Is better to adjust the float level wile in the water or on the trailer. The boat sits more level on the trailer like when it is plaining at a higher speed. When in the water at idle with bow up and the stern is down. where is the adjustment needed

Best place is in the water. Even on plane , the bow is up a little.
Although , mine were done when the engines were on a dyno and they worked fine in the water

In the water. If you set them on the trailer, they could be too high. This could cause excess fuel to drip into the carb at idle and cause a rich condition.

ttt

I would set the float levels as the boat sits on the trailer ( same as on plane )... you can check the float level while the boat is idleing in the water... if you have electric fuel pumps.. you can do it without starting the engine...if you have mechanical pumps... you have to check while the engine is running... either way... just look down the throat of the venturi and see if there is gas dripping from the boost ring ( auxiliary venturi ).. if it is dripping... then the float level is too high... good luck.