gas with some ethanol, I've used Stabil with no apparent change.
Give me a suggestion [for the cause or the remedy]
I’m fairly sure [the problem is in] the engine and not in the fuel [system].
Q1: could this be some weird type of vapor lock?
Q2: is the motor overheating in some way?
Q3: is [the cause due to] some type of sensor failure?
Q4: why is the primer bulb always deflated when the motor stalls?
Q5: why is this getting more frequent?
Q6: why is [the occurrence of the problem] worse in hot weather?
Good mechanics and I [are both] at wit's end. I’ve spent about $3,500 on an engine that cost me $9,500 in 2007. Maybe it’s time to buy a new engine.
This 2006 engine is from an apparently short lived-joint venture with Yamaha, and has less than 650 total hours.
Beginning about three years ago, the 2006 Mercury 115-HP FOURSTROKE EFI engine occasionally and quite suddenly would cut out when running at full throttle. Since then, and at least 50 times, the engine has suddenly lost power.
The sudden loss of power usually happens toward the end of the day angling, after five to six hours of making five to ten runs to new spots. The sudden loss of power has always occurred within the first 300 to 500-years of a run, and always at full throttle. And it is more likely to occur when the ambient air temperature is hot.
On some cool winter trips it does not occur for a week on the water.
When the 2006 Mercury 115-HP FOURSTROKE EFI engine stalls, I’ve found that if I immediately put it into neutral and go back and re-pump the primer bulb (which invariably is deflated and requires a lot of manual pumping to fully inflate), I can keep it running. At the time it also smells strongly of gasoline fumes.
After I get the primer bulb re-inflated, the 2006 Mercury 115-HP FOURSTROKE EFI engine generally runs well, but it can stall again on the next full throttle run when the air temperature is greater than about 75 degrees.
Only once did it actually stall out completely. At that time, I was unable to immediately restart it. I had it towed to a marina. There was no mechanic to be found and it started right up after about an hour and it ran fine.
Since the problem started, I have made sure to re-prime the primer bulb before every run. This strategy has successfully gotten me through the days on the water, but it has not been ideal.
One trip was reality hot, and the primer bulb kept getting soft, so I had to pump it up every 20 minutes, even between casts. The 2006 Mercury 115-HP FOURSTROKE EFI engine stalled twice even after re-inflating the primer-bulb immediately before the run, and sometimes it took 20 to 30 pumps to get the primer bulb firm. This prompted several conscientious attempts to get the problem fixed.
I've had the boat to the reputable mechanic that services the boat three times without resolution of the problem. Mechanics from two other shops took it on the water, but were unable to reproduce the stalling. I took it on the lake for several hours with an auxiliary gas tank but also was unable to stall the motor. Immediately after unhooking the auxiliary tank, it wouldn’t stall running it off the boat’s tank either.
Multiple new parts have been thrown at the problem.
- I’m on my fourth new primer bulb
- a new low-pressure fuel pump assembly
- a new anti-siphon valve
- a fuel pick up
- a kinked part of the fuel line removed
- a redundant part of the fuel line were removed
- the entire fuel line from the tank to the motor replaced
- all the fuel filters were replaced
- removed an in-line water separator
- the deck was taken up three times so that the fuel pickup, the anti-siphon valve and the tank could be re-inspected and they were found to be okay
- recently the Vapor Separator Tank was removed and inspected; a new needle, seat, high pressure pump and pressure regulator were installed
- the rectifier failed and was replaced-- but I think that this was probably unrelated.
The 2006 Mercury 115-HP FOURSTROKE EFI stalled out during my last trip in characteristic fashion. I called my current mechanic who came out for a ride and attached his diagnostic computer, but I was unable to stall the boat with him in attendance. He said that the starter and new rectifier seemed hot, and there might have been low air pressure. These were of unclear significance.
The problem is recurrent, but infrequent enough that it is difficult to reproduce on demand. When it occurs, I have to re-inflate the primer bulb to get the motor to run, and to take the boat to the shore to pick up the mechanic, and this make it unlikely to stall again in a time frame that the mechanic can afford to ride in the boat to diagnose the problem. So I have little hope of reproducing the problem under observation.
I use high quality regular gas with some ethanol, I've used Stabil with no apparent change.
Give me a suggestion [for the cause or the remedy]
I’m fairly sure [the problem is in] the engine and not in the fuel [system].
Q1: could this be some weird type of vapor lock?
Q2: is the motor overheating in some way?
Q3: is [the cause due to] some type of sensor failure?
Q4: why is the primer bulb always deflated when the motor stalls?
Q5: why is this getting more frequent?
Q6: why is [the occurrence of the problem] worse in hot weather?
Good mechanics and I [are both] at wit's end. I’ve spent about $3,500 on an engine that cost me $9,500 in 2007. Maybe it’s time to buy a new engine.