I have an 18 foot space sailer and use a 5 hp longshaft Tohatsu. I generally sail between Perth and Rottnest (about 12 miles each way)

It depends on what you want to use the boat for, if you are doing a bit of coastal cruising anything less then 5 hp is a bit small for pushing into the wind when entering bays or going aganist the tide through Swan River Bridges

I had a 3.5hp that was perfect for the river but struggled in the ocean.

Hope that helps

karl69 said...

I thinking of putting a new out board on my 6m Redwitch. I like the little Honda 2.3hp four strock because they are lite and air cooled so you dont have to flush them out or worry about replacing impellars ect, but i am not sure if 2.3HP will be big enought. Just like to here any opinions on what size out boards others are using and on what size boats .
Cheers Karl.

My yacht tender is a Windrush 14 with a plywood deck/cockpit. Propulsion is by oars or a 2.5 hp Tohatsu uprated to 3.5. I can lift the motor over my head with one hand easily. The uprating is done with simple changes to the carburetor.

A two stroke engine will be much lighter and safer to store if you remove the engine off the bracket, 4 strokes have to be laid down one side only. The Tohatsu in the smaller sizes is also sold as Mercury or Nissan in some markets. A 3.5 Nissan has crossed the Atlantic non stop.
Couple of points. Small motors will usually have integral fuel tanks. Small yachts don't like weight over the stern. Small yachts with outboards on the stern are hopeless motoring in a slop, you will always be better off sailing and using the motor only to return to a mooring etc. The Tohatsu 5 that Ky mentions would be more than capable in your case.

I have a 2hp honda and it pushes my boat great.Even does 4.5 knots in reverse!! But i imagine she is a lot lighter than a redwitch.And its pretty noisy being air cooled.And i find it doesnt like being layed on its side at all.even the correct way.I think 5hp at the bare min.My boat is a waller 5.4.