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Old 29 October 2010, 14:52   #1
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Pretty serious steering concern

Evening all, not sure of this is a common problem, or if it is related to the wrong prop or something, however, we have just bought a second hand rib (5.9m 90 4 stroke) and it has two pretty nasty traits:

1) If you let go of or loosen your grip, then the boat veers very sharpy to the right (either just before you get on the plane or whilst on the plane, but not so badly). If you play with the trim and trip up a bit, then it either doesn't do it or does it less. Any thoughts?
2) The prop cavitates really easilly, far too easilly i think.

Any ideas? Could they be linked?

Thanks

Fletch
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Old 29 October 2010, 16:54   #2
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Hi Fletch

Is it possible the outboard is not mounted correctly? ie, check to make sure it is firmly mounted, perfectly vertically and in a central position on the transom.

ALthough i have never experienced it, i would imagine an 'off center' outboard would put a certain amout of torque on the hull making it want to veer off.

Also, does the prop cavitate more when the outboard is trimmed up slightly?

Simon
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Old 29 October 2010, 17:48   #3
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Have you checked that the small zinc trim tab under the cavitation plate is set at an angle to offset the turn?

Whenever this is serviced it needs to be replaced in the same position.

just a thought.

davej
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Old 30 October 2010, 06:15   #4
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I would say that 1) is normal for cable steering, to get rid of that you will need no feedback or hydraulic steering - as mentioned by others it can be reduced but you will always get feedback at certain trim angles.

Cavitation will be a factor of engine height, prop and throttle setting, see if you can borrow a different prop off someone with a similar setup to yours.
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Old 30 October 2010, 06:20   #5
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Originally Posted by Anchorhandler View Post

ALthough i have never experienced it, i would imagine an 'off center' outboard would put a certain amout of torque on the hull making it want to veer off.
Jigsaw has an "off centRE" outboard
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Old 30 October 2010, 06:40   #6
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Quote:
Originally Posted by Anchorhandler View Post
Is it possible the outboard is not mounted correctly? ie, check to make sure it is firmly mounted, perfectly vertically and in a central position on the transom.

ALthough i have never experienced it, i would imagine an 'off center' outboard would put a certain amout of torque on the hull making it want to veer off.
Unless I have misunderstood I thought nearly all outboards of any size were mounted slightly off centre to counter the torque reaction? The E-Tec on my Vmax certainly is. Also gives an inch or two more space for the aux engine as an added bonus
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Old 30 October 2010, 07:12   #7
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Jigsaw has an "off centRE" outboard
Ok, where is the emoticon for 'embarassed' when you need it?

Perhaps his outboard is offset to the wrong side then?

Simon
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Old 31 October 2010, 04:07   #8
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Thanks all. I have not played with the trim tab, but i would expect that it would do exactly that, i.e. trim rather than prevent pretty sharp turns. Will have a go anyway.

Thanks for the input

Fletch
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Old 31 October 2010, 15:00   #9
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engine to high i would think
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Old 31 October 2010, 16:55   #10
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are you talking ventilation or cavitation ? it's two different things and requires different actions.

Ventilation is air being sucked down due to bad trim or mounting of the engine.
Cavitatation has much more to do with the propeller design (vapors around the blades due to high pressure).

Cavitation can potentially damage your prop over time. Ventilation courses bad turning capabilities, acceleration and so on...
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