Originally Posted by r mcdonald
One thought, If you were flying over a mountainous area in a light aircraft and the engine failed would you rather another engine on the other wing be the same size or a little aux instead.
I think your argument counts in favour of single engine vehicles...
There are many single engine planes around and they rely on their engine not only for thrust but also to stay up, if your RIB's engine also kept you afloat would you need two?
Planes with one engine are maintained like their pilot's life depends on it, why not apply that thoroughness to a boat?
If a twin engine plane suffers unrecoverable engine failure it becomes an emergency, this is not always the case with boats but I think it mostly should be (see my previous post on this topic).
All of that said there is a local twin outboard boat that can quite happily get around on one, so much so I have suggested to the owner that he gets rid of the redundant one!
He will go about as fast as he currently cruises and half his running costs. The boat used to go out in all weathers and work close in to rocks with 6 knot tides running, so the twin installation was a good idea.