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Old 13 June 2011, 08:27   #1
Country: UK - England
Town: Padstow
Length: 4m +
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Posts: 9
Avon SR4 with twin 25hp?

i have a SR4 with a very old Johnson 40hp. I will need to replace at some point, and am thinking of going down the route of running a twin rig with 25hp 2strokes?
Has anyone done this before - is it a success or waste of money?
What is the performance like? Both top end and acceleration?
Will the transom take the weight?

Any advice will be most welcome.


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Old 13 June 2011, 08:30   #2
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Is the transom even wide enough?

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Old 13 June 2011, 08:55   #3
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Country: UK - England
Town: The wilds of Wiltshire
Boat name: WhiteNoise/Dominator
Make: Ballistic 7.8/SR5.4
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Personally I think it'll be too heavy, quite thirsty and cost more to do than stick a single engine on.

It'll probably need short shafts as well.
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Old 14 June 2011, 04:21   #4
Country: UK - Scotland
Boat name: Wildheart
Make: Humber/Delta Seasafe
Length: 5m +
Engine: Merc 60 Clamshell
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You may not be surprised to hear I did look into this before someone made me an offer I couldn't refuse for my old SR4 hull, and in summary I would have gone down the route, just not using twin Suz DT25s:

Yes, you'll need short shafts

Will they fit? - Depends if you have an A- frame and what engines you pick.

Weight - you will need to be very careful choosing your engines. Most 25s are around the 70-75 KG mark. Having said that, if you don't mind a bit of oldschool premix twin pot action, one that jumps to mind is the old Johnsorude 25 of the late 60s / early 70s which was a nice & light 38 KG or thereabouts. Noisy as, but light. And of course have you added the aux into the equation if you feel you need one.......

Usual stuff about the cost of two sets of remotes etc etc, but if you go pull start twin remotes with no keys etc probably won't be too much worse than a single with electrics. If you are buying new, cost wil lbe a lot more, secondhand will obviously depend what you find.

As for the drink like a fish, I doubt it. We're only talking 50Hp total here on a boat that weighs a couple of hundred kilos. Also if your 40 is as long in the tooth as you imply, I bet the difference in consumption is at best negligible. Smaller engines = smaller gearboxes = less drag.... Do a search for "twins drag".
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Old 27 June 2011, 14:44   #5
Country: UK - England
Town: Padstow
Length: 4m +
Join Date: Nov 2010
Posts: 9
9D280 - cheers for the info.
I have a solid 2004 merc 25hp so would just need to find another. i use the boat for as much as i can get away with - long cruising up the coast (sea state dependant) and wake boarding / mucking about in the waves. I would keep it simple - pull start, manual tilt so no battery which makes this easy.
does anyone know what the performance is like though, i am guessing pull out and onto the plane would be fine, just top end....?
i will check out the 'twins drag' info.
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Old 27 June 2011, 14:49   #6
Country: UK - England
Town: Mighty Penryn
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Make: Avon Searider
Length: 4m +
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Sell the 25 and buy a nice 50.
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Old 27 June 2011, 17:55   #7
Country: UK - Wales
Town: West Wales
Make: Vipermax 5.8, SR4.7
Length: 5m +
Engine: 150 Opti, F50EFi
Join Date: Sep 2005
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Originally Posted by Mollers View Post
Sell the 25 and buy a nice 50.

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