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Old 13 September 2006, 15:59   #11
Country: UK - Wales
Town: swansea
Boat name: Too Blue
Length: 8m +
Engine: Suzuki DT225
Join Date: Mar 2004
Posts: 12,791
Originally Posted by Cracker
Is your engine off set and if so by how much
Yup many single engines are offset - mine is by a noticable amount.

Makes me wonder why there has only ever been 1 duoprop outboard(I think) - the Yamaha vmax 150.

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Old 13 September 2006, 16:31   #12
Country: Other
Town: Stanley, Falkland Is
Boat name: Seawolf
Make: Osprey Vipermax 5.8
Length: 5m +
Engine: Etec 150
Join Date: Mar 2006
Posts: 3,704
I would have thought a duoprop would be horrible with the downstream prop suffering from all sorts of odd turbulence effects off the trailing edges of the upstream prop, but I guess they work if people make them!

I've never measured my offset and its cold outside and I am sat down with a bottle of something so I'm not going to go and do it now, another day maybe

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Old 13 September 2006, 17:10   #13
Country: UK - England
Town: Aylesbury
Length: no boat
Join Date: Jul 2006
Posts: 345
I don't notice prop steer on mine either - but let it run on its own at high speed for long enough on a calm day and you will notice a gentle curve or the boat bank off to one side - not sure why it is worse on some boats that on others - but guess the torque at the prop has a lot to do with it - how much power you have and how much hull is in the wet stuff!

found the bit about Volvopenta inventing the duoprop...they say...

When Volvo Penta introduced the patented Duoprop in 1982, it was the biggest event in boating since the propeller was invented. Twin counter rotating propellers bite hard to produce unparalleled thrust, straight and true tracking – even in reverse – plus faster acceleration on the plane.

The counter rotating twin propellers eliminates the lateral forces existing in conventional single prop sterndrives. That means the engine’s energy and power is concentrated on driving the boat forward – not sideways

Straight tracking
Duoprop tracks straight. Check over the transom of any Duoprop powered boat. The evidence of cleaner, unruffled delivery of power is there in the wake.

Faster acceleration
Duoprop provides up to 30 % faster acceleration and produces a top speed some 5 % faster than any conventional single propeller system – without increasing the fuel consumption. At partial load you can expect between 10 and 12 % lower fuel consumption.

Faster planing
Better grip in the water means getting up and onto the plane faster. And staying there at lower revs.

Handling is better too
Whether at speed, round the buoys or when docking in a crowed marina. The grip is there – even when making sharp turns at high speeds. Duoprop also reduces the boats tendency to roll.

Lower vibration and noise levels
Duoprop produces lower vibration and noise levels due to the fact that the shock pulses are distributed over more blades. With its counter rotating propellers it’s almost cavitation free.

They don't mention its twice the cost when you hit something though!!!
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Old 13 September 2006, 21:29   #14
Cypman's Avatar
Country: UK - Isle of Man
Town: Douglas
Length: no boat
Join Date: Aug 2006
Posts: 337
Engine offset will often cure this problem, as will careful location of heavy items ie battery, spare fuel etc, A slightly offset console will also solve the problem.

I have the same boat as you with a Suzuki DF140 on the back. My engine is offset 1.5ins to the right and the dual console is 2ins to the right, the boat is well balanced as a result. However, I would not suggest you should try relocating your engine and/or console at this stage unless it is an easy fix but just live with the issue.
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Old 14 September 2006, 09:03   #15
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LURCHER's Avatar
Country: UK - England
Town: Tisted Hampshire
Boat name: Hot Lemon
Make: Scorpion
Length: 8m +
Engine: Yanmar diesel
MMSI: 235
Join Date: May 2002
Posts: 774
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I had the same with my Humber , a pronounced list when powering up , it appears that the engine was not fitted vertically by the previous owner so under power the engine made itself vertical and caused the boat to list. We had a new alloy plate fabricated to realign the engine and all is well now .The reason for the plate was that the transom had been hacked about to accomadate a short shaft engine in the past and so many holes drilled .Hope this helps .
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Old 18 September 2006, 08:52   #16
Country: UK - Scotland
Make: HumberOceanOffshore
Length: 8m +
Engine: Volvo KAD300/DPX
Join Date: Oct 2002
Posts: 5,045
Originally Posted by codprawn
...the new Volvo QLs would be great ..........I have a pair but haven't fitted them yet!!!

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