@TR. and @ROSC
It sounds like a similar experience. I got on the boat knowing one engine was acting up. It ran fine up until about Iceberg, then it would surge from our cruising RPM of 2800, down to about 1800. Tried changing fuel filters and no better. Kept doing that until we stopped in the main channel around Escalante and changed the fuel pump.
Not sure why, but that seemed to solve our problem. For a while. Until we got to about the mouth of the SJ, then both engines started doing it.
We ran about 8 miles up the SJ, and both engines died. For about an hour we messed with the fuel system. Luckily there wasn't much "W", but we still had to hook a ski boat up to the hotel to keep it in the main channel.
After a while, I got one engine back up, so we motored back towards the mouth and found a spot.
Did a bunch of troubleshooting on the dead engine, to no avail, so I knew for most of the trip we would be limping back on one engine.
That one did fine until about Hole in the Rock, then started acting up. We went from being able to cruise at 2800 RPM to 2500 RPM to 2000 RPM. Then everything went down at about Halls. The short version is that it took me 2 hours to go from about the Halls boat ramp, back to our slip. I finally got the engine started, and idled in. Again, lucky there was no "W" that afternoon.
I was one more stall away from calling Exec for a tow back in.
We think it might be the anti siphon valves as well. But I am not sure. Just glad that I got the boat back to the slip.
But I don't want to focus on that, because we had a great time.
I would post some more photos, but I fear that I will upset the internet police because some might involve activities that they would not approve of.....