Another thing to consider Dave
Is to check out the Beneteau Owners Association, and look specifically for a sub group of the First 285 owners.
As a Catalina Owner, I can go to the owners association site and look up published information that is specific to my boat. There are usually people at those sites that are major contributors to those sites, like we have here. Those folks have a lot of experience with the specific model of boat that they own, and their interest in their boat has driven them to research, document and share everything that they can lay hands on. They are really tight with the factory folks and get lots of info from them and the design engineers.
Also, did you get an owners manual with your boat? There should be a routine set of maintenance guidelines for it. There should be a book specifically for the engine. Yanmar has one for mine with a page with routines to be done by the hours, oil change, impeller change, oil filter, fuel filter, belt tension for alternator, coolant, cleaning the rods out in the heat exchanger, valve lash adjustment, etc.
For the engine for instance, like Nice n Easy has said, maintenance...maintenance, etc., and then some more.
Check belt tension, change filters, flush the cooling system, change the coolant, keep fuel topped off, make sure fuel is treated with bio-guard, keep fuel treated with water-zorb and stabilizer, keep the impeller working good by changing it out, clean out the raw water intake strainer, check the motor mounts, check the alignment of the engine and the shaft, ensure it is less than about .03 inch of throw out or what ever is stated in your manual, keep the battery terminals clean, put dielectric compound on them, check all your electical connections for tightness and keep clean and corosion free, especially with the ship to shore power cord, again, dielectric compound and make sure the terminal lugs are tight from the twist lock to the main service disconnect for the boat, clean the filter for the fresh water pump, make sure your scuppers are opened up, check the bilge pump and float switch and ensure that they are kept clean and free of debris and no build up of slime. Do you have propane on board? Check the bottle, and make sure it is rust free, touch up if necessary with primer and paint. Check the tension on the shrouds and ensure the rigging is balanced. Pull the winches apart and clean and lubricate. Take a box like an empty beer case or similar in size and cut a hole in it the diameter of the largest diameter on the winch and place it over the winch and down on to the top of the boat so if you take the winch apart with the boat in the water, you don't loose anything. I do this if I don't get the boat hauled out and the winches need to be cleaned and lubed just to keep from dropping anything overboard.
YU know, just like Nice n Easy said, pre-flight check it. Turn your fire extinguishers upside down and beat the sediment out of the bottom with a rubber mallet and then invert them back and forth several times to keep the bi-carb mixed since it will settle to the bottom and pack down and not be mixed up when you need it if heaven forbid you ever do. Check the specific gravity of the battery acid with a hydrometer, you know, just the routine stuff.
Do you have packing or the PSS dripless seal for the shaft? Check that. Work the through hulls and put a little lube to them also. Look for any rust and eliminate it with some ospho and then prime and repaint.
You should be able to find something from the Beneteau site though that someone has put together on a spreadsheet. Also, check for a commissioning and decommissioning sheet for winterizing and bringing back online in the spring.
Good luck Dave.
Tom