If you have the stock Weber carb Eldebrock makes one that you can use also. It's spring loaded. Great for boating in the air.

Umm just a little FYI you will never get a Holley to work right with a 45 degree angle. The front bowl will fill up then when your back level it only has one place to go, the engine. I would be more worried about braking the boat in half then a carb trouble. Fuel injection as mentioned is the only way u can get away with that much angle.....

Thanks for help guys ill play with float level