Boat is falling over!

[dsiekman]

I have a 2000 Cobalt 293 with twin volvo 5.0's with DP's. the boat also has bennet trim tabs. Everything was great until about a couple weeks ago when I pulled the shifters and throttles out to lube and paint them. I went out soon after and the boat seemed to pull to one side, even though the engines were sync'd. Thought it was just the wind. Went out this morning, started with both tabs all the way up and both drives trimmed down. Dead flat and she ran fine. Coming back she started getting a little more squirrelly. I would punch the trim tab, she would right herself, then ten seconds later she'd heel hard over. A couple times I had to come down off plane because I was starting to lose control. Happened in both directions and sometimes when the boat had been running dead level for a couple minutes. What gives? It was almost like the tabs had a mind of their own. Maybe something didn't go back together quite right?

Any help is appreciated!

 

[Bob_VT]

Re: Boat is falling over!

Hydraulic tabs or electric? If the are hyd then you might have a leak....... if elect......might be the control unit

 

[dsiekman]

Re: Boat is falling over!

I believe they are electric. There is only one line (that I'm aware of) into each unit, and nothing in the engine compartment. Also, they are VERY quiet. I can only hear them move with the engines off, not like engine trim where you can hear the pumps even underway.

Do you think something didn't get hooked back up right, or do you think that is a just a coincidence?

 

[Bifflefan]

Re: Boat is falling over!

Hyd has only one hose going to the tabs, the are spring loaded to return to flat.
You said that when you ran them flat it did fine and then coming back it twitched out a bit. Did you have the tabs down then?
If so then id suspect the tabs leaking, if they were flat and it did it id look else where.

 

[dsiekman]

Re: Boat is falling over!

I started them out all the way in(I think - All the way to "Bow down"). I had two passengers and about 3/4 tank of fuel. The load was well balanced. I would bump them - just push the rocker switch once as if pushing a button, didn't hold it down. Then I would give it 30 seconds plus to adjust. It would seem to adjust, run flat, then another 30 seconds later fall over in the other direction...and I mean hard over. It actually scared me enough I considered making the run back home at idle.

She's a big girl, 29' and around 9000 lbs with fuel and water...plus about 750 lbs of people. I have heard people complain about the small tabs on this boat - about 9" x 12", but it has never done this to me and I've run in all kinds of conditions with a lot more and less weight, wind, etc.

 

[dsiekman]

Re: Boat is falling over! - UPDATE

Re: Boat is falling over! - UPDATE

Okay, so we beached the boat on a sandbar today so I could take a closer look. I had my wife operate the tabs while I got in the water. The pump would run and limit out, but no movement. I couldn't even move them by hand. I checked the reservoir and only had about an inch in the bottom. Guessing that is not enough. Also noticed my drive oil on the port engine was low. $#*% Volvo doesn't have a low drive oil alarm...or maybe it was removed along with my engine alarms. Former owner or his mechanic must have been real bright.

So, is low fluid my issue? Obviously it went somewhere. No oil in the bilge, so I am assuming I lost it to the water. That being said, the fluid in both the tab reservoir and outdrive reservoir was clean and showed no signs of water intrusion.

Also, my wife reminded me that something similar had happened BEFORE I started screwing around with the shifters and wiring for the trim. It just seems to be getting progressively worse.

Thoughts?

 

[Bifflefan]

Re: Boat is falling over!

Well first you need to get the tab reservoir full and cycle them a few times to get the air out. Then they sould move. Look for leaks after they are full of fluid.

As for being able to move them, I weight about 170 and have to lean on them a fair bit to get mine to move. Its a hefty spring in there.

I think your issue is the tabs are failing you.

 

[dsiekman]

Re: Boat is falling over!

Thanks, I'll try that. I'm a few beers heavier than you, but the boat was in the water and didn't/couldn't put too much into it. Unfortunately I don't have a trailer for her so looking for leaks could be a challenge. The bilge is spotless, so I don't think it is leaking inside. Seal in the ram maybe?

 

[Tabman]

Re: Boat is falling over!

dsiekman,

I just posted this at The Hull Truth, where you asked the same questions,

I doubt the "rolling" issue you describe is being caused by the Trim Tabs. When fully retracted, as they are now, the Trim Tabs should angle slightly up from the bottom of the hull. That way they have little or no contact with the waterflow and should not affect the boat's running attitude.

I think you may have the bow trimmed a little too far down with the outdrives, great for speed, but if the bow cuts into a wave a little too deeply it can cause what is called "bow steering" and pull hard to one side or the other with the boat rolling in the process. Some hull shapes are more prone to this phenomena than others. Try trimming the drives out a bit at a time during your next outing and see if that solves the problem.

Ok, on to the Trim Tabs;

It is unusual to loose that much fluid in the system. As you suspect there may be a leak in one of the actuators (rams). You can run the boat without the Trim Tabs for the rest of the season if a haul out is out of the question.

Were the Trim Tabs working prior to the last outing or were they working before that?

We can try filling the reservoir wit Automatic Transmission Fluid (ATF) and then run the Trim Tabs up and down 3- 4 times to automatically bleed the air from the system.

Use any type of Automatic Transmission Fluid (ATF). Don't worry about the exact brand or type - it will all work, and can even be mixed. To add fluid, remove the Lexan cover on the HPU, locate the "filler stack" in the left front corner of the reservoir. There is a round plug sealing the filler stack. Remove the plug and add fluid to the full line on the reservoir. Note: Add fluid only with the trim tabs fully retracted (up). If your reservoir does not have a full line, add fluid so the fluid level is about 1 inch below the top of the reservoir with the trim tabs fully retracted (up).

If they work then put both Trim Tabs in the full down position overnight. The Trim Tabs will retract by themselves if there is a leak in them.

If there is a leak in one or both, it is usually a very easy fix with the boat out of the water, the O-rings can be replaced in them. It's an easy DIY job for the average boat owner and takes about 15 minutes. If you need to replace the O-rings we can arrange to have them mailed to you at no charge.

I hope this helps. Let me know if you have any other questions.

Tom
Bennett Marine

 

[Bifflefan]

Re: Boat is falling over!

The bilge is spotless, so I don't think it is leaking inside. Seal in the ram maybe?

I would say yes. But it may be very small and hard to find. get them full and working again and go from there. Watch the fluid close for a few trips and see.

 

[dsiekman]

Re: Boat is falling over!

Thanks, all! That's some great customer service! I really wasn't expecting an answer out of the manufacturer on a Sunday evening! Also just found the Hull Truth tonight and didn't realize the two were related. Sorry for the multiple posts. Anyway, thanks for the input.

Tabman - should I respond to you here or both places? I had not had the issue before, and yes, the tabs seemed to work previously. The boat would definitely react to the adjustment.

This felt like more than bow steer. The boat was laid over as if turning sharply. When it got bad I was actually trimmed out a little.

 

[Tabman]

Re: Boat is falling over!

You can reply where ever you like, I watch both forums.

Let's try refilling the pump and going from there, if that is OK with you.

Tom
Bennett Marine

 

[dsiekman]

Re: Boat is falling over!

Is it possible that the contacts in the rocker switches were sticking causing the system to continue to trim? Or, with the low fluid level, is it possible that it was just reacting slowly? Another thought - if no pressure causes the rams to return to the "up" position, is it possible that one of the tabs was catching a cross current and being pulled down thereby causing drag and pull? Kind of like sticking your hand out the car window and turning it slightly?

 

[dsiekman]

Re: Boat is falling over!

Will do. I'll keep you posted.

 

[Tabman]

Re: Boat is falling over!

dsiekman,

I'm standing by to see what you find.

The other scenarios you posted are quite unlikely, as the low fluid would not allow the Tabs to move enough to do much, and the water flow under the Trim Planes would not cause them to be pulled down unless they were badly cupped (bent).

Tom
Bennett Marine

 

[dsiekman]

Re: Boat is falling over!

I'm hoping to get down to the boat tonight to fill up the reservoir. One thing I did notice when I pulled the lexan cover off was that the plug/cap was actually up about 1/4" and loose, not pushed in as I assume it should have been. Could this have allowed additional air into the system? Also, the tabs had been repsonding previously. If they were right at the line of having just enough fluid to operate, could a good hit crossing a wake have forced one to loose pressure and retract...maybe if there was air in the lines? I don't fully understand all of the specifics of how the system operates, just trying to analyze what would have caused it to respond as it did...I'm an architect, I can't help myself. I usually run the boat very conservatively, though I have been out when it was rough. The day we test drove it there was a small craft advisory on the bay. No problems. Typical weekend boat traffic around Annapolis. No problems. This has been a very recent change in handling, so I have to believe something has changed. The actual tabs appeared to be fine outside of some barnacles that need to find a new home.

Thanks again for all your help!

 

[Tabman]

Re: Boat is falling over!

The filler cap is meant to be a bit loose, i.e. not a snug fit. The system forces the air out of the lines every time it operates.

Simply put if there is enough fluid in the system to lower a Trim Tab it will be locked in place by the valve on the pump, and there will be no air in the line. Since you cannot compress a fluid the Trim Tab cannot move with without a leak of some-sort in the system.

That is why we are going to leave them fully down overnight if they work when you fill the pump. If there is a leak, the actuators will retract (there are big return springs in them) and we will then know what to fix.

Tom
Bennett Marine

 

[dsiekman]

Re: Boat is falling over!

Got it. Thanks!

 

[dsiekman]

Re: Boat is falling over!

Okay, so I topped off the reservoir tonight and ran the tabs up and down a half dozen times. They move! However, they only move about 4-5" at the tip. I wasn't about to climb in the water at the marina, so I was judging with my boat hook. Is that normal travel? Also, when the tabs were coming back up they made a fairly unpleasant gurgling sound, kind of like blowing bubbles in milk, for about the first 4-5 seconds. Air? It seemed to take about 12 seconds for them to go all the way down. I left them there and will check again tomorrow night.

I had to unscrew one of the solenoids to get the funnel in the right spot. Not sure if that matters, but in the interest of full disclosure...

 

[Tabman]

Re: Boat is falling over!

That's great news!

Yes the movement seems about right. The actuators (rams) move about 2-1/2" and that translates to about 4" at the end of the Trim Plane. Both Tabs moving together take about 10 -12 seconds to go from full up to full down and the gurgling sound is indeed the air being purged from the system.

So far so good!

Let's see if they are both down tomorrow.

Tom
Bennett Marine