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Old 12 July 2004, 07:35   #1
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Country: UK - Scotland
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Twins

I'm about to double the hp of my Northcraft 5.4 by installing another Yam 55.
Questions; How difficult would it be to have the new engine turning opposite to the existing? Can you get left handed props for a Yam 55? Is it worth the effort or can the extra turning force be trimmed out?

Ian
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Old 12 July 2004, 08:00   #2
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Ian,
Normally on an outboard you need to change the bottom leg to get the oposite rotation.
If you are looking at uping he available HP it might be more economical to move up to a 70 or 90, as you don't get the sum of the two outboards hp in a dual set up more like 3/4 of the sum.
There have been many threads on the decision of dual or larger single.
Rgds
James
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Old 12 July 2004, 14:09   #3
TIM
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ON a 55 hp, you wouldnt notice that the props arent counter rotation, you need to be getting into the 100 hp and up bracket to notice...

TG
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Old 12 July 2004, 14:41   #4
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You are not going to get counter rotation on anything below 135
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Old 12 July 2004, 14:56   #5
tue
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IMHO its not realy worth the agro of chopping bits off transom to make 2 motors fit and then connecting them. Your best bet is to go bigger. Maybe a new 90 or 115 optimax
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Old 12 July 2004, 16:20   #6
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Ian

I would only have twins if I had
1) Twin Tanks
2) Twin Batteries
3) All controls were totally independant.

Why do you want to add extra HP? is it purely for speed or safety?
Remember extra fuel to carry, double service costs etc.
I would say go for a single larger engine and perhaps a small auxiliary for back up.
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Old 12 July 2004, 16:40   #7
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twins

I would only have twins if they were from the Ukraine blond and in their late twenties
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Old 13 July 2004, 02:26   #8
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Many thanks for the info and advice. My main reason for movng to a twin setup is for safety - I tend to feel a bit vulnerable with a single engine playing on my own in the North sea outside Peterhead harbour. Another advantage of having an engine either side of the transon is that I won't have to cut to to fit as a long shaft has clear water away from the centre line.
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Old 13 July 2004, 07:44   #9
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With todays engines being so reliable i just wouldn't have twins.
Your going to cut your range in half which wont allow you much cruising range at all.
A new engine is a lot more expensive, but when you add in the service charges for 2 engines, fuel for 2, oil for 2 and the increased resale value paying the extra for a single new engine could be well worth it.
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Old 13 July 2004, 08:05   #10
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whilst on the subject of twins how much better performance would you get on an 8.5m rib if you added a second 225? or would ONE 300hp be better?

I know top speed wouldnt be much better but what about acceleration after hitting a stopper etc?
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Old 13 July 2004, 08:40   #11
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I have also been advised that with twins because they are usually proped differently to a single, if one fails and your running on the other the performance is much worst that if that same engine was set up as a single. I have even heard rumours about them struggling to get on the plane on one engine !
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Old 13 July 2004, 13:33   #12
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Twins

I think we have given this one a good airing in the past. But as a quick note.

1. Twins will always provide better stability to the vessel. Look at a transom elevation put a single on and compare the fulcrum to a single.

2. For performance the single will give better.

3. Set up well, a pair of twins WILL NOT use more fuel than a single.

4. If one engine goes down the second may well not get the vessel on the plane but should provide a good 10knots which is much better than a 5hp aux which will give only a couple of knots.

5. The manouverabilty on a well set up pair of twins is superb when used correctly.

6. Twins may be seen as a lux but for those who have used the set up they will never go back to a single.

7. Agreed that it is the servicing of two engines but with a good dealer they will price according to volume.

And on the point of twins

1. All of our vsls are twins.
2. We have 6 kids - including two sets of twins so a tad of bias !!

Cheers

John
www.quinquari.co.uk
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