Use of Trim Tabs on 340 DA

[Bounty]

Bounty is a 2000 340 DA. I would like opinions as far as the use of trim tabs is concerned. Bounty does not have trim tab meters, and typically I use the tabs to level the tilt of the vessel, but not to get on plane or even push the bow down much. I would appreciate any tips as to the proper use of the trim tabs.

 

[fwebster]

Tabs create drag so as a general statement, your boat is more efficient when you do not employ the trim tabs. Obviously, there are exceptions to this statement and those exceptions are usually dependent upon your boat, the specific model and the way you have it loaded.

Most mid-sized and larger express style Sea Rays plane smartly and you normally don't need tabs. An exception may be if your particular boat has excessive bow rise or if you cannot see over the bow as you accelerate. A very few DA's do seem to plane quicker and run faster with partial tabs deployed. The speed differential is in the 1-2 kt area so its not very meaningful.

On i/o powered boats it is usually better to start with the tabs completely retracted then get the boat stabilized on a plane before applying trim tabs. If you get the outdrive trim and trim tabs working against each other the boat can get squirrely. Stabilizing the running angle before applying tabs usually saves the squirrel chasing.

Trim tabs on DA's seem to be most beneficial for balancing out load differentials to avoid a list underway. Correcting a list will make a boat run considerable faster since it significantly reduces the wetted area of the hull and therefore, drag.

Hope that helps..........

 

[Turtlesboat]

I use the tabs a lot now, maybe I really want a trawler... but I push the tabs down and cruise a slower speeds. When I want to get up and go, I rarely use the tabs except to right the boat. but for a long cruise in roughish water with my size boat, I tuck the drives in, push the tabs down and cruise at about 15mph. I love the way the boat feels this way, slow, smooth, and stable. I know the tabs are mainly used to control list but for slower speeds they work great pushing them down.

 

[Alex D]

The 340DA is tail heavy. I have played and observed tab reaction a lot on our 340, so here is what I do.

First, to figure how the tabs extend I counted how many seconds it takes for the tabs to fully extend ( sitting in the water whilemy wife operated the switches) since I don't have a tab indicator either. It's about 12 seconds for mine in or out and the action is linear. So that gives me an indication when I run how far they are extended.

Running the 340 at 3000 rpm is painful. You plough a lot or need lots and lots of tabs to run remotely efficient. 3200 rpm and up to 3600 rpm you need some to no tabs. I know that between 3200 and 3500 rpm the 340 needs about three to six seconds of tabs to run most efficient. More people, more tabs of course. I have now figured a bow rail position relative to the horizon where the boat runs most efficient (indicated by max speed at the same rpm setting) and I can tell you the 340 needs quite a bit of tabs to run most efficient up to 3500 - 3600 rpm and 29 to 30 mph when it begins to run most efficient without any tabs and only needs tabs to level it out.

Having been on 380DAs and 410 DAs I can tell you that even with gassers these boats plane better and without a lot of tabs, especially the 410 which is a very well balanced boat (only have gas engien experience on the 410 and 380 though).

 

[Bounty]

The 340DA is tail heavy. I have played and observed tab reaction a lot on our 340, so here is what I do.

First, to figure how the tabs extend I counted how many seconds it takes for the tabs to fully extend ( sitting in the water whilemy wife operated the switches) since I don't have a tab indicator either. It's about 12 seconds for mine in or out and the action is linear. So that gives me an indication when I run how far they are extended.

Running the 340 at 3000 rpm is painful. You plough a lot or need lots and lots of tabs to run remotely efficient. 3200 rpm and up to 3600 rpm you need some to no tabs. I know that between 3200 and 3500 rpm the 340 needs about three to six seconds of tabs to run most efficient. More people, more tabs of course. I have now figured a bow rail position relative to the horizon where the boat runs most efficient (indicated by max speed at the same rpm setting) and I can tell you the 340 needs quite a bit of tabs to run most efficient up to 3500 - 3600 rpm and 29 to 30 mph when it begins to run most efficient without any tabs and only needs tabs to level it out.

Having been on 380DAs and 410 DAs I can tell you that even with gassers these boats plane better and without a lot of tabs, especially the 410 which is a very well balanced boat (only have gas engien experience on the 410 and 380 though).

Great info. Thanks a lot!