It seems to me that a reality check is usefull here. Like always it is firemost important to determine what you will use your cat for, wgere, how?
Serious long range cruisers won't choose outboards to propel their cruising yacht. To carry more petrol than you need for your
dinghy outboard is simply very irresponsible. I have a secure dedicated petrol (for
dinghy outboard) locker that drains between the hulls st the stern of my cat. Wgere would I store more petrol. Outboards propelling the cat would consume much more than your dinghy outboard. Where on a small, under 36 foot cat would you store that extea petrol.
If that is not a serious enough argument against outboards to propel a
multihull think of the
battery charging. It is one of the most important issues for a long term long range, of the beaten track, far from popular, tourist infested , cruiser.
Cruisers spend lots of time on the hook out of
marinas the marine diesel engine has to run regularly to keep it in good condition, the non-load running can harm the engine but with the lias of a few Hp because of high rated alternators resolves this.
The dragging of the inboard propellers is a non-issue amongst the cruisers. Foldi g propellers are a gimmick. To keep them free from marine growth is extremely difficult. They will stop folding ir unfolding with just a bit of marne growth, and we cannot anti-foul them.
Inboards can be located in very difficult to reach bilges under
cabin berths. I would not go for
multihull where you sleep on top of engine, where diesel smell cannot be eliminated, where engine
noise, vibration affects you. On my 34foot
Catalac inboards are in spacious stern lockers reached from the
cockpit.
Cruisers know that working on outboards is challenging because of the fine mechanical design. If you
service, change all filters, oil, use anti-freeze in your engine
coolant, make sure your through bhull seacocks are in good condition and valve closes Inboard diesels basically will keep going if you give them clean water free diesel, simple baya filter will help there and discipline handling the fuel.
Hobbyhorsing of any multihull in heavy seas will affect your outboards. Some are designed to run even when submerged but we all kniw it will only be matter of time before damage occurs. The position of the outboard
propeller has tobe in the ideal drive position to be efficient, fuel and power wise. Only efficient o flat seas. Once up and down movement starts in the waves imagine the poor efficiency. Inboard propellers, typically on saildrives mounted far from stern in front of the rudders, will remain efficient even in heavy seas. The flow of water from the propellers will make the rudders,
steering, much more efficient to.
Autopilot on rudders used in combination with outboards simply dont wirk as smooth as they do with inboards.
Sure outboards will be best for the weekend cruiser because marine diesels have to run.