The electrical power distribution wiring and lighting control circuits on c.1988 Boston Whaler boats are typically quite simple and not particularly complex or elaborate. To find a source for an OEM harness for your particular model for the wiring is unlikely. It should not be too hard to fabricate new wiring using quality components.
As for getting access to electrical panels in your c.1988 Boston Whaler boat, if you are stumped try contacting Boston Whaler customer service. Old hands like Chuck Bennett will be very familiar with your c.1988 boat and can help you understand how it was constructed.
Some of the helm electrical panels made from aluminum were fabricated for Boston Whaler by a contractor. See
http://continuouswave.com/whaler/refere ... helmPanelsIt is not too difficult to fabricate your own new panels using aluminum plate material. Many aluminum distributors have cutting shears and can cut simple rectangular shapes for you.
For some remarks on refurbishment of the electrical power distribution on my c.1990 Boston Whaler boat, see
http://continuouswave.com/ubb/Forum6/HTML/003179.html