Re: 25 hp a/c output
Yes absolutely doable and several ways of doing it.
1. Get the battery charging kit for models with an AC lighting output. Part number 0582105 (price $77.91 USD). Essentially a rectifier and wiring harness which plugs into the AC socket.
2. Get the rectifier part number 0581778 ($49.96 USD), or a cheaper equivalent from Sierra etc, and the terminal block, all the screws (0511949 and 4 off 0329182) and a few other minor bits and pieces. Doing this you then have the rectifier under the cover and mounted as it would be on the electric start models. The DC output goes to the battery connection on the starter solenoid.
3. If you have the electronics know-how build yourself a 3 phase bridge rectifier using six suitably rated diodes from your favorite electronics component supplier. This of course is the cheapskates solution.
See the lower diagram below.
You can find all the above mentioned parts by going to the parts catalog
HERE and finding your engine. The rectifier and terminal block are on the "Ignition" diagram, #6 and #4.
To find the battery charging kit select "OB accessories" from the drop down list (not the accessories tab), select 1985 and then "electrical".
Diagram referred to above:
