Success! I made a duplicate of the last example with the 5/16" rod and the end flattened on 2 sides with a bench grinder. It went in first try. The only helpful hint I’d add for anyone reading this afterward was the grommet went in but the tabs were not lined up with the holes on the side. When I looked into the inside hole of the grommet I could see the shape of the grommet was oval with the tabs bulging in… the quick solution there was to take a screwdriver that was just small enough to fit into the hole inside the grommet and then rotate the screwdriver to turn the grommet until the tabs lined up and fell into place. Many thanks everyone.
That water passage where that grommet goes in, likes to corrode shut, on salt water motors, so rod it through and make sure it’s clear. I’ve had to clean a couple out through the years. It wouldn’t hurt to check and make sure the grommet area is free of corrosion too.
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