Originally Posted by badbaws
If you have the standard avon Console it only weighs about 20 kg or so, as is thin and quite small and it also moves the weight of the driver and one passenger to the centre of the boat for best weight distribution rather than perched on the back. With a brand new Tohatsu 50 last summer I got 33.2 knots maximum with 1 person, 31 knots with 2 people and 30 knots with 3 people.
I think it needed a different prop to get a couple more knots out of it.. but pretty much with a 50hp the most you are going to get is about 35knots +/_ a knot...
If you are getting anywhere near 30 knots with a 25hp you must have the best 25hp ever.. as last one I saw with a 25hp managed about 23 knots..
Also it depends how you measure your speed, GPS up and down wind and up and down tide.. but most I have ever achieved in a 4m searider is 37 knots with a 1992 Mariner 60HP 3 cylinder engine.
Well it's not mine, that Avon with 25hp. First I didn't believe it as well, but then the guy took me out for a ride and it really hits 34 mph, with two adults. This was on flat calm water, both directions (there wasn't any tide). Adding more horsepower isn't always expressed in much more speed.
I had a Brig F360 with a tiller steered 40hp, so 3,6 meters, almost as long as the Avon we're talking about. Once there was a 25hp on it. Hitted 37mph with the 25hp, right prop and not too much load. With a tiller steered 40hp, she reached 40mph. That's a gain of 3mph in first instance. A bit later I used a bigger prop on the 40hp and with lot's of efford in testing engine mounting heights etc. I achieved 44mph.
There's an Avon with a 2-stroke 60hp Mercury 3 cilinder @ the lake here, I always wondered how fast that goes... Thanks for sharing :P