Boat Oscillates Right and Left On It's Own

TyeeMan

Master Chief Petty Officer
Joined
Feb 27, 2006
Messages
849
Hey Everybody,

I asked this question about 10 years ago and don't remember the answer, , or maybe something changed since then.

So my boat is a Lund Tyee 1950 IO/Alpha One Gen 2 drive. When in forward gear at idle the if I don't counter steer the boat will basically turn right and left all on it's own and eventually would totally go off course.

10 Years ago I had a 1750 Tyee with an Alpha one which did the same thing.

My boat prior to my current boat was a Tyee 1850 but with a Volvo Duo Prop. That thing went straight as an arrow at idle and wouldn't deviate from course at all. My guess is because of the counter rotating props.

The question is - is there an adjustment or something that would help keep the boat going in a straight line at idle or is this an anomaly common to IO's. Never had this problem with boats with outboards. What gives?

Thanks!
 

H20Rat

Vice Admiral
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Mar 8, 2009
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5,199
Go faster... Your dual props mostly masks the problem, but it is more a factor of the hull design than anything else. Most planing v-hulls do that, some are much worse than others. They are all highly speed dependent and will all have a speed where they wander all over the place.

(and it isn't just IO's... I've had twin jet powered boats do it as well as outboards. Shorter and wider tend to wander more. I haven't experienced an inboard do it, but certainly not impossible.)
 

alldodge

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Mar 8, 2009
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Single engine V-hull will do it at idle speed, cannot stop it. My B3 drive does the same thing and it drafts 42 inches to the bottom of the skeg

Tyee 1850 but with a Volvo Duo Prop

I would like to see that. Only Tyee I know of is made by Lund and their outboards.
 

jkust

Rear Admiral
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Aug 2, 2008
Messages
4,942
Slow speed wander or bow wander or other names for it. It is bog standard for single engine i/o's. Some seem to zig zag and go ultimately on a straight course and some seem to wander one way further than the other pushing you off course.
 

jimmbo

Supreme Mariner
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May 24, 2004
Messages
12,944
If you can find a boat that is offered in an Outboard version and in a Stern Drive version, the Outboard version will usually track pretty straight, while the I/O version will wander back and forth, almost like a Dutch Roll in a plane. It might have something to due with the I/Os heavier weight at the stern, and the resulting angle of the hull to the water at low speed.
 

jimmbo

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May 24, 2004
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Single engine V-hull will do it at idle speed, cannot stop it. My B3 drive does the same thing and it drafts 42 inches to the bottom of the skeg



I would like to see that. Only Tyee I know of is made by Lund and their outboards.

Lund offered some boats with I/Os. I hauled a few to a boat show a few yrs ago
 

TyeeMan

Master Chief Petty Officer
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Feb 27, 2006
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849
Thanks everybody. Kind of what I thought, just have to live with it.

Yeah my Tyee with the duo prop was a conversation piece to be sure. It 1995 so it had the "old school" DP2 where the exhaust exited through the antiventilation plate. Kinda had a nice exhaust note ( for 4.3L) when the plate came out of the water.

I love my Mercruiser but boy I miss the sweet shifting of the Volvo drive and the performance of the duo prop.
 

wire2

Lieutenant Commander
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Jun 25, 2007
Messages
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No, you don't have to live with it. A pair of spring loaded trim tabs will completely eliminate it. I can idle through 1,000 ft of narrow channel without touching the steering wheel. (19' Glastron). They also cut down the "wheelie" during acceleration from idle.I have the Nauticus Smart tabs, all plastic, even the bolts. ~ $130 but other brands will work also.
 

TyeeMan

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Feb 27, 2006
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Hmm, very interesting. I'll take that into consideration. Thanks for the heads up.
 

HT32BSX115

Supreme Mariner
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Dec 8, 2005
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10,083
No, you don't have to live with it. A pair of spring loaded trim tabs will completely eliminate it. I can idle through 1,000 ft of narrow channel without touching the steering wheel. (19' Glastron). They also cut down the "wheelie" during acceleration from idle.I have the Nauticus Smart tabs, all plastic, even the bolts. ~ $130 but other brands will work also.

They always make that claim. Tabs will not eliminate it on all boats especially deep "V" boats. My Fourwinns Liberator has Bennett Tabs on the back and a Bravo III.

It wandered with the originally installed King Cobra and it does it with the Bravo III regardless of tab position. Boats wander because of the center of motive force is at the back, and at slow speeds there is little or no keel to keep it going straight. So the a slight turn is actually the boat going sideways (being pushed from the back)

No amount of additional drag on the back (tabs hanging down, dragging double anchors etc) will prevent it.

Spring loaded tabs will also add drag that will will not only reduce top speed but will also increase fuel consumption at any planing speed. (additional drag always = additional fuel consumption)

If you want to prevent "wheelies", You're right.....Tabs can help here if you run them full down for holeshot. (can't do that with spring-loaded tabs though)

Without tabs (or with the tabs full-up), you can start out with the drive trimmed initially down (IN) , and trim up as you begin to plane. The Bravo drives have IN-limit blocks that can be removed if the drive will not trim in far enough. I removed them on mine. Not sure if the Alpha has a provision for IN-limit blocks.

The only time I run my tabs full down is when I pull a wake-board skier. It allows me to go very slowly, keep the bow down enough to see easily over it, prevent the boat from accelerating onto a "Plane"
 

wire2

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Jun 25, 2007
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Ok, I'll readily accept that they won't cure all boats. I'm only going by personal experience, and that of several friends, all with similar size and power.
They worked very well on;

84 Glastron 190SX 5.7
10 Sea Swirl 20 ft 5.0 mpi
06 Sea Ray 21 ft 5.0 carb

As for substantial drag & top speed reduction, I'm not convinced. At planing speeds, (25 mph and up) looking over the stern, they're pretty much pushed up parallel to the bottom of the boat. The water flowing on the tab surface area seems to easily overcome the springs at speed..
 

Paddichuck

Cadet
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Sep 5, 2012
Messages
26
I believe the wander is caused by the turbulence created behind the square transom - creating low pressure pockets that'll pull the boat one way or the other. As stated above, there is not enough stabilizing force from keel (and no rudder) to counteract the dynamic forces at that speed.

The tabs may in fact act as stabilizers to some degree, making the boat less apt to swing with slight pressure imbalances from the turbulence, but the force necessary to push those tabs up at speed comes from the engine and does detract from available propulsive force. It may be negligible but it will add some drag.

Our 21' Starcraft deep V i/o wanders all over the damned place at low idle. It adds to the boat's charm. It straightens out with a bit of throttle.
 

wire2

Lieutenant Commander
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Jun 25, 2007
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I have an additional possible cause. A planing hull is designed to operate with the bow out of the water. At idle, the bow's curved surface is pushing into the water. I believe there may be a tendency for it to steer the bow left and/or right, until compensated at the helm (or by a pair of tabs on most boats)
 

JASinIL2006

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Feb 10, 2012
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I have SmartTabs and while I really, really like what they do for my boat, they do not eliminate wander much at low speeds. They're great for keeping the nose down at holeshot and they completely eliminated chine walking at high speeds, but they don't do much for bow wander. On my boat, anyway.
 
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