You might look up the specs on your boat and find out what it weighed. Then you can get a general idea of how much the trailer weighs, take it to a scale and see if it's packing a bunch extra. That's probably the best way to ballpark it. Without having to drill and patch holes.
Didn't get a chance to weigh as I was working on the fricking gimbal bearing! I will open another thread for that fiasco.
However, The weight is questionable as an issue unless someone knows different. This is because I did some exploratory drilling. No oil I'm afraid, so the Saudis are still in luck.
What I found is slight dampness.
There was no water to speak of, right to the glass. It was humid at best.
Basically, the boat was kept outside for at least 7 winters. Although, the bow end of the trailer was jacked up about 4 feet to keep a sharp decline to the stern. Plus the plug was out the whole time.
This situation might have helped because it never had standing water on the carpet or in the bilge because the water had to flow fast downhill, rather than find it's way meandering through the boat.
I drilled at the very back by the transom where the water would have concentrated (also where it is easy to simply patch the holes and not worry about looks because nobody can see or go there. Like I said, humid. Not a drop of water, just moisture. I know this is still not an ideal situation, but it is far from "Oh my god, what am I going to do now!". I really don't think that amount of moisture can weigh enough to lose 1000 rpm at WOT. At best, let's call is 35 pounds and I think even that is a stretch. I think to be so heavy to lose that much rpm due to weight we would be talking 600 pounds but that's just a guess.
interesting article from boatingmag :
https://www.boatingmag.com/packing-on-pounds#page-10
I do believe weight has a lot to do with out of the hole acceleration and even top speed, especially when dramatically overloaded though as I have had that experience having to ferry 7 people with my 70hp evinrude in an old glasply. But in reality, that was a huge load of about 1200 pounds plus I would guess. We never got more than 12-14 mph.
I still need a water test after my latest carb fussing. However, that has to wait until I get that damn gimbal bearing out (again, different thread).