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Old 24 June 2008, 11:45   #11
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Country: UK - Scotland
Boat name: Wildheart
Make: Humber/Delta Seasafe
Length: 5m +
Engine: Merc 60 Clamshell
MMSI: 235068449
Join Date: Apr 2007
Posts: 4,610
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Originally Posted by badbaws View Post
If going 40hp get a 3 cylinder model.. not a 2 cylinder model.. More grunt!
...but also more weight!!!!

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Originally Posted by reinier View Post
I know someone who had an Avon 4 meter with a Mercury 25hp Tiller steering, ran 34mph with two adults... A console slows the boat down very much as you can see.
Yep, Used a tiller 30 on an SR4 with nothing but a fuel tank & 2 of us. No idea how fast, but was a mentally fun ride, -can turn a lot sharper with a tiller than a wheel!
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Old 24 June 2008, 12:04   #12
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Country: UK - England
Town: Bristol
Make: Honwave T35AE
Length: 3m +
Engine: Tohatsu 18hp
Join Date: Feb 2006
Posts: 374
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Originally Posted by badbaws View Post
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.
I know the hull design is not supposed to have changed since they were first made in 1967 but have there been any slight changes to the exterior hull or tubes that could account for different perfomance results?

Some also claim to get issues with chine walking just after 30knts but others say they get no problems up to 40knts. I'm still running mine in after an engine rebuild but it was solid at 33knts.

I know that incorrect engine height, trim level, console position, load positioning etc. can cause premature chine walking but assuming all these are correct is it possible that slight changes to hull design could be the reason for varying results?
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Old 25 June 2008, 17:19   #13
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Country: Netherlands
Town: Holland
Make: Brig F360S
Length: 3m +
Engine: Yamaha 70hp
Join Date: Jan 2008
Posts: 85
Quote:
Originally Posted by badbaws View Post
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.

BTW:
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
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