I have an older boat also, 1990, and I have experienced various poor
connections. Anything that is just crimped on probably has developed
resistance. I have also found that even those multi-connect rubber
plugs can develop corrosion and resistance after a long time. At one
point I was getting about 8 volts at the hot wire to my ignition.
Testing with a voltmeter shows various small voltage drops at
connections. The external appearance of any connection is no
indication. Same for the battery terminals. You need to take it apart
and wire brush the metal where the two meet. I removed some
connections and simply soldered the wires together and covered them
with heat shrink. Others I cleaned. On wire connections to terminals
and bolts I added stainless steel inside star lock washers. These have
teeth inside the washer and the teeth bite into the lug. Particularly
where main power wires were.

msd47 wrote:
I have a 1989 Wellcraft I/O powered by a 3.0 Mercruiser. I am having
intermittent electrical problems. Sometimes the motor doesn't crank,
and sometimes after it starts the tilt/trim control doesn't work. At
other times starter works fine as does tilt/trim (repeated efforts to
start ot raise/lower unit meet with success). I wonder about battery
cable connex and also a faulty voltage reg. Anyone have any other
ideas?

msd47