Glad you got it back on the water.
I have OT headers so I don’t know much about logs and snails. But, it with the “slow” temp climb, it seems you’re not getting enough water through it (obvious right

).
If it’s not a blockage, and not pre-heating the water, I would probably start with the pressure relief. maybe it’s letting out to much water? Maybe raise the pressure it opens at. Or you might not need it at all. A lot of boats run without them.
If that doesn’t help, maybe look into bigger inlet lines. There has been a few threads about plumbing and I think most responses were at least a -10 supply line.
Just make one change at a time.
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