Originally Posted by malthouse
One option suggested was a pair of 15HP four strokes, ok so long as the block is one of the bigger ones.
? twin engines only about 70% efficient as a single with the combined HP, so a pair of 15s will give you little over the equivalent of a single 20HP. Then it will probably weigh more, and have double the maintainence costs etc. Thats also assuming you have space for them on the transom. Unless you need the backup of having twins, or the extra manouverability then I don't think it is sensible.
Might make a difference what its for. E.g. if it for a workboat shunting yachts round a harbour that needs lots of grunt but not much top speed or if its for a safety boat that will spend its life ticking over but occassionally might need to go flat out.
Is it being used commercially? - because then I think who offers the best commercial warranty will matter. What sort of hours will it do? An ETEC with 300 hour service intervals might be attractive compared to a 4-str with 100 hours.
In terms of cost I'm not sure if buying new that there is a huge amount in it (~10% of value), and your ability to get servicing/help if needed is probably more important for a boat that is needed every day.