Can i make these trim tabs bigger?

Siboatguy

Active Member
SILVER Sponsor
Mar 28, 2016
499
Holmdel,NJ
Boat Info
1999 Sea Ray 290 Sundancer
2005 Sea Ray 320 Sundancer
2005 Sea Ray 340 Sundancer
Engines
Twins V-Drives
8.1 Mercruiser
Is there anyway i can make my tabs bigger from (bow to stern)? And will that help?? I have a sea ray 320 props are redone. This year im gonna add 4 blades... I notice i always run bow high and gotta run at 3900 to stay on plane with out the ass sitting down... Was thinking of just welding a piece of stainless steel sheet metal on the bottom of it and turning the sides down?? If i change the trim tab and make it longer i was worried the piston won't be long enough...
tabs1.jpg
tabs2.jpg
 
I had my trim tabs enlarged both front-to-back and side-to-side. I also had a hull extension made to increase the running surface of the hull but that was not done for increased lift.

So, the simple answer to your question is "yes you can" enlarge the tabs.

Trim_Tabs_and_Hull_Extension.jpg
 
There is a guru of Tabs that is on several forums.

Tabman

I would see if you could get his input. Have seen him on here and some other forums. He helped me with some tab reconfiguration work last fall. He knows his stuff.

Mark
 
I'm hoping i hear from him tabman.... I would love to hear his input on it... Thanks again everyone for all the help....

If i do add to it... curious if i should turn down the sides and if so how much and how much to add on... How much can the pistons handle...
 
While I seen successful instances of adding chord (fore to aft) to tabs by adding an extension to them, I can't "officially" recommend it. While the actuators are very strong, they can be damaged by the additional leverage. Particularly when backing down, as water "piles up" on top of the tab. This is exacerbated when there is a platform on the transom that forces even more water down when in reverse. 12" chord Tabs are the maximum we recommend.

The addition of 3" drop fins is a good idea.

Also I don't recommend welding as it invites corrosion.

One idea would be to add Tabs over the prop tunnels and simply tee them into the existing actuators on either side.

I hope this helps,

Tom McGow
Bennett Marine
 
While I seen successful instances of adding chord (fore to aft) to tabs by adding an extension to them, I can't "officially" recommend it. While the actuators are very strong, they can be damaged by the additional leverage. Particularly when backing down, as water "piles up" on top of the tab. This is exacerbated when there is a platform on the transom that forces even more water down when in reverse. 12" chord Tabs are the maximum we recommend.

The addition of 3" drop fins is a good idea.

Also I don't recommend welding as it invites corrosion.

One idea would be to add Tabs over the prop tunnels and simply tee them into the existing actuators on either side.

I hope this helps,

Tom McGow
Bennett Marine

Thanks so much for looking into this tom (Tabman) The tabs over the prop tunnels don't know if i wanna get into that much work this year... Lets say i leave them that size maybe only go 3inchs longer but mostly add the drop fins.. Do you see a big difference from just drop fins? Ill just bolt on to the org trim tab.. unless i should buy a hole new tab?
 
Thanks so much for looking into this tom (Tabman) The tabs over the prop tunnels don't know if i wanna get into that much work this year... Lets say i leave them that size maybe only go 3inchs longer but mostly add the drop fins.. Do you see a big difference from just drop fins? Ill just bolt on to the org trim tab.. unless i should buy a hole new tab?

They help quite a bit. The Bennett part number for them is DF12 https://www.defender.com/product.jsp?path=-1|2331321|2331349|2331353&id=2393734

Tom
Bennett Marine
 
I had 1/8" stainless plates made that I drilled and bolted to my existing tabs. The plates were about 4” wider, and 2” larger fore to aft. I also added the 3” drop downs as tab man suggested. This helped. I have a 30’ with twin i/o’s and a generator. There’s a lot of weight in the back end. I still run around 3500 though. The big difference is getting on plane when I’m loaded up.
 
Something else kinda odd on your tabs, looks like the anode is mounted on the bottom of the tab, not the top?
 
I see that all the time. Standard procedure is to install on the top of the tab only. Putting one on the bottom interrupts the flow of water and reduces the effectiveness of the tab.
 
Smaller boat and with IO so sort of apples to oranges but I added the drop fins to our 290 in combination with 4 blade props and dropped min planning rpms by about 500
 
Hi looking for some help on a 1999 340 sundancer 7.4 vee drives, I am looking for idea’s on reducing fuel usage and best RPM for running at 27 to 30 MPH, I am on the St Lawrence river
 
Same here. Planning to pull my 340 this year and want to have new tabs or parts to make tabs better ready to install. So what’s the best deal. Extend and the side fins?
 
I did drop fins first and see what that did... It Def helps and i do notice a big difference. Thanks Tab man...

IMG_0620.jpg
IMG_0625.jpg
 
What kind of boat? And any pics of the bottom side of the tab? Do the bolt heads not stick out in the way?
 
If you use pan head, or round head machine screws you will be fine. To the other posters if you post pictures of your existing Tabs that would be helpful in making recommendations.

Tom
Bennett Marine
 
Hi looking for some help on a 1999 340 sundancer 7.4 vee drives, I am looking for idea’s on reducing fuel usage and best RPM for running at 27 to 30 MPH, I am on the St Lawrence river

Mine is basically same engine Hull etc. Fuel usage is hard to lower appreciable. It’s just expensive hobby. On plane at 3400 rpm is my sweet spot. It’s about 30 mph for me and about 1 mpg (imperial gallons). Fuel burn goes up if I run slower or faster. Next best economy in mpg is cocktail speed but before it starts to plow. Maybe 1200 rpm max. But that’s too slow if you need to get anywhere.

Fuel is one of the smallest costs of ownership of a boat and the only cost that means you are enjoying using the boat.
 
I have a 2002 340 only pic I have it tabs is this.
I also have to ask the down bolt ons how will that work when you slide it on a trailer...
 

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