Mercruiser 3.0 Alpha one Pulling hard left

[Kasdanh]

I have a 1996 Bayliner Capri 1750 bowrider that is pulling hard left on takeoff. The problem is so bad that the boat cannot be driven by anyone that is not strong enough to overpower the left turning action. At cruise it pulls left but just slightly. The main problem is when first accelerated it pulls very hard left (especially when from a complete stop ie. pulling a skier). The trim tab has already been adjusted accordingly and I tried trimming out the motor as well to no avail. The only thing I can think it may be is the steering cable but I'm new to boats so not sure if that could cause a hard pull. Any help would be much appreciated.

 

[danond]

Re: Mercruiser 3.0 Alpha one Pulling hard left

If you burp the throttle with the boat on muffs does it want to turn, or does it happen in water only?

 

[Kasdanh]

Re: Mercruiser 3.0 Alpha one Pulling hard left

I haven't tried that yet. Should I do it in neutral or in gear? If it does turn then what could that be. I'll try it out today.

 

[danond]

Re: Mercruiser 3.0 Alpha one Pulling hard left

Either way. It should facilitate finding the cause vs. being in the water turning in circles!

 

[MikDee]

Re: Mercruiser 3.0 Alpha one Pulling hard left

Make sure you're turning the small trim tab on the drive the in the right direction. Have you read this: http://forums.iboats.com/showthread.php?t=250928

 

[Kasdanh]

Re: Mercruiser 3.0 Alpha one Pulling hard left

Thanks for all the help so far. I have read that article as well as many others regarding the trim tab and have had no luck. I tried both ways as everybody has a contradicting way of positioning the tab (including the mercruiser manual). So if I run the engine with the muffs and it turns what could the cause be? Also, do you think it could be the steering cable? Would a no feedback steering system help? Thanks again.

 

[Kasdanh]

Re: Mercruiser 3.0 Alpha one Pulling hard left

If I am behind the boat looking down on the stern should the trailing/back edge of the trim tab be right or left to push the boat right? Just wondering what you guys think.

 

[tig1142]

Re: Mercruiser 3.0 Alpha one Pulling hard left

the back of the trim tab should point in the same direction the boat is pulling. So if the boat is turning left, increase the tab deflection to the left. This will make the outdrive want to go to the right.

 

[MikDee]

Re: Mercruiser 3.0 Alpha one Pulling hard left

Trailing edge of the trim tab to the left:
Now, listen close, as the flowing water under the hull hits the tab, (building up pressure with speed), like a small rudder, it will push the back of the outdrive to the right, causing your boat to turn slightly to the right.

Trailing edge to the right:
It will move the back of the outdrive to the left, causing your boat to turn slightly left. Or it will try to overcome normal Clockwise rotation prop torque.

Clockwise rotation (as in most boats) Prop torque normally will cause your boat to pull to the right, because the prop is scooping water on it's right side, as it screws through the water creating forward thrust, this causes the outdrive to be pulled to the right, hence the boat pulling to the right

Counterclockwise (reverse rotation) props will do the exact opposite, and pull to the left.

You have 2 forces at work here, the trim tab torque, and the prop torque, the stronger one will win out at times.

You see, I not only told you which way to turn the tab, but Why!

 

[Kasdanh]

Re: Mercruiser 3.0 Alpha one Pulling hard left

indeed you did! Thank you so much. Since the major problem is when accelerating from a stopped position before it planes out do you think that the trim tab would have enough effect at those speeds to cause it to turn so hard? We tested it yesterday and I had my wife try to drive it and when she hit the throttle the boat did a full 180 and she couldn't fight it off. Could that be trim or you think it's another problem at work? Thanks!

 

[Rocky_Road]

Re: Mercruiser 3.0 Alpha one Pulling hard left

What prop, and pitch, are you running?

 

[Kasdanh]

Re: Mercruiser 3.0 Alpha one Pulling hard left

Not sure what the prop size is on there as it's kind of rubbed off the prop. I actually took it out to the lake the lake on wednesday and played around with the trim tab a bit more. I finally got it figured out and it was the trim tab. It seems as though it is just VERY sensitive to even slight adjustments. Thanks again for all your help. I appreciate it!