Driving straight...having problems

[OldRedSled]

I just got a Great 17 Alumaweld Sea-dory with a 97 85hp Yahama prop center console. The problem is that the boat lays to the left at top speed. At low and mid range speed the boat is centered and runs good, AT top speed the boat rides its left edge and the motor wants to pull hard to the right. I have centered the little fin about the prop with no luck.
The motor is mounted on a Hi-jacker plate.

I do have a honda 5hp mounted on there but i noticed that problem before i put that on there.

Is there any solution to this tilted left riding and severe pull to the right by the motor at top speed. Since the pervious oldredsled was a pump tiller and this is a prop w/ a center console im a bit lost. :whazzup: :whazzup: :whazzup:

ORS

[scrod]

The "little fin about the prop" should not be centered. It compensates for the prop spin. Clockwise rotation prop would put the fin towards your left shoulder looking at it. It may take some adjusting to find the right spot.

[Fishplay]

Sounds like motor trim to me. If you have power tilt and trim try triming the motor up a little once your on plane. This puts a downward presure on the transom and will lift the bow a little. If you don't have power tilt and trim you will have to repin the motor itself. Transfer the pin one hole in the direction that moves the shaft away from the transom. This will cause the boat to come on plane slower but should eliminate the bow plow that I believe is causing your problem.
Hope this helps.

[Uglygreen]

Check to make sure the 85 HPis centered on the transom and not tilted to the side. I know this sound obvious, but you mingth be susprised. Is the boat balanced from side to side at a stop. Check weight distribution. Is there anything on the bottom causing drag on the left side (old repair, loss of undercoating, big dent) if so, that might be the problem. Is it cable or hydraulic steering? If hydraulic check and make sure no air is in the lines, air compresses causing motor to turn towards line with more air in it, bleed hydraulic lines. Gyroscopic precession can be a problem in some boats if the motor is way to large for the hull size, but that doesn't soumd like the case here. Is skag bent? might check that.

Otherwise, only go on rivers that curve to the right.

UG.

[get hooked]

Scrod is right. That little fin compensates for the thrust from the prop. You'll have to play with it to get the best overall results. Chances are you will have some pull from time to time from currents and wind. Good luck!!

Your boat is a republican and there is nothing wrong with it. If it leaned to the :shocked: left :shocked: I would scrap it. :grin:

[ 09-16-2002, 08:24 PM: Message edited by: Keta ]

[boater]

i agree with scrod, try moving the direction of the "little fin" to one side or the other until the problem goes away, good luck.

[Thumper]

"Gyroscopic precession"

Ooh! Ooh! A marvelous new term! I can't wait to use it. Waidaminit! What does it mean Ultragreen??

[Plugcutter]

I'll agree with FISHPLAY, the motor trim will fix the problem. My Tracker Targa 1800 is cured of the same pull by an ever so slight tweek to the trim. Then it runs sweet.

[Uglygreen]

Any spinning object, including boat moters, bullets, childrens tops, etc. acts as a gyroscope.

Gyroscopic precession is the tendancy for any spinning object (gyroscope / motor / propeller) to turn 90 degreees opposite to the plane of rotation when accelerating or decelerating. For example: in a single engine airplane, when the throttle is advanced (eg. takeoff) gyroscopic precession wants to turn the propeller, motor, and the whole airplane to which it is attached, to the right as the engine RPMs increase. The pilot must hold left rudder to compensate for this during the takeoff run. This is the reason the props on a two engine airplane turn in opposite directions, the precession from one motor cancels out the gyroscopic precession from the other engine.

Boats are similar. As you accelerate a single engine boat the gyroscopic precession wants to turn the boat off course. This is one of the reasons for the little trim tab, and the reason in twin engine boats one engine should counter-rotate.

The larger the mass of the gyroscope the greater the precession is. This means that the bigger the engine to hull ratio the larger the problem can be. But it should only affect the boat when accelerating or decelerating, constant speeds are not affected. I wouldnt believe this would be a problem for Old Red Sled, with an 85 HP on a 18' sled. Hydroplanes (with 400+ HP on a lightweight hull) are greatly affected. Next time you see a hydroplane race notice that the boats line up on the start 45 degrees or so off the course of the first leg of the race. At the go signal the boats hit there throttles and gyroscopic precession turns the boats on course.

And this is the most times I have used the term "gyroscopic precession" in many years If not my whole life. Happy? <g>

UG

[ 09-16-2002, 09:27 PM: Message edited by: Uglygreen ]

[get hooked]

Boy..... You said a mouthful there UG......

[Thumper]

Yeah........I knew that.........

[OldRedSled]

thanks everyone for the advice ill jiggle that little fin thingy to compensate for the gyrosocpic-X-pee-al-a-docious effect. ACtually i have heard of that allready. The force is perpendicualr to the rotaion. thanks again all

[Point-of-Sale Clerk]

Gee, as I read this thread I feel smarter already :grin:

[wetaline]

I feel like i just relived college (the academic side)... Oh theres the bell - time to go.

[chummer]

Hey uglygreen, did'nt you play the part of the postman on cheers a few years back? :grin:

[Uglygreen]

Hey now.. Thumper asked... ask and you shall recieve, and I have better things to do than sit in a bar. I sit on Ifish. Ha Ha

UG