Problem stabilizing at speed

E

Eurocat

New Member
Jun 25, 2013
6
NJ
Boat Info
1998 Sea Ray Sundancer 250
Engines
5.7 EFI w/ bravo III
Hello everyone.

Being somewhat new to boating (other than jet ski and small boats), i am having a problem keeping the boat
stable (straight attitude) at speed. It "rolls" mostly to the right, but has happened to the left as well. Basically it occasionally leans without an apparent reason. I tested the trim tabs while on the dock and they seem to be working, however, while underway, they don't seem to correct the problem. I usually have to cut speed, temporarily worsening the lean, and once slow enough it corrects itself.
I have tried to see if it was based on occupant position, but it seems to happen while no one has moved, thus no offset of balance has occurred.
I have read regarding the tabs and their function, operation mode (short bursts) and tried to follow it to the letter, but to no avail. Btw, the "leaning" is usually followed by a change of direction with out any input to the steering.

Has anyone else experienced anything similar? If so, do you know the cause?
I'm taking it out again on Saturday, and if you have any ideas at all it might be worth a try.
Maybe some "leaning" is normal and i'm just not used to it...

Thank you in advance for your help.
 
Seems like you are on the right track with monitoring your load distribution, keep in mind though its just not people that make up the weight. As far as tab operation, you are correct again with the "short burst", all I can add is that you MUST give the boat time to react. Hang on to it and let the boat react & settle before making a second adjustment. Remembering which way the buttons work is important too. Go over it in your mind thoroughly before starting out.

Next time out try the tabs fully retracted, don't touch them & note what happens. I can tell you two things, it takes some practice & some getting used to. And any lean is not normal. You should be able to get the boat to flatten out. Keep at it, you'll be glad you did.
 
I'm thinking you are at speed with the tabs fully down... backwards of what you should be. Is that possible?
 
hopefully it is not a worn gimble mount large amounts of play can cause steering changes

does your out drive have a torque adjustment tab on the lower foot your problem could be torque steer

hopefully its tabs as others have posted wanted to give you some other things to think about
 
+1 on the torque. I thought I would explain for the OP since he is somewhat new to boating. There is, should be, a small rudder type device under your cavitation plate (the plate above your prop) and aft of the prop. This little rudder is used to adjust subtle issues like torque steer. You will want to make sure its there in the first place. The reason I say this is because these are usually made out of zinc and used as additional anodes. It may very well be gone. There typically is one bolt to adjust and you would want to move it about one degree at a time and test.


Gary
 
Try bringing the tabs up a bit. If they are too far down they can hold the bow down too far and cause "bow steering" that can cause the boat to veer to one side or the other.

Tom McGow
Bennett Marine
 
Also make sure you are trimming the drive up at speed. Drive full down and you will also cause bow steering.
 
This sounds very similar to the handling of my 260DA. Here are a couple of thoughts:

Loading - remember that fluids count. If your holding tank and water tanks are on opposite sides of the boat like mine, you often start out with a full water tank on one side, and a less than full holding tank on the other. This will cause a list towards the water tank side. An empty water tank and a full holding tank will get you a list to the holding tank side. You can put more weight on the side with the empty tank, or you can fix it with the tabs after you get on plane.

Drive trim - you should be able to get the boat relatively stable by gradually raising up the drive while the boat gets up on plane (and a little more after it is up). There are 3 things to look for when trimming the outdrive: First is how the engine sounds. When you get it right, the engine will sound like it is running well, and not laboring (I can't describe the sound, but you will eventually understand - just keep listening). Second, the boat will almost level itself out when the drive is trimmed properly. Third, the bow will seem "balanced". By that I mean that if you go over a wave, the bow will not take off up into the air, or come crashing back down on the other side. If your bow is smashing down after you go over a wave, use a little more up drive trim. If you bow launches upwards, use a little less up drive trim.

Tabs - After your drive trim is set, use 1-2 second bursts on the top of the trim tab button on the bow high side, and then wait 4-5 seconds to see how the boat reacts. Once you get it level, you can stop trimming. The owners manual for my boat explicitly states that when running at cruising speeds, the tabs should be fully up unless the rear is heavily loaded. I have found that my boat runs nicer if I over correct the original list, and then use the opposite tab just enough to bring it back to running level again. This seems to help the bow stay more steady at the proper angle, and also seems to minimize the side to side list when there is movement on the deck. That just becomes a little less noticable and easier to correct. You just need to be careful not to end up running both tabs too far down, or you might end up with a boat that is a little harder to control due to bow steer. Remember which tab you started using, and make that one the primary tab that you make adjustments with. The second tab that you put down (a little) should stay put until you drop off of plane.

I hope this helps ya.
Michael
 
Thanks for the replies guys.
While i'm out tomorrow i'll do some further tests and try to narrow it down.
In the meantime, i came up with a couple of options. Could have been some wind influence as it was not a constant tilt. It would come on all of a sudden and every time did i was going over 15 knots. The fact that the bimini top was fully open could have acted like a sail thus tilting it in the direction of the wind. This is however speculation as i was not paying attention to it's particular direction, but in retrospect based on how the waves were hitting, it could have been part of it.
I have a bravo 3 so i would assume it cancels out any torque issues unless one of them would for some reason stop spinning. I am not familiar with they way it's engineered, but since when you spin them by hand they counter rotate, it implies they are on connecting gears thus making it impossible for them to operate independently.
Assuming torque issues are eliminated, still leaves a possible gimbal problem, wind, or some other unknown variant.
I still need to look into the tabs, but i know that when i left the dock, they were both in the full up (retracted position) thus the bow would have an up attitude. if one of them by any malfunction did drop, it would have induced the tilt. This is also an option i need to explore. Maybe Tabman might have an idea if something similar has ever happened.
I will leave the dock tomorrow with the tabs parallel to the waterline to test out some theories. I will close both biminies and keep track of wind direction to see if that is the way the tilt occurs. If nothing proves conclusive i will pull the boat out of the water to check for any gimbal malfunction. The marina did change the gimbal bearing before i took it out for the season, so i would hope they checked the other components, this is however wishful thinking.
Hopefully i can come back with something that might be useful to other members in the future if similar problems are encounter.

Any other thoughts or ideas based on this new info would be welcome.
 
Last edited:
Are you boating in an area with lots of traffic? It sounds like what happens when you are caught on a wake (or wave) parallel to your direction of travel.

Sent from my Nexus 7 using Tapatalk 2
 
Well, found one problem.
The tab actuators were wired backwards. right was actuating left. So as i tried to correct the tilt, i was just making it worst.
Didn't get a chance to test more because of heavy wind and thunderstorms on Saturday.
I tried to move the outdrive left to right by hand, and found there is a little bit of play. Maybe 1 or so of movement. is this normal or there shouldn't be any at all?

Ty
 
Eurocat said:
Well, found one problem.
The tab actuators were wired backwards. right was actuating left. So as i tried to correct the tilt, i was just making it worst.
Ty
Click to expand...

Whoops, they are wired that way by design. For example, if you want the port side of the boat to go down you need to engage the starboard tab.
 
mwph said:
Remembering which way the buttons work is important too. Go over it in your mind thoroughly before starting out.
Click to expand...

Euro - The tab buttons can be tricky if you don't get the operation straight in your mind before starting out. I've heard a bunch of different ways to keep it from being confusing. I like to think of the four corners of the boat in relation to the four corners of the switches. - Think it through & you'll get used to it.
 
i see so instead of trying to raise the starboard side i should be thinking of lowering the port side. (or something to that effect).
guess i have to rewire my brain rather than rewire the tabs. lol
 
Eurocat said:
i see so instead of trying to raise the starboard side i should be thinking of lowering the port side. (or something to that effect).
guess i have to rewire my brain rather than rewire the tabs. lol
Click to expand...

Look at it this way; The tab switches are normally labeled with bow down or bow up pictures. So if you want the port bow down, you push the port down switch, which lowers the starboard tab, raises the starboard stern, which in turn lowers the port bow.
 
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