Re: trim/tilt problem
Just had similar problem with 1999 Four Winns (5.7 Gsi). When I pressed trim switch, engine shutoff and 12.5 amp breaker (controls fuel pump) would trip. Occasionally, the 50 amp trim/tilt breaker would also trip.
This problem occurred 2 years ago and marina replaced breaker, but didn't solve the root cause. Problem would manifest itself intermittently, usually during high humidity conditions (in salt water morning fog or after heavy rain).
Was testing various components with multimeter and in the process turning battery switch on and off. Finally, happened to be near fuel pump, ignition off and turned on battery switch and heard fuel pump energize. One of those Ah Ha moments!
Pulled cover off of breaker box (bracket mounted on starboard exhaust riser) and found that insulated spade connector for output side of 50 amp tilt/trim breaker was rotated tight against insulated spade connector for output lug of 12.5 amp breaker. Couldn't see anything, but when I removed lug nut and checked spade connectors, insulation had worn through on both connectors where they were touching. Used liquid insulation to repair and carefully held connector to prevent rotation against other breaker connector when retightening.
This situation also caused battery rundown when I would forget to turn off battery switch when on trailer or when left on to run bilge pump while docked in water.
Since short had an air gap distance of worn insulation (3-5 mm), problem would only manifest itself when humidity was high enough to bridge gap.
Not sure of your breaker configuration, but start checking there and move back through tilt / trim wiring in harness whereever it may touch ignition/fuel pump/ecm wires.
Hope this helps!