Trim Tabs

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New member
Nov 18, 2006
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Huntington Beach, CA
I have a 2520 Sport Cabin DV with bracket mounted 225hp. four stroke Yamahas. The original trim tabs are far to small. Can I install instead of the original 12" X 12" tabs 9" X 24" and improve performance? Will the added size effect my engines and props because of the change in water flow around the tabs???

Welcome to ClassicParker :D !

I can tell you firsthand that 9" chord (depth off the hull) x 24" span (width across the hull) versus the 12"x12" OEM tabs are a SIGNIFICANT upgrade. You'll be able to get on plane faster, plane at lower speeds, drop the nose without losing you miles-per-gallon as much as you would by deploying the far too small 12x12 planes, and overall imrove your response of the hull and it's performance.

The larger planes do not interfere with the water flow to the single motor one iota. In fact, I almost wish I had gone even wider, as trim tabs function by pushing down in the waterflow, which causes lift and drag. But wider tabs have a much higher ratio of lift to drag, whereas smaller tabs cause much more drag as a result of achieving the same relative lift.

In regards to twin OBs, you need 8" minimum from the centerline of the Ob to the inboard edge of the tab. See:

FWIW I have tested side-by-side 2 pretty much identical boats. Both wore 225hp OBs, one with Lenco 12x12s and mine with Bennett 9x24s. Both boats were equipped with fuel computers. Now our measurements were far from scientific, both of us ran ran both boats and we found the larger surface area tabs actually increased MPG when there was a small surface chop. The Lencos never increased MPG. When seriously deploying the tabs, we found as a 'guesstimate' that the 12x12s cost 20 to 40% in additional decreased MPG versus the 9x24s.

I assume thsse are Lenco brand tabs you have installed? I am guessing you do, so I'll let you in on a little info.

I have a "test project" underway with a reputable marine company to upgrade the existing Parker OEM tab system using 12x12s planes to those of equivalent surface area of the 9x24s. This would use the stock system and actuator, and only requires replacing the tab hinge and plane, which is of a new design. Replacing the existing hinge only requires a few 'new' holes to be drilled into the hull (to increase the span) as the new hinge uses the other bolt pattern already drilled into the hull.

Would it be equivalent to the upgrade of Bennett 9x24 planes? Probably not, but for a 1/4tr or so the price of the full price 'convert to hydraulics' upgrade, it should improve the performance of the Parker hull immensely! Stay tuned for more info ... but please know that it will be the Spring before I can do the testing. We will be using a fuel computer and an accurate inclinometer to reproduce the running angles and MPG values, before and after the upgrade.

Anyone who is interested in this potential and simple cost-effective upgrade ... please reply here. Cheers
Thanks for the quick response. I suspected what you said. The engines and props enter the water about 30" behind the hull because of the bracket. Am I still ok with the 24" X 9" with the water flow???
CaptainCrunch":w6ysaqql said:
Am I still ok with the 24" X 9" with the water flow???
Yes, I think you'd be OK even if they (OBs) were on the hull. Sounds like you're going to upgrade to Bennett ... about a dozen of us here have.
I have a 2510 MV and even though I love the boats' layout and style the ride was terrible in a 2 foot Chesapeake Bay chop. I put the 9 x 24 Bennetts on after discussing with Kevin (Megabyte) and Dale. I will tell you first hand it is totaly different boat and will eat up the bay now. I think on your DV they would be even better. It will be the best money you ever spend on your boat.

susqking":90ol5que said:
It will be the best money you ever spend on your boat.

I agree with Anthony. I replaced my factory installed 12x12 Boat Levelers with 9x24 Bennetts and the performance is like night and day. 8)
Dale, I would be very interested in the trim tab project.

Do you know of anyone with the upgrade on a 2520 DV? I have my 150's on the notch transom and don't have to use my tabs much. They do help in heavier weather.

I haven't been satisfied with the tabs on my new 2320 since I started running the boat. The boat was outfitted with 12x12 Lenco's which operate properly, but I think they are just too small. I recently bought larger Bennetts that I plan to install in the next few months. Obviously this will be a moderately big job, so if your "experiment" works out I may be interested in taking advantage of your research.

It is too bad that we all have to go through this since it would have been a no-brainer to install adequate tabs at the factory.

In anycase there may be a nearly new set of Lenco 12x12 tabs with switch and wiring harness available for sale when I get done installing my Bennetts.

Anyone interested?
Dale: I'm very interested in your project. I want bigger tabs on my 2520DV, but do not want to move the actuator or do a major overhaul to Bennetts.

Please let me know about your project details.

I have read with interest the information you folks have provided on Trim Tabs. I have just purchased a ’97 2520 MVSC with a notched transom holding a 200Merc. Dale I read that you are very pleased with the 9x24 tab but almost wish you had gone bigger. My boat is in the water (trailer being inspected) and I can’t do measurements right now so I will ask. Is a 9x30 tab an option? Do you think there would be significant improvement over the 9x24? Now is my time to make a decision. Comments appreciated.

Just know that I only wished I had gone bigger as my OB is on a bracket and therefore the entire transom is available to mount the trim tabs on. As is ... no, you do NOT in my experience really need to go any bigger than 9" off the hull (chord) and 24" width (span) tabs, for the 14 or 16 degree hull, maybe even the 21 degree model, but I've no experience with them.
I have a 1990 ..2510........notched transom w/ 066xsw ..250 Yamaha..I installed a pair of Lenco 9x24 trim tabs earlier this year. The tabs have changed this boat completely. It gets up on plane much easier, the bow stays down where it should, the gas milage has improved tremendously,
The handling has has gotten much better also. The tabs have paid for themselves many times over just in fuel expenses.
The Lenco system was very easy to install with great instructions. I would recommend them to any Parker owner. I think they are one of the best improvements that you can do to your boat for all around performance.

Did you replace existing tabs or add them? I could see the huge difference if you did not have tabs to begin with. Thanks for any info, but more details please.
I had none at all on before the install. I wrote Robin Parker and he suggested the 12x12 tabs that come stock on most new Parkers. My brother and I talked with several Parker owners, and most said that the 12x12s just were not enough. We ran into a angler in Dewey Beach this summer that had an older Parker with the same hull design as mine Modv. and he was running 9x24s. He had run 12x12 for years and changed them to the 9x24s and was very pleased with the improved handling and fuel milage and overall boat performance he was getting with just the change in tab size. I am using Lenco tabs and are very happy with them. There is a retro fit package if you are running Bennetts.
mildew2":2nr8wwx3 said:
He had run 12x12 for years and changed them to the 9x24s and was very pleased with the improved handling and fuel milage and overall boat performance he was getting with just the change in tab size.

Sounds like word is finally getting out. 8)

Switching from 12x12 to 9x24 tabs is probably the single best thing you can do to a Parker to increase performance. :wink:
I recently installed 12X24 inch tabs on my 2320. I am extremely pleased with the boat's performance since I made the switch.