Trim Tabs-gctid382425

[Guest]

Could someone please explain the proper use of trim tabs. If I want to lower the bow of the boat can't I just use the tilt on the outdrive?

Thank you

1998 2355

[Guest]

simply put that only works while throttling up you need trim tabs for slower speeds

[Guest]

Lower the tabs to lower the bow. Raise the tabs and the bow will come up. Both of these situations are when you are under power. You also use the tabs to level your boat (side to side) to account for people moving around or uneven weight distribution. Think about trimming your outdrive. When you trim it up it pushes down which in turn will lift the bow.

[Guest]

Trim tabs can help getting on plane faster when you've got some extra weight on board, or keep the nose down when running in rough water, and/or leveling out the "lean" of the boat to port or starboard caused by winds, currents, or weight not evenly distributed. When you don't need them keep them full up when under way.

Use your outdrive trim to maximize your speed and economy when on plane. If you don't know the "sweet spot" for your configuration you can experiment with outdrive trim. Generally speaking you would trim "out" the drive until you get the maximum speed at a set engine RPM. Lots of rules of thumb regarding cruising RPM but again generally if you cruise at around 3/4 WOT RPM you'll be close to your sweet spot. So if your WOT is 4500 try cruising at 3200-3400 RPM. Then trim your outdrive out and see if speed increases(use GPS for more accurate speed measure rather than speedometer). If speed increases, keep triming out until speed drops then trim back in and you've found your sweet spot. Obviously there are electronic fuel flow devices that can make this a science, but for old school guys like me who haven't yet gone 100% digital, this work reasonably well.

[Guest]

Generally when your on plane, if you "trim" your motor you only way will be up or at least it should be and thats only going to rise the bow.

You wont need tabs much for keeping the bow down on that boat, 2355 does a good job on its own. I never used them for that, but I had to use them alot for leveling it out.

On my 3055 the tabs are used for getting onto plane, and keeping the bow down at cruising speed. At WOT I dont need them much my bow seddles down nicely, but at cruise she likes to be bow high so I use the tabs to counter that.

[Guest]

My preference is to keep trim at a point where the driveshaft and ujoints are as straight as they can be (minimizing wear), and this is usually with the drive almost all the way down.

For a good guide, I recommend reading straight from the source:

http://www.bennetttrimtabs.com/guidetotrimtabs.php

If anything, trim tabs lift and lower the back of the boat (which affects the bow). If you don't know how the trim tabs work, the actual buttons for them can be confusing because it can seem like it's backwards. I use them to help get up on plane, level the boat at a comfortable riding stance (which varies depending on weather/waves/cargo/people), and to level side-to-side. Also note that the larger the trim tab, the larger and quicker of an effect they will have.

I will also toss in this disclaimer: If you aren't sure how "responsive" yours are, only operate them in short 1-second bursts until you get an idea. If the boat ends up being VERY responsive to them, it can get very uncomfortable/dangerous quickly (and the higher up you are such as on a fly bridge, the worse it is) and cause the boat to lean hard and turn.

[Tabman]

If you are new to using Trim Tabs you may find this helpful in learning how to use them to achieve the best results. All boats react differently to Trim Tabs and the best way to find out what works best for yours is to experiment, and remember, use short bursts of the controls and let the boat settle down between corrections. Using them will soon become second nature.

Tom McGow

Bennett Marine

Getting and Staying Trimmed

All boats assume different fore to aft attitudes at different throttle settings and vary in sensitivity to lateral weight distribution.

A boat's optimum running attitude is determined by the operator. While some people may define optimum running attitude as the highest possible speed for a given amount of engine RPMs, others desire the best possible fuel economy, yet others may be trimming the boat to get just the right mix of speed and wake (such as for waterskiing.)

Optimum running attitude is when the boat is running to the operator's satisfaction for the given operating conditions. There are as many optimum running attitudes as there are boats and boat owners

A good way to determine a boats optimum running angle is to run the boat lightly loaded at full speed in calm water. During this test observe the boat's bow in relation to the horizon. Most boats run at or near their optimum attitude under these conditions. This should give you a feel for the appearance of the wake and bow spray when running at an efficient attitude. Note that not all boats will achieve their optimum running attitude under these conditions. Some boats will benefit from extra lift even when running at their maximum throttle settings. If you feel the boat will benefit from added bow down trim when running at speed start with the trim tabs fully up and deflect the trim tabs in short bursts. Be alert to changes in the boats handling, as you bring the bow down. Observe any changes in RPMs and/or speed. Adjust power trim if applicable.

Indications of Running Untrimmed

When a boat is running untrimmed the bow spray will exit the sides of the boat far aft. The stern wave (wake) is high and curling like a breaker on the beach. The rooster tail is high and close to the stern. The engine is laboring and the ride tends to be less smooth.

Indications of Running Trimmed

The bow spray moves forward and is flung not as far from the boat. The wake diminishes in height, as the rooster tail flattens out and moves away from the boat. The engine is operating under less load as evidenced by the tachometer and speed as well as sounding "less strained".

One Step at a Time

The key to obtaining optimal results from trim tabs is to operate them in short "bursts" and let the boat react before making another adjustment. The amount of time between corrections is influenced by the size of the trim tabs and the boat's speed. This will help avoid overtrimming or ending up with one tab too far down when correcting lateral trim. You will quickly become acquainted with a boat's particular traits.

Take Off

Properly sized trim tabs can significantly reduce the time needed to get up on plane. They also allow a boat to keep its bow down and stay on plane at lower speeds.

As the throttle is advanced the stern of the boat begins to squat, lifting the bow. As the boat accelerates, push the bow down position of the helm control in short bursts. The boat reacts by the stern lifting, the bow coming down, speed increasing, and reduced engine laboring. If you over do it and deflect the tabs too far the boat will end up overtrimmed. When over trimmed, the steering becomes "over sensitive" and wants to pull off course to port or starboard. If this occurs, operate the control "bow up" until the desired attitude is established.

Getting the Most from Power Trim

Adjust the trim tabs to achieve the desired running attitude. Then use the power trim to position the propeller thrust parallel to the water flow. If necessary, re-adjust the trim tabs to fine tune the attitude. By observing the boat's speed and engine RPMs the best combination of trim tabs and power trim will be apparent. Trim tab angle indicators and a power trim angle indicator are particularly useful in duplicating effective settings.

Trimming to Sea Conditions

When running into a head sea you want to trim the bow down so the sharp forward sections of the boat do their work cleaving the waves. This provides the most comfortable ride and minimizes stress on the boat (and passengers). In a following sea the tabs should be fully retracted for maximum steering response.

Correction of a List

The normal control setup for trim tabs operates in relation to the desired changes in trim and not the actual movement of the tabs. Therefore, do not think about what the tabs are doing, but rather on the control and what you want the boat to do. As above, make the corrections in bursts and allow the boat to settle to the new settings. You may find it easier to correct the boat's fore and aft attitude before you correct the side to side trim.

Correction of Porpoising

Operate the tabs in very short bursts of about half a second. Continue until porpoising subsides. The objective is to have only a very slight amount of tab deflection, just the amount needed to cure the up and down motion of the bow.

[Guest]

That's excellent!

Thanks TabMan.........

Sarah

PS - My new drop fins seem to really help - Thank you!

[Tabman]

LazyCrusr wrote:
That's excellent!

Thanks TabMan.........

Sarah

PS - My new drop fins seem to really help - Thank you!

Sarah,

Thanks! I am delighted to hear that the drop fins help! I hope you have a great season.

Tom

Bennett Marine

[Guest]

If I want to lower the bow of the boat can't I just use the tilt on the outdrive?

No. The outdrive should be tilted for maximum efficiency, then the tabs used to control attitude. The outdrive is not for attitude control.

[RinnyBeth]

we fixed our trim tabs when in drydock.. when we are going up on step, the bow is up in the air and I cant see anything but skies and clouds.. lol.. we kick in the tabs and it lowers the bow and then I dont need a bloody booster seat to steer..:worth... we kick in the tabs when we hit over 15 knots and make a killer rooster tail off the back you can surf on...





15 knots

[Guest]

The Tabman Rocks

I made up a little cheat sheet with highlights of his detailed explanation found earlier in this thread.

I used it on the weekend and found it extremely helpful for a quick adjustment here & there. Had my clunky beauty screamin' around the pond and totally rippin' up the water!

I'd surely suggest to anyone who has not yet mastered the trim tab/drive trim duo of adjustments to read his instructions carefully and put 'em into practice!

Tabman,,,,,you're the best!

Capt Sarah and her REALLY FAST boat

[Tabman]

Tom

Bennett Marine

[2850Bounty]

We recently saw the new movie "The Avengers"!

I was rather dissappointed to see that Tab Man was not cast among the other Super Heros!



As usual, Tom is right here with the answers! :coo-

.

[Tabman]

2850Bounty wrote:
We recently saw the new movie "The Avengers"!

I was rather dissappointed to see that Tab Man was not cast among the other Super Heros!



As usual, Tom is right here with the answers! :coo-

.

Okay, now I'm blushing!

Thanks guys!

Tom

Bennett Marine