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Old 04 March 2009, 03:35   #1
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Old spinner

I don't know if this a motor or boat issue but when I put the motor on my Avon s300 into reverse the boat just spins around in circles. Try counter steering but it still makes circles. The motor is a 1976 25hp Evinrude. I do find the boat is not very manoeuvrable at slow speed so my monay is on the boat being the problem.

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Adrian
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Old 04 March 2009, 05:52   #2
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most inflatables dont reverse very well and a lot are not that manouverable at slow speeds anyhow , it could be the pitch on the prop is high, if it goes ok ahead i wouldent fuss too much , alot depends on how much keel at the bow you have ,when in reverse it will tend to act as a rudder, with no keel will tend to skate about even more , regards mart
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Old 04 March 2009, 07:18   #3
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I notice it at tickover on mine. Have assumed it was a form of "paddlewheel effect"

Generally find that more manouverable at low speed if you give quick blasts of "power" rather than trying to turn at tick over speeds.when in reverse an o/board prop is driving through "gas" from the exhaust - so is pretty rubbish. the engine isn't a very good rudder - so only changes direction easily if it has "thrust" in the required direction.
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Old 04 March 2009, 11:22   #4
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When powering forward (talking low speed here), most outboard powered boats tend to pivot around a point about a quarter to a third of the way back from the bow.

When reversing, they tend to pivot around a point much further back, maybe a quarter of the way forwards from the transom. Makes it seem like it steers much quicker going backwards, though it's usually not, due to prop inefficiency.

Boats with little deadrise (like most SIBs) are worse as the hull skates over the surface rather than exerting any kind of drag to keep the boat following the keel line.

Just my opinion;

jky
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Old 04 March 2009, 17:48   #5
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Quote:
Originally Posted by jyasaki View Post
When powering forward (talking low speed here), most outboard powered boats tend to pivot around a point about a quarter to a third of the way back from the bow.

When reversing, they tend to pivot around a point much further back, maybe a quarter of the way forwards from the transom. Makes it seem like it steers much quicker going backwards, though it's usually not, due to prop inefficiency.

Boats with little deadrise (like most SIBs) are worse as the hull skates over the surface rather than exerting any kind of drag to keep the boat following the keel line.

Just my opinion;

jky
Jky - all valid points - but I think the OP was describing a situation where the boat turns one way but not the other in reverse (or one way much harder).
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Old 04 March 2009, 21:55   #6
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I think you nailed it Jky.
Good descripton and makes a lot of sense. So if I was to drop a lee board (oar) off the side then it might make a difference when going backwards.

Adrian
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Old 05 March 2009, 11:46   #7
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Backing a flat bottom boat can be tricky. They tend to resond to thrust only in general direction, and often with no kind of orientation. Wind and current will have a huge effect; you sometimes will find yourself going in the direction you want, but sideways.

What I used to do, was to use quick bursts of power to get the boat oriented the way I wanted: For example, if I was backing up to the south, and the boat started pointing (not drifting) more to the west as it traveled, you'd turn the motor to the west (or southwest, at least as much as possible)and give it a sharp bit of thrust to bring the nose back in line. It does tend to pull you off line, but it keeps the boat pointing the way you want. Usefulness depends, of course, on how much room you have to work with.

Hope this helps;

jky
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