Running with trim tabs down

[allan1]

I have a 2002 Dancer 340 with the 6.2 gas motors. When i drop the trim tabs down and run the boat on plane the speed on the GPS increases and the boat runs great. I have V drives so I assume that with the trim tabs down the props are running the boat on a straighter plane. Did anyine else ever try this. My fuel consumption does not seem to be any worse than running with the tabs up.
When I try running with the tabs up and full of fuel the bow is to high and it does not ride as good.

 

[Havana Shamrock]

I have a 2002 Dancer 340 with the 6.2 gas motors. When i drop the trim tabs down and run the boat on plane the speed on the GPS increases and the boat runs great. I have V drives so I assume that with the trim tabs down the props are running the boat on a straighter plane. Did anyine else ever try this. My fuel consumption does not seem to be any worse than running with the tabs up.
When I try running with the tabs iup and full of fuel the bow is to high and it does not ride as good.

I am also trying to figure out if i should retract them after planning i tried it and the boat stayed the same so i thought i was running more efficient?

 

[MAKC]

I run with my tabs down which gives me more speed. The results you are getting with running with them down have been seen by many others with the 320/340. I use my tabs almost full down to get on plane and then retract them to about half way when im cruising. I run about 3600 rpm and about 25mph on the GPS. When i run with no tabs, my speed actually slows and i have to give it more throttle.

Mike

 

[Hampton]

Normally, on the 340, tabs up is best. They are not needed to get on plane - they don't even help that much at all. I put them down on one side or the other to level the bow with the horizon.

EXCEPTION: Yesterday, we ran with almost full tabs down for almost 7 hours. We were heavy, seas were moderate, and tabs down really made a diff to keep us on plane when a large wave tried to knock us back to schlogging. It was bad enough that I noticed that when my wife left the helm to rest on the back seat, I needed some more tab down to get back 1mph that I had lost.

I agree that with the 320 tabs are more useful. The 02 340 may very well be the same for the same reasons - more similar boats.

 

[Havana Shamrock]

Am I getting worse gas mileage by leaving them down? I cant really tell if theyre 1/2 up or down just full . is there a proper way to run?

 

[Turtlesboat]

I run my 450 with almost full tabs. I'm butt heavy with the TNT and dink on the back. I would say run it where it feels good.

 

[allan1]

Thanks for all the input. Some may say that sounds crazy, running with the tabs down however just try it. One thing I did not mention was that I did not like the feel with the stock tabs as it did not react very much or at all. I installed the trim tabs for a 02 Dancer with deisels. There wider and longer and make the boat react like trim tabs should I got the part number from the parts manuel with the boat. They bolted on using all the same other parts. I love my Searay and I think this is the only mistake Searay made when building this model boat. With the tabs down, I pick up two to three miles per hour (GPS) and do not see any more fuel consumption.

 

[Alex F]

I can't speak in regards to 340s but here's my response on 320s. As with most non-trivial questions I'd say the two words answer is "it depends"....Yes, it depends on many different variables. The basic approach I've noticed, which others also reported, is the slower you go (lower end RPMs) the more tabs you'll need to stay onl plane and have better efficiency. This applies to riding rough seas (just as John had mentioned). When I keep her under 3500RPMs the bow goes up more as the stern "drags" more and deploying the tabs helps to level the boat providing more effecient ride. If I need to go slower ~3400RPMs I need to deploy full tabs otherwise besides not efficient ride she would eventually fell off the plane. However, on the other hand if you add RPMs and encrease the speed ~3600-3700RPMs or more in relatevelly calm seas the boat performs better with no tabs (taps all the way up). If I apply tabs at speed/rpms (3650-3750RPM @ 22-24knts or 25-27MPH in normal seas conditions) I can see that she slows down a bit.

I remember that while riding my 240DA with tabs up and drive at proper angle I would gain ~4MPH vs. having the tabs down. I'll never forget the pre-purchase sea trial on 240DA how both the surveyor and the broker couldn't get her reach over 4500RPMs. I asked to take take the helm and I brought her to 4800RPMs in not calm seas (2-3 footers) by properly adjusting both the tabs and the drive.

I don't remember exact difference on 320 but I think it's around the same 3-4mph.

Having seen most 340s with larger engines than 6.2s, IMO the smaller engines need to run at slightly higher RPMs to maintain the same ride with larger engines at lower RPMs. Just my .02c.

 

[VinceR]

My 7.4, v-drive 2001 340 runs best on plane with the tabs down.

 

[Alex F]

My 7.4, v-drive 2001 340 runs best on plane with the tabs down.

I begin to sense that the reputaion 320s carry riding bow high may also apply to 340s as well. :huh: It's just we didn't know that 340 owners are hiding this by keeping the tabs down :grin:. On a serious note we need more responses from 340 owners to make such conclusion.

 

[Skuza]

This really puzzles me. I adust the tabs almost every time I go out trying to find max speed which I think would be max efficiency. Never have I found full down tabs to be most efficient. It labors the engines and plows the water. Yes it smashes the waves a little better than banging over the top of them but I rarely am in such conditions. What am I missing here???
For a reference I managed 26mph at 3400rpm full of fuel and water this past weekend.

 

[CAMELLA]

I have I/O's in my 340 and the stern is heavy. Tabs down to get up on plane and if the water is smooth tabs fully up and only used for leveling. If the bay is rough which is usually is tabs down. If I'm under 3,000 RPM I come over plan with or without tabs.

 

[BahamasBlair]

Guys,
On my 340, I always run with the tabs down at least half way if I have a full take of gas (225 gals). That extra weight seems to make the boat heavier in the aft sections. I get around 3 extra MPH for the same amount of throttle which translates into a bit of fuel economy. Once I get down to a half tank of fuel, I tend to run without the tabs and use them only to balance the boat if we have crosswinds.
Also, at any speed below 3300 rpm the boat runs better with tabs down regardless of how much fuel we are carrying. Hope this helps a bit.

 

[billnpat]

Normally, on the 340, tabs up is best. They are not needed to get on plane - they don't even help that much at all. I put them down on one side or the other to level the bow with the horizon.

EXCEPTION: Yesterday, we ran with almost full tabs down for almost 7 hours. We were heavy, seas were moderate, and tabs down really made a diff to keep us on plane when a large wave tried to knock us back to schlogging. It was bad enough that I noticed that when my wife left the helm to rest on the back seat, I needed some more tab down to get back 1mph that I had lost.

I agree that with the 320 tabs are more useful. The 02 340 may very well be the same for the same reasons - more similar boats.

HOW ABOUT THE 2002 310 ??

Tabs are useful?

 

[Alex F]

HOW ABOUT THE 2002 310 ??

Tabs are useful?

Bill,

In general, trim tabs are usefull for any model and I would guess for any size of a planing hull boat.

 

[billnpat]

Bill,

In general, trim tabs are usefull for any model and I would guess for any size of a planing hull boat.

Usually most times its just the admiral and myself on board,

so when we would use trim tabs im not sure :huh:
we seem to be ok with them straight out...

 

[JimT]

Usually most times its just the admiral and myself on board,

so when we would use trim tabs im not sure :huh:
we seem to be ok with them straight out...

Set them all the way down to get on plane. Then adjust for the best performance based on actual conditions.

 

[billnpat]

Set them all the way down to get on plane. Then adjust for the best performance based on actual conditions.

Adjust them while on plane......GOT IT....:thumbsup:

Thanks....

 

[allan1]

After reading all the posts I did not mention one thing that i did to my 340. I installed trim tabs from a diesel. They are bigger and the results is I can really adjust the attitude of the boat and feel the tab results easy. I got the part number from the owners parts manuel. They are wider so you have to drill a couple of holes. Everything else stays the same. Every boat I ever owned with trim tabs was easy to feel the results. The 340 does not give me that same feel so the diesel tabs really work well for me. Tabs down, + 3.0 mph and no fuel consumption difference.

 

[tobnpr]

Been discussed before, every boat is different.
My 390 requires full tabs all the time.
After planing on full tabs, note your rpms and gps speed. Slowly raise both tabs a bit, wait a few seconds and check gps speed again. Repeat. Find the setting that results in the greatest speed.

Tabs create additional drag. With stern-heavy boats, the improved running angle more than offsets the drag and increases speed and performance.