Off hand, I say you lost 400 rpm and ran out of motor because of the higher pitched prop..If your engine could still generate the 4800 rpm you would go faster..
Put recommended amount of oil in, the dip stick is a joke , if you don't have oil in the bilge and the motor is not pumping it out on the water your good.
I don't know your situation but couldn't you core it as far forward as possible and then run solid glass just for the edge that tucks under the forward section.?
When I had my bell housing off to replace all the rubber bits I forgot to tighten the screws on the sender and it slipped out of adjustment. Maybe yours has slipped.
