I installed a pair of 3116 cats in a 32 blackfin 3 years ago , a real shoe horn job(had the whole boat apart) since the tank goes down
between the 2 engines and the water tank
takes all the space under the cabin , the only usable space left was the fishwell in the stern (Bad idea) So we
instead chose to go the 12 volt route and take along a honda pull start for emergency.
Also we installed 4 giant cat 8D batteries 2 ea side(tried hard to run them dead on overnighters but they held up)The TV VCR stereo fridge and water heater all 12 volt.
Stove is alchohol and there is a bbq.
I am going to replace the 8D's this year
as a good measure deal.