Small Jon Boat - "twitchy" at speed.

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Terry Keeley

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Oct 10, 2009
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Searched but couldn't find my answer.

Got a 10' aluminum Tracker Jon boat with a Johnson 5hp O/B. Runs great but at full speed occasionally there's a fairly violent "twitch" in the steering, it's like someone suddenly knocked the steering over or something. Been running small boats all my life and never experienced this. Thought I hit something first time it happened.

What's causing it? How to stop it?
 
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robert graham

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Re: Small Jon Boat - "twitchy" at speed.

You may have hit a swirl or current in the water that will do that to flat bottomed jon boats...My 18' jon boat does that now and then when I cross maybe the entrance to a creek or tidal flows, causing the current to move. V hulls don't do as much. Good Luck!
 
roscoe

roscoe

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Re: Small Jon Boat - "twitchy" at speed.

Doubt that there would be chine walk on a 10' j boat.

a jerk or clunk felt thru the motor?

Sounds to me like the motor clutch dog is kicking in and out.

Worn clutch dog will do this, until it is even more rounded, then it will do it very often, till something lets loose.

Replace the worn parts, or have them machined flat, in some cases you can just turn them around - depending on the motor.
 
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Terry Keeley

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Re: Small Jon Boat - "twitchy" at speed.

Thanks for the ideas guys but I'm sure it's none of the above. Big flat lake, no chine walk and the motor's in top shape. Feels like a violent bow steer or something, just wondering if it's common with flat bottom Jon boats.

Never felt that before...
 
zopperman

zopperman

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Re: Small Jon Boat - "twitchy" at speed.

How old is the motor? I'm with roscoe on this one... How often does it happen? For how long?
 
smokeonthewater

smokeonthewater

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Re: Small Jon Boat - "twitchy" at speed.

what condition is the bottom in? banged up with a nasty hook could be scary
 
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Terry Keeley

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Re: Small Jon Boat - "twitchy" at speed.

Boat's brand new with a good bottom, just got it at Bass Pro.

It's like someone jerked the O/B suddenly about 5*, quite violent. I did tighten up the tension on the steering and will try it again in the morning...
 
zopperman

zopperman

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Re: Small Jon Boat - "twitchy" at speed.

Is the motor tightly secured to the transom?
 
26aftcab454

26aftcab454

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Re: Small Jon Boat - "twitchy" at speed.

could it be that your on plane and the bow catches a small wave and it digs in?
My old aluminum 1957 LoneStar ElDorado (18FT) with a 115hp Evenrude would do this but at speed.
 
jacoboregon

jacoboregon

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Re: Small Jon Boat - "twitchy" at speed.

I agree with Roscoe, or it could be the prop hub is slipping.

Have you marked the hub to see if the marks stay aligned?
 
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Terry Keeley

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Re: Small Jon Boat - "twitchy" at speed.

Thanks again guys for the help, I'll check it out in the morning...
 
DuckHunterJon

DuckHunterJon

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Re: Small Jon Boat - "twitchy" at speed.

My flat bottom duck boat does something similar, though it feels more like a clunk than a jerk to one side. I've pretty much concluded (with out scientific proof) that it's the hull sucking air under when at speed. Feels wierd, but doesn't seem to do any damage.
 
lncoop

lncoop

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Re: Small Jon Boat - "twitchy" at speed.

DuckHunterJon said:
My flat bottom duck boat does something similar, though it feels more like a clunk than a jerk to one side. I've pretty much concluded (with out scientific proof) that it's the hull sucking air under when at speed. Feels wierd, but doesn't seem to do any damage.
Click to expand...

My money is on something like this. Spun hub and clutch dog seem unlikely unless the motor has seen some serious combat. John boat hulls can do some strange things under power, and the smaller they are the more pronounced said strange things can be.
 
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robert graham

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Re: Small Jon Boat - "twitchy" at speed.

DuckHunterJon said:
My flat bottom duck boat does something similar, though it feels more like a clunk than a jerk to one side. I've pretty much concluded (with out scientific proof) that it's the hull sucking air under when at speed. Feels wierd, but doesn't seem to do any damage.
Click to expand...
That's probably it, like an air bubble under the hull. My 18' jon gets a bit twitchy at speed sometimes....
 
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Terry Keeley

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Re: Small Jon Boat - "twitchy" at speed.

Had it out this morning and think I "fingered" it out. The bow is firmly planted at speed and the slightest movement of the O/B makes it bow steer abruptly, it's very darty. Gonna try to get some angle on the motor to loosen the front end up a bit and see if it helps.

Haven't had a Jon boat before and maybe the little 10' with a 5 horse is a bit too much...

Thanks for all the help! :)
 
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Tnriverluver

Petty Officer 3rd Class
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Nov 2, 2011
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Re: Small Jon Boat - "twitchy" at speed.

Your boat is only rated for 3hp max. Your are nearly double the rated max so that could be part of the problem.
 
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