"Robert, first off - sorry, th
"Robert, first off - sorry, this got a little long
To change the impeller I suggest you pick up a Clymers manual covering your motor. I'm not trying to cop out here, but the 85 Force is one of the biggest "mongrels" of the outboard world.
In 1988 alone there were 40 distinctly different models of the 85 horse Force - all with different parts (to an extent great enough that they got a different model number).
Why? Force was originally Chrysler Outboard. Bayliner bought them out when they went bankrupt, gave them to their US Marine division and basically continued to build Chrysler outboards under the new name "Force".
A couple years after that, Brunswick bought out
Bayliner and gave the Force line to Merc (who they also owned).
Merc continued to produce the Force line for about 10 more years. Initially the motors were still pretty much a Chrysler, but as they started running out of parts discontinued Merc stock started to get used as well.
In the last few years of production it was a case of "make it fit" and if it worked they produced that model until they ran out of parts - then grabbed something else off the shelf. If that worked then out came a "different model" - so in 1988 that happened 40 times with the 85 horse.
Because of that you need to find your model number and service exactly to that model because even if "joe next door" has the same model year 85 horse Force, it may look nothing like yours when you take off the hood....
As to repairing the floor. Normally you will remove all the rotted/destroyed fiberglass and plywood and replace with similar materials. If you have a West Marine close by, stop in and pick up a little booklet produced by West System. It's called "Fieberglass Boat Repair and Maintenance" (sells for about 5 bucks I think - or check out the West System website - nothing to do with West Marine, West System wrote the bible on epoxy/fiberglass).
It's about 80 pages and shows you all what is involved in doing the repair. From that you can decide if you want to undertake the project in that manner.
Alternately, the floor can be replaced with a product such as "Starboard" (similar products sold under serveral names) which is a type of plastic used extensively in the marine industry today. It is pretty much used the same way as plywood (and cuts/machines the same as wood) except you don't need to epoxy or fiberglass the product which doesn't rot and needs no further protection when used right off the shelf.
Starboard however, can not be glued in place (nothing sticks to it worth a damn) so mechanical fasteners are a must (usually high grade stainless) and it can not be painted, so you are stuck with the minimal colour selection available.
And in and of itself because of the way it must be fastened it is not a great structural material, so you need extensive "more traditional" framework in any area that needs the strength to ensure the structural integrity of the boat (on the average boat that would be the athwartship supports (from one side to the other on the hull upon which the floor or "sole" sits) which keep the hull from twisting and flexing
In the end, both methods cost about the same (depending on supply sources local to you).
The Starboard may be somewhat less labour intensive (since framing must be done for both methods) but the epoxy/fiberglass/plywood method will give you a more original look - so it's kinda a matter of personal taste.
I have used both (aside from working on outboards and doing rigging I build wooden boats, and do repairs to a lesser extent on fiberglass as well)and which product to use is always on a case by case basis...."