Mercury 75hp made in 1986. s/n A932083
This is now a pattern, starting about 3 months ago: Starts easily and idles perfect at the launch ramp. Leave it running while I put my truck away, it's been idling 8-10 minutes by the time I'm ready. Another 4-5 minutes at no-wake speed. Power up to 50% or so, then after a few minutes of that...BAM! It starts to sputter and miss and lurch, then the RPMs quickly and steadily drop to idle level, even though I haven't touched the throttle. It doesn't shut off, it just powers down. Bringing the throttle back to neutral has no effect, pushing the throttle forward does nothing. It just coughs and sounds rough as hell for about 30 seconds. I turn off the ignition, restart it....maybe do that a couple of times. Same thing: throttle forward, nothing...sputters and misses.
Then, as if it just decided that's enough...it jumps out of the hole and away we go like nothing happened. For the rest of the day, whether it's an hour or six hours, zero issues. Smooth running, immediate starting, good hole shot, perfect.
It only does that weird thing ONCE, for 30 seconds or a minute, and then it's gone. And it happens every outing now, and my routine is so regular, that I can almost pinpoint the spot on the lake where it will happen. It's like clockwork.
I read in another forum where a guy described a very similar situation. He made a video of his motor when it dies...this is his video, not mine, but the behavior and sound is nearly identical: https://youtu.be/f95tvwHS7g0
I thought it might be a warm-up issue, but it happened even when I let it warm up for about 20 minutes. My motor doesn't have a thermostat. Could it be a failing switchbox/power pack?
I'm stumped.
This is now a pattern, starting about 3 months ago: Starts easily and idles perfect at the launch ramp. Leave it running while I put my truck away, it's been idling 8-10 minutes by the time I'm ready. Another 4-5 minutes at no-wake speed. Power up to 50% or so, then after a few minutes of that...BAM! It starts to sputter and miss and lurch, then the RPMs quickly and steadily drop to idle level, even though I haven't touched the throttle. It doesn't shut off, it just powers down. Bringing the throttle back to neutral has no effect, pushing the throttle forward does nothing. It just coughs and sounds rough as hell for about 30 seconds. I turn off the ignition, restart it....maybe do that a couple of times. Same thing: throttle forward, nothing...sputters and misses.
Then, as if it just decided that's enough...it jumps out of the hole and away we go like nothing happened. For the rest of the day, whether it's an hour or six hours, zero issues. Smooth running, immediate starting, good hole shot, perfect.
It only does that weird thing ONCE, for 30 seconds or a minute, and then it's gone. And it happens every outing now, and my routine is so regular, that I can almost pinpoint the spot on the lake where it will happen. It's like clockwork.
I read in another forum where a guy described a very similar situation. He made a video of his motor when it dies...this is his video, not mine, but the behavior and sound is nearly identical: https://youtu.be/f95tvwHS7g0
I thought it might be a warm-up issue, but it happened even when I let it warm up for about 20 minutes. My motor doesn't have a thermostat. Could it be a failing switchbox/power pack?
I'm stumped.
