Trim Tab Change WOW!

GeeBee

GeeBee

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Just got my boat (98 SeaRay 270 Sundancer) back from the yard. Had to install a new Bravo III drive. The old one was 17 years old and it started making metal. So naturally there was a nice performance kick but the big thing was the trim tabs.

Came stock with some 12x12 proprietary (made by Bennett tabs. In consultation with Bennett I went to 12x18 stock tabs. The yard was non plussed on my plans, but I told them to do it anyway.

WOW! Nice stern lift, very good control, fuel consumption way down (about 15% for the same speed), speed up for the same rpm. It is almost too powerful now in that you can start to make it bow steer if you over do the drive trim and the tabs. I suspect manufacturers don't want that so they under tab the boats. It is like a brand new boat. I can smack out 32 knots without breaking a sweat.
 
Congratulations! Great Upgrade, Results, and Report! A couple others here have made big gains by enlarging their tabs, one way or another. We have Bennett's on our little 215/EC. I use them to plane heavy loads, then usually retract and use only for side-to-side trim. Maybe I should re-think...
 
quote:
Originally posted by GeeBee

...I went to 12x18 stock tabs...

Click to expand...


12 = span and 18 = chord or vice versa? Just curious.

I enlarged mine from stock 22x9 to 22x18 and got the same great results. For whatever reason, on the 330 Sea Ray the stock tabs were terribly undersized.

With the cost of fuel what it is, I hope others consider the change.

Glad it worked out for you.
 
Great info Greg. Too little discussion of tabs and the many boats I see plowing along with the bow way up seems to indicate that lots of owners don't have or use them.
 
quote:
Originally posted by pdecat

Great info Greg. Too little discussion of tabs and the many boats I see plowing along with the bow way up seems to indicate that lots of owners don't have or use them.

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Or the boat was undertabbed from the factory for whatever reason. I'll venture money. Fully loaded, I had to run full tabs all the time to keep the nose sorta over. Friends with the 7.4s in the same boat had the same problem. With the larger tabs, I have to be very careful at the start of each season to not stuff the bow.
 
I just bought a 24ft pocket cruiser with trim tabs (my first) and have seen lots of differing opinions on how to use them. What position should they be in when idling out from the slip? Should they be full up, down, or level at idle speed, and set where when powering up to plane? Thanks!
 
I leave ours Up/retracted off plane. I tend to tuck the outdrive In to achieve plane unless the boat is heavily loaded (like 4 big POB in our 21-1/2-ft pocket cruiser. Then I use them a good amount Down (as in Bow Down on the control panel) and retract when up and running. Earlier discussion makes me wonder if I should use them for more than lateral trim once on plane. And you question makes me wonder about idle speed... Like many single engine I/O's, our Sea Ray wanders at low speed. I don't know if "dragging" both tabs (Bow Down position)would help with that but I think I'll try it.

IF you've wondered, the Switches on the Control Panel are actually cross-wired. The way to bring Port Bow Down is to bring the Starboard Stern UP. So the Left Hand Switch controls the Starboard tab, and vice versa.

Just be SURE that if you Trailer or use a High and Dry, to fully retract the Tabs before loading the boat or having the marina put the fork lift under it. Some systems automatically raise the Tabs when the Engine is not running...
 
I have a same boat as jd, just different year. I have Bennett Auto trim taps and use to set them at "Auto" mode. At idle, both taps were down all the way and with the drive tucked in, the boat jumps on plane in no time, while trimming it out, both taps are also tries to level the boat out so, boat gets up and level out in just a matter of seconds.
 
DeeVee, we should establish a 215EC Support Group. Anybody who tries to work in the Engine Bay of one...

Does yours wander off course at low speeds with your tabs down?
 
With taps down and drive tucked in, very little to none compares to taps up.
 
I will try that! Right now the boat is on the trailer for outdrive work and I'm down harder than that. Heart surgery a month ago. About 60 more days before I can do heavy mechanics and run the boat. They cracked me and it needs to heal. But I'll remember your advice, thanks!
 
When still running the 454 Crusaders I went from 22x9 to 22x12 WITH DROP FINS.

When the boat was fully loaded, I was able to document the performance difference with my GPS & Floscan.

The interesting point here is that after the repower to diesels, the tabs make zero, THATS RIGHT ZERO difference in performance/economy/speed.

I can only surmise that the bigger props and increased torque with the diesels are creating more LIFT, getting her a$$ out of the water with a better running angle.

Bennett and TABMAN truly ROCK !

RWS
 
RWS Did running angle change?
Are the diesels heavier and move the weight more forward?
 
"Are the diesels heavier and move the weight more forward?"

a typical Yanmar 315 hp install will weight equal to or less than a big block gas install when you take into consideration all the stuff that goes along. The 300-400# loss of weight from gas to diesel (in this case) is not really a significant number when you consider that amount of weight is often changed and carried aboard in daily passengers and products. I believe the larger slower 4 blade props make the largest difference and would agree with RWS based upon my observations of swaps.

Trim tabs are solving for a balance issue which is good but there use also adds to inefficiency and there heavy use scan often lead to real problems in following seas.

Hope this helps
 
I guess every boat is different. Mine went faster with full tabs at same high cruise rpm in flat seas.
 
I'd like to make this improvement to my boat - did you guys have to buy the hydrolic ram or can the tabs just be purchased and the old ram used?? I would go up just one size.
 
Those light weight high speed diesels are pretty amazing. Close to the weight of "marinized" gas truck engines. I don't know what the HP is, neighbor bought a gorgeous 35-ft Cabo, used. CAT power. He mentioned the engines weigh 8,000 pounds, and that's each.
 
David, 18" span. 12 chord.

I truly believe that the manufacturers intentionally under tab boats out of fear their customers will mishandle them. I think it is a valid fear. For the experienced, it is pleasure to run a well tabbed boat. I run an ATC system with an auto tab retractor. Works great!
 
About 75% of what I do on the internet is help people fit larger Trim Tabs. As you can see from this great thread it's worth it. Just have to use them in small bursts and let the boat settle down before making another change (or get the ATC)

Rum Diet,

What kind of boat do you have and can you tell us the size Tabs on their now nd if they are Bennett?

Tom McGow
Bennett Marine

quote:
Originally posted by RumDiet

I'd like to make this improvement to my boat - did you guys have to buy the hydrolic ram or can the tabs just be purchased and the old ram used?? I would go up just one size.

Click to expand...
 
quote:
Originally posted by GeeBee

David, 18" span. 12 chord.

I truly believe that the manufacturers intentionally under tab boats out of fear their customers will mishandle them. I think it is a valid fear. For the experienced, it is pleasure to run a well tabbed boat. I run an ATC system with an auto tab retractor. Works great!

Click to expand...


How did you find the "sweet spot" for the ATC? By feel or fact? ie. Feel is feel....engine labor, rpm..... Fact is FloScan or the like. I ask because I've heard from those who like the system and those who do not. IMHO, every dime not in the gas tank, is a dime at a restaurant. Spreading my meager wealth so to speak.

TIA
 
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