No gauge needed
When on the hole shot, drive all the way down, as you mash the throttle and the boat comes out of the hole and starts to settle down......thumb up on the trim until you start to get porpoising. Than tap it down a bit until it settles. You will feel the boat pick up speed
If...
I dont think i ever trimmed up that high with any Mercruiser . i think about 1/4 on the gauge is all that I ever did unless there were a lot of people up in the bow.
while they are on the spare bed. lay the parts out and place a beach towel between teh 3 pieces - making a big "club sandwich" so to speak. then roll them up and put in one of the folding camp chair bags. https://www.amazon.com/s?k=folding+camp+chair+bag
then secure in your head in the corner.
