NC11 best trim settings for cruising?

[richardc1]

Hi,
New owner of 2012 NC 11.

What do you find are the best trim settings for cruising?

- RPMs roughly 2,800 - 3,300?
- Lenco trim (flaps) up/off?
- I/0 trim around zero?

I've not had time to experiment yet, but would appreciate learning from this of you with lots of experience on the optimal settings.

I don't have fuel usage on my trip computer nor the auto trim function, so I don't have any data except speed optimization for a given throttle position.

Thanks for any help!

Richard.

[inewbie]

Hi I am no expert, and this is my first season as an NC11 owner, but here is what I am finding.

The boat feels a bit under powered which seems most pronounced with full fuel. So what seems to work best from acceleration on for me is to:

1) Set trim tabs to neutral
2) Initiate wide open throttle (WOT)
3) place tabs to full deflection when about 15 MPH is reached to assist "popping" the stern out of the water and facilitate getting on plane.
4) Continue to accelerate at WOT to 30 MPH or so, then back off to 3250RPMs (if I want to be efficient) or 3400RPMS (if I want to go fast)
5) Raise trim tabs to best speed and comfortable ride thereafter.

Hope that helps. My I/O trim sensor is out, so for now I just leave my engines at neutral.  When that gets repaired I will likely be able to eke a little more efficiency and speed. Though I have heard I/O trim does not matter much on the NC 11.

Mike

[richardc1]

Thanks, interesting point about D3-200 being potentially underpowered. I'm considering if changing the duoprops pitch from F5 to F4 might be wise. I don't really need the absolute top speed, and would prefer the boat not have to struggle with full fuel and cruising gear load.

[nc]

Hi
F5 are 23" pitch and F4 are 21" pitch, it is a 2" decrease, it is a lot
Before changing prop size, what are your WOT?( 4000RPM from Volvo specs)
Rule of thumb for a Mercury Mag350_2 2 ratio (5.7l) with a WOT at 5200RPM, 200RPM per non cupped 1", so on your boat you can expect more RPM change

[sjgoodwin]

Hi guys.  The most important thing on this boat is to trim the engines all the way as far down as you can.  I believe they go in beyond vertical so they actually trim the bow down.  I launch with tabs full on, them around 25 mph I back throttle to about 3000 rpm and let the tabs up until planed fairly level.  My usual cruise is about 23-25 mph and I get 2mpg which is also 2 L per mile.   Makes calculating consumption easy when you are nervous to get to the next marina!   That seat on the front bow sits right about on the horizon to my eyeline.   If you have digital speedometer then play with the tabs.   A few lights up or down will make the boat go .5 mph faster or slower on same rpm so you can optimize tabs.  

I generally would not run the diesels over 3200 very long as that was the advice from the dealer rep. 

[nc]

Hi
I made a mistake, less RPM change with lower WOT as D3 and result can be none proportional because it is a turbo diesel engine and the flat torque curve of D3.200 from 2000 to 3250RPM will change thing compare to gaz engine. Easy math tells for a 9% pich prop change, 125 to 150 RPM per 1" for 4000WOT, but flat torque curve will affect it.
Short story, if your WOT is 3800+, it is better to stay with F5, if it is below 3700, it would be an good improvement and should have be done as new, between 3700 and 3800, it is an expensive guest.

[richardc1]

I'm getting 3,930 rpm with light load.
Thanks for the info on F5 vs F4, I didn't realize that was such a big difference!
On my most recent boat that had bigger Cummins diesels, I had the props tuned to take the pitch down by about 1/2" from 24" to 23.5".

Thanks everyone for your input, really appreciated!

Anyone using the Volvo Easy Connect interface, and if so, can you get fuel flow data from it?

Richard.

[ian222]

I trim my drives all the way down (-5 on my gauges) and put the lenco trim tabs at full down position, once on plane running at about 3200 rpm I adjust the Lenko tabs a bit to level the boat. If I run at 3500 rpm I trim the drives up a bit and the trim tabs as well.

[richardc1]

Thanks Ian, appreciate the guidance.
Richard.

[Deleted]

Perhaps also check the negative tilt limit of your engine.
I found out long after delivery that his position could be lowered significantly (easy job on Zukes), increasing the tilt range substantially, and so giving more control of planing behavior in choppy conditions.