I have a 2001 Launch (direct drive) and have had wiring problems as well. Speedo (Faria Electronic Gauges) problems appeared to be inadequate ground. Tach also read high periodically. Finally ran separate ground wire from speedos and tach to battery negative. Seemed to correct high/low readings, then had an actual speedo gauge failure and replaced with PerfectPass. No problems with that in 5 years and the best skiing I've had. Needed to replace the starter key switch as well. Accessories worked, but dead on starter mode.

Also, check your battery terminals and all cable connections at battery(s) and engine connection points. Any corrosion or looseness can cause the same problems. Disconnect and clean each connection before each summer. Retighten and coat with some battery terminal sealant.