I have a 1987 overnighter, I love the boat. I had to get it repowered last year and I put a yamaha 150 4 stroke on it. The boat goes along nice. Heres the dumb part. I had all the controls and steering cable replaced. now the boat is VERY hard to turn left. what can I do?
Stupid question
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Doc Stressor
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Idle and low speed its ok. High speed it takes a lot of muscle. Could it just be the tork of the 4 stroke?
I guess taking it back to who ever did the install is out of the question? Sounds like one of the cables might be kinked. Hydraulic system is probably better, will cost at least a grand just for the kit, they are fairly easy to install
Doc Stressor
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Then the problem is either your torque trim tab adjustment or the engine trim angle.
If the boat wants to steer to the right (hard to steer toward the left), adjust the zinc anode fin located behind the propeller so that the REAR of the fin is angled to the left when looking down from the top of the anti-ventilation plate. This will deflect the stream of water from the propeller to the left, which will push the rear end of the boat to the right and minimize the steering effort toward the left.
You carry out this adjustment in increments. It is a matter of trial and error. Just keep moving the rear of the tab to the left until the propeller torque pull is neutral when the boat is trimmed properly and on plane.
It is normal for a single engine boat to pull toward the right until it gets up on plane. The further in the motor is trimmed, the greater the pull. Once the boat is on plane, you should be able to trim the engine out until the steering torque is neutral. You can do this only when the torque tab is adjusted properly.
The Overnighter hull does not respond well to engine trim. That is, the running angle doesn't change much until the propeller almost starts to blow out. It can pull hard unless you get it set up right.
Close but no cigar.
Contrary to what you would think, the trim tab under the cavitation plate does not redirect thrust, instead it adds drag in a certain direction. Therefore, if the vessel is hard to steer left, you move the rear edge of the tab to the right. That adds drag towards starboard and makes the vessel steer towards port. Yup, it sounds crazy but that's the way it works. Small adjustments make a lot of difference. I find that rotating the tab about 15 degrees or so is a good place to start. In addition, the optimal tab setting is speed dependent, do if you tune it for WOT, it wont work as well at lower speeds. Remember to mark the tabs position before removing it for replacement so that you can get the new one set up correctly the first time.
Contrary to what you would think, the trim tab under the cavitation plate does not redirect thrust, instead it adds drag in a certain direction. Therefore, if the vessel is hard to steer left, you move the rear edge of the tab to the right. That adds drag towards starboard and makes the vessel steer towards port. Yup, it sounds crazy but that's the way it works. Small adjustments make a lot of difference. I find that rotating the tab about 15 degrees or so is a good place to start. In addition, the optimal tab setting is speed dependent, do if you tune it for WOT, it wont work as well at lower speeds. Remember to mark the tabs position before removing it for replacement so that you can get the new one set up correctly the first time.
Doc Stressor
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:sorry Yep, seasick is correct. I've been fishing 2 days in a row and had a brain fart. The principle is similar to lift on an airplane wing. The rear of the torque tab needs to move to the right to correct for a pull to the right.
Since you said that you replaced the steering cable, I assume you are talking about a normal push pull teleflex cable. I notice on my 17 Mako that has a teleflext steering cable when the motor is trimmed in/down all the way, there is a lot of torque on the helm....when I tilt the engine up a little, the torque lessens. It still turns real easy to the right because that is the direction that the prop spins and you are pulling in the cable...when you turn to the left (port), you are pushing the cable out against the torque of the prop.....
As I mentioned, the trim tab adjustment is not a cure all for prop steer. Pick a speed range and a motor trim angle and adjust the tab for those settings. You should be able to get an acceptable setting.cgmiller said:
If the force needed to turn one direction increases as the vessel speeds up, it is most likely an incorrectly adjusted trim tab.
Many Yamis have index marks on the underside of the cav plate to use as a reference for setting trim tab angle. Looking from the underside, try about 1 1/2 tick marks clockwise ( about 1:15 in clock time) as an initial setting.