Maybe you're having a problem with steam getting sucked up into the intake. I don't know if the 420 Rancher had a problem with that or not, but Yamaha had a problem with the early Grizzly models, because of those plastic panels that cover the engine on each side. When you would go through water, steam would get trapped in the engine area and couldn't get out because of those panels. The steam would get sucked into the intake and the engine would sputter and die. They fixed the problem by putting vent holes or slots in the panels so the steam could escape. I don't know if that would be a problem on the 420 or not, but they have those engine covers. Just a thought.
You might pull those panels off and try going through water and see if it helps. If that's not the problem, I don't know what would be wrong, since you've already put dielectric grease on all the connections.
You might pull those panels off and try going through water and see if it helps. If that's not the problem, I don't know what would be wrong, since you've already put dielectric grease on all the connections.
