25hp 2stroke 1996 model

[Chippies]

I have a few questions regarding my 2 x 25hp 2-stroke 1996 model, pull start outboards that are powering my houseboat. Can you tell me the correct 2-stroke oil mixture, are they easily compatible with charging units and what current would they charge at? What type of props would be most suitable to push a 6ton houseboat at low speeds? Can you still purchase cowlings for them or do i need to chase up 2nd hand one's?
Regards

[boats.net]

If they are C25 model motors then oil ratio is 100:1 and have 6 amp alternator but need to to install 6G1-81970-00-00 rectifier kit to charge battery.
Need to use the smallest pitch prop you can find like Yamaha's 6J8-W4591-00-EL 10 5/8 x 8 1/4 al prop