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Old 01 March 2013, 18:40   #1
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Country: UK - England
Town: Bristol
Boat name: loopy lou
Make: Avon Searider
Length: 5m +
Engine: Honda BF75
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Avon unstable at speed

Hi All
I need a little help with my new acquisition a 5.4m Avon Searider with the flooding hull sealed and a Honda BF75 hung on the back.
I took the boat out today for the first time and was pleasantly surprised with how quick it got to plane but it was very twitchy at 30+ .
It felt like it was perched on a peak and was just waiting to fall off , A couple of times I had to pull the throttle back sharply or it felt like I was going to flip over sideways.
Is this normal with deep v hulled ribs, I have never had this with my little caribe rib and I am often flying around at 35+ with no problems.

All help welcome
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Old 01 March 2013, 18:46   #2
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This should be interesting. Someone daring to suggest a Searider might be unstable. My guess is it must be a Chinese copy ;-)
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Old 01 March 2013, 19:25   #3
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Country: UK - England
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Boat name: Marty
Make: Avon Searider 5.4m
Length: 5m +
Engine: Yamaha 85 Origin
Join Date: Oct 2011
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Hi, it is quite surprising you can get this from your 75 four stroke. Normally SR 5.4 won't chine hop until about 37, 38 knots. My guess is you might be trimming the engine up a bit too much and rising the bow high. With the added weight of the 4 stroke might make a difference to trim. If you think you're not, then not sure about this. I have a 85 yamaha 2 stroke on a 5.4 and actually find it hard to chine hop until getting about 37 knots. A possibility is the build of the Deluxe version on the early models seamed to be lighter than rescue version. That might make a difference. Not sure which you have.
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Old 01 March 2013, 19:40   #4
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The Honda 75 is a heavy lump as well, that might contribute a bit.
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Old 01 March 2013, 20:02   #5
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Country: UK - England
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Quote:
Originally Posted by ribsta View Post
Hi, it is quite surprising you can get this from your 75 four stroke. Normally SR 5.4 won't chine hop until about 37, 38 knots. My guess is you might be trimming the engine up a bit too much and rising the bow high. With the added weight of the 4 stroke might make a difference to trim. If you think you're not, then not sure about this. I have a 85 yamaha 2 stroke on a 5.4 and actually find it hard to chine hop until getting about 37 knots. A possibility is the build of the Deluxe version on the early models seamed to be lighter than rescue version. That might make a difference. Not sure which you have.
I am unsure of model
I think it was trimmed correctly, the boat was level on plane but as soon as I nailed it I thought I was going to lose control a feeling i have never had on a boat before.
Do you think fins may give a little more stability.
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Old 01 March 2013, 21:19   #6
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Originally Posted by teamplonker View Post
Do you think fins may give a little more stability.
No.

Changing the weight distribution a bit might.
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Old 01 March 2013, 21:47   #7
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Country: USA
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Make: 7m Willard /Avon SR4
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I have a SR4 w/ a 50 2stroke Yamaha and put fins on the outboard once, which made it extremely unstable. With no fins she starts chine walking at 35+ if trimmed up too high with only one person in the boat.
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Old 02 March 2013, 02:28   #8
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We had modern 90 2stroke opti on 5.4


It flew, but only chine walked right at top end.

There's something amiss
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Old 02 March 2013, 02:37   #9
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I only had me and my son on the boat ,The boat is set up with a jockey console positioned centrally and a fuel tank directly behind the console . At low speed the boat sits level .
Will the boat feel more stable with more passengers ?
Would the console be better positioned further forward?
Am I trimming the boat wrongly ?
I was taught to trim the boat by getting up to speed throttle back to bring the bow
down and get the top of the outboard level, you should now be at optimum speed.
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Old 02 March 2013, 02:51   #10
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Trim it all the way in and then trim it out slowly until it starts to feel wobbly.

Things to look for, trim tab behind prob needs adjusting, the engine should be offset to the starboard on the transome, get some more weight upfront. Also check to make sure that your gear box is a righthand (clockwise) rotating.

It might be when it's right up on the planing pad you are not used to it. Can you get another member to drive it?

We are out today if you are in the south?
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