Glad you got to run your motor,(hope it was in the lake:D )& not on them hose pipe connectors.The high speed miss could be in the Carb-If the boat has been setting up any lenth of time.The Jets in the carb- are small & it don't take much to plug them up,ol'gas & oil mix will tarnish.
As far as the depth finder,No there is not much you can do out of the water.