Poor planing, bow up attitude solved

[Tom3298]

I recently bought a 2000 340 Sundancer, 7.4L MPI inboards. I was ready to sell it due to incredibly poor planing and difficulty getting on plane. The bow was so high when on plane I couldn't even see over it without standing up or sitting on about 5 cushions. The factory installed trim tabs were so pathetic, I could barely tell when they were full up or full down. After doing lots of research, I learned that Sea Ray installed Bennett trim tabs that had only 50% of the marine industry recommended surface area for a 34' boat. No wonder the factory installed ones made virtually no difference either full up or full down. I replaced the factory ones (12" x 16") with Bennett 12" x 24" tabs. WOW! I've got a new boat. The tabs actually move the boat from bow up to bow completely down. I no longer have to stand up to see what's in front of me. Why Sea Ray didn't install the correct tabs is a mystery to me. It was an easy install since I didn't have to move the actuators from their original position on the transom. No drilling new through holes in the transom. Even though I replaced the factory Euro style rocker switches with the EIC rocker switches, that wasn't necessary. Just something I wanted to do. For under $250, I now have a boat that handles like a dream, not the pig that it was before.

 

[Tabman]

Delighted to hear about your results Tom, thanks for sharing!

Tom
Bennett Marine

 

[hottoddie]

This is a very common problem with V drive express cruisers, not only Sea Ray. If you saw the tabs I have installed on my 390 EC you'd think I was nuts but almost all of the 390 EC owners in this forum have done something similar. Ya Sea Ray should know better.

 

[Alegria]

I have a 330 and feel your pain. This might be a winter project for me. I don't even think I have 12x16 tabs on mine!

Thanks for sharing!

Sent from my AT&T LG3

 

[Gofirstclass]

Tom and Tabman, is it necessary to install new actuators, or is it possible to simply attach larger plates to the existing tabs?

When I bought my 550 they installed a huge swim platform. The platform was so long (front to back) that the rooster tail would hit the bottom of it when we were on plane. They needed to move the rooster tail aft about 10"-12" so to accomplish that they engineered a "hull extension" that added about 16" to the planning surface. They also attached extensions to the trim tabs to make the longer (front to back) as well as wider.

That solved the problem and it seems the addition of the hull extension has provided enough additional lift that I seldom ever use the trim tabs. The only time I lower them is if I'm running with full fuel (700 gallons) and full water (200 gallons). After I've burned off about 1/4 of my fuel load and used up some of the water I don't ever have to use the tabs to keep the bow down.

Here's a photo of what they did, You can see the extension they put on the bottom of the hull as well as the tab extensions. Now when I'm getting on plane the rooster tail comes up just about 8" aft of the swim platform and when running on plane it's about 12"-15" behind the platform (depending on fuel load, etc.)

 

[Tabman]

Bennett actuators are pretty rugged and usually can be left in place when larger Tabs are installed up to 42 x 12 inches, then 2 actuators per Tab are used. But they need to stay in the center of the Tab side to side.

Also while may folks have added more that 12" of chord (fore to aft) measurement with good results we cannot recommend that since it increases the strain on the actuator. Particularly when backing down since water can pile up on top of the Trim Tabs forcing them down and possibly damaging the actuator. This is exacerbated by a large swim platform that can trap more water when backing down.

One option is to use the tab retention devices that are often used on sportfishing boats that back down hard.





They are designed to take the strain off the actuator when the Tabs are forced fully down in a hard backing situation.


If at all possible adding more span (side to side) is the way to go or even adding another pair of Tabs inboard of the existing ones. Sort of like your photo, but with operating actuators teed into the other ones.

Tom
Bennett Marine