How to properly trim your boat with both engine and trim tab

[rsrutkowski]

Hi all..
I have a 2011 2120SC ( OMEGA lll) with a Yama 150 / 9.9 and factory trim tabs.
I would like to know how you guys like to use both the motor trim and your tabs for best performance.
When I start from a stop I drop my tabs all the way down, have the motor tucked all the way in ( down ), power up til I get on top then
adjust the tabs to level out ..usually about half way down according to the vertical line of red LEDs on the trim tab indicator.
I feel that I am missing something by not incorporating the motor trim in addition to the tabs.
I usually run heavy with 50 to 70 gal of fuel, a 32 gal bait tank and one or two other guys ..and a bunch of gear.
Looking for pearls of wisdom..

 

[DaleH]

While I don't run that hull I'd start with your trim tabs 1/2-way down and try that, with the motor tucked in. As she starts coming up onto plane you can start trimming your OB out. I back off my tabs as much as I need to for the sea state and most times I run at zero tabs, or maybe to 3 (scale goes to 20).

Trim the OB out until you 'hear' the OB start sucking air and/or RPMs increase without you advancing the throttle, then tuck it back in a tad to stop that ventilation. Then, if needed, tweak for tabs for the sea state. After a while you'll get an automatic sense of how much trim tab you need to get the hull to ride as you want it too.

Sounds like you have been running the boat with the OB still tucked in ... that is a HUGE killer to fuel efficiency ...

Hopefully some other 2120 SC users (Sully?) will chime in ...

 

[Sully]

I usually run heavy with my boat
Dive gear and people cooler full 8) and gas
I usually run motor all the way down being so back heavy and adjust trim tabs
For full economy depending on what RPM I'm running
I use the Yamaha Fuel management gauge to dial it in for best fuel at given speed
usually around 4K 25mph at 8 GPH on my 200HPDI
Yamaha Fuel management gauge one of the best things I bought!

I think Dale's advice is also good depending what is the boat at the time
I run my friends 2520XL and I run it like Dale mentioned
The 2120 I feel usually is sitting low in the water due to limited size with less beam then the 25
So she planes sooo much easier not to forget my friends and Dale have a modified V also changes things

I have been looking at this set up maybe next year..
check out the Vid on the left
http://www.lencoautoglide.com/

 

[rsrutkowski]

Thanks guys..I also use the GPH and ECON gauge to fine tune....great for fuel management...4000 to 4500 generally best econ but sometimes better MPG at 4900-5000 depending on seas...wouldn't have that data without the Fuel Management Guage
I would think the tabs add drag at some point thus lowering the economy..the 21 is a bit stern heavy with the 9.9 and bait tank... I really need full tabs to get on top..I'll play with the motor trim some more...
Looking forward to more input esp from 2120 SC owners

 

[Luv2fish]

I start out like you do with the tabs all the way down and the motor trimmed tight. The next thing that I do, as Dale mentioned, is trim the motor up until I notice it is making the sucking noise. I then just drop it back a bit so it is digging full power. Usually at this point my boat will be listing one way (port side down). For some reason as I tilt the motor up the boat lists. Of course this is impacted by the load and where the passengers are sitting as we head out. I then adjust trim tabs to even out the boat and get some of the pressure off the bow. Depending on seas and load this is ALWAYS different. The trim of the motor is always a bit different depending on situation.

I don't think there is a standard setting as load and seas impact this no matter where you are. I start with the motor trim and then end with the tabs, always starting out of the hole shot with them all the way down.

After 3 years now I can "feel" when it is right. Unfortunately I do not have the fuel management system that you do so I'm not dialing it in a fine as you are.

Steve

 

[DaleH]

2 things ...

This is where (1) wider tabs shine ... as they create LESS drag to get the desired tab effect vs. the woefully undersized tabs most boats (all brands) leave the factory with ... and (2) using the fuel computer set to direct MPG readout, I can dial in a 10-20% improvement in fuel economy.

 

[rsrutkowski]

Good stuff...looks like I need to bring the motor up as part of the adjustment procedure...
and yes it's always changing....

 

[Sully]

Dale has a great point.... I'm getting wider tabs next year was on the list....
Will get much better lift in back and wont have to bury the motor as bad
And have more tab left over when I need it

 

[DaleH]

Dale has a great point.... I'm getting wider tabs next year was on the list....
Will get much better lift in back and wont have to bury the motor as bad
And have more tab left over when I need it

And get SIGNIFICANTLY better fuel economy ...

 

[rloomis]

Like Dale said, 0 tab is where you theoretically should get the least drag, so using no
more tab than you need should give you best economy.
For engine trim, it's all about thrust angle: the closer to level you can get, the more you're using
your thrust to drive the boat forward instead of lifting the stern.

My 2120 has a heavy engine (F225) and large bait tank so she's definitely heavy in the stern.
So she likes to run with a little bit of down tab for best ride and economy.
There's a lot of variables: engine height, center of gravity, type of prop, sea conditions, how
fast you're going, etc.

Negative engine trim will lift the stern and keep the bow down, but tends to drive the bow
down under power. If you're pile driving the bow into a head sea, you'll want to trim the motor out
a little and use tabs instead to "plane" the bow into the waves for a easier ride. Depending on
speed and sea conditions, you'll want to play with tab/engine trim to find the sweet spot for how
much "driving" the bow down vs "planing" the bow down will keep the bow slicing through the waves
without slamming. The faster you're going, the more efficient tabs get, so you'll need less at higher speed.

In a following sea, you should keep the tabs up and use more negative engine trim to control broaching.
You want to keep the bow up in a following sea and avoid driving the bow into the swell in front of you.
By keeping tabs up and engine down, you can use the throttle to very quickly control driving the boat down
the face of a swell you're riding, and backing off the throttle to let the bow ride up before hitting the swell in
front.

 

[rsrutkowski]

rloomis..
...good point about a following sea.....
Thanks to all for the input..