Thanks guys for your input, sorry i'm late replying and I forgot to give HP of outboard which is 115. As the price of fuel here in NZ makes this old timer want to cry each time I fill up, i'm trying to economise! I remember someone on a forum saying that if a classic two stroke like a 2x2 115 is just ticking over, and no more, their not to bad on the gravy. I find if I run my 15HP aux.or kicker at approx. half speed with the slow pusher prop fitted,and the 115 just ticking over, I get approxamately 5-6 knots on my 18' vairable V boat with good steerage thrown in. I'm even thinking off harnessing a heavy pull single line fishing kite on the downwind runs when time is not that much of a priority, ha ha! Get a life and a diesel launch do I hear you say?