Cruise-On Plane Best Configuration Feedback Please

RVPilot

RVPilot

Member
Sep 11, 2020
62
Olympia WA - Puget Sound
Boat Info
1999 270DA
Engines
7.4 Merc MPI B3
Hi Folks ... LOVE to get some feedback!!

We are new owners of a 1999 270 Sundancer, running a re-powered 7.4 with 115 hours on her clock. Todays outing was with full fuel, full water, 2 adults, and one English Cocker Spaniel ;=}

Perfectly clear winter day in Portland, Oregon, 50 degrees ... 10 kts wind from the west with light wind chop and some 1-2 foot wind waves. We are out on the Columbia River for our 6th cruise since bringing her to Oregon.

I've found that to get on plane, I have to accelerate at 3500 rpm, then the bow drops once on plane, and we throttle back to 3200 which seems to be comfortable. About 27-28 MPH.

I've read that to be more efficient through the water we could be trimming the outdrive UP to the 1/4 mark, so we did that today, and two things happened ... (1) the PRMs increased to 3450 from 3200, and (2) the bow rose slightly. Speed seemed to NOT change.

So are we configuring to be on plane correctly?

What effect does trimming the outdrive up provide on efficiency and performance? Other than the 200-250 RPM increase, we didn't notice anything demonstrative.

Love to get tips, pointers, and feedback!
Thanks ...
 
I make an adjustment and check the speed on the GPS. Trim tabs all the way up or to keep it level left and right. Then add some tabs to see if it picks up or slows down. Same with the drives in or out a little bit. I try to keep both engines around 3,000 rpm or below depending on the load. The GPS is your best tool because you want to maximize MPG OR you want to make it comfortable to get through bad chop and I don't really care what the GPS says in those kinds of conditions. A lot of time a quick lip on the tabs raises or lowers the speed by 1/10 of a mph, so I keep going until I can squeeze anymore out of the current engine RPM's.
 
After I'm on plane I retract them and add enough to level left right. THEN, I'll start punching some back in to bring the bow down. I keep doing it until it's unproductive. I trim the motor out a little as well. You just have to mess with it and you'll see those little changes on the GPS without touching the throttles. It's not uncommon after getting on plane to gain another 1 to 2 mph without touching the throttles. I'm ALL for maximizing MPG!!!
 
‘Typically’ once on plane you want tabs up and only use to balance side to side. But if in a chop you may want some trim down to help keep on plane or smooth the ride.
There is no one size fits all rule. Varies by boat, rpm, water condition, weight on board, yada yada. Play with it, you’ll figure it out.
 
I feel the primary reason for tabs is to obtain the max speed with the least rpms. They also can influence ride comfort and safety.
Years of use on my 20 ft i/o showed me the theory matches the reality. I set the tabs full down, once out if the hole and on a plane decrease to target rpm, then raise tabs till speed no longer increases. On glass smooth days often found I could lower rpm even more to keep at target speed. If bow starts to porpoise up and down,lower tabs till it levels out.
Bigger heaver boats may be less responsive or maybe harder to feel changes.
Hopethis helps some.
 
I can’t offer any additional advice. However, since I also have a 1999 270se Sundancer and an english cocker, I believe you’re doing the important things right!
 
We knew the boat was right, and adding Kiki was a bonus ...
IMG_6862.jpg
 
I don't know if this will be optimum for your boat, but here was my routine with my last boat (25ft deep V hull, 350 engine with Bravo 2 drive):
Getting on plane:
- Drive trimmed right down
- Tabs set for bow down on the starboard side (Single prop Bravo 2 caused a lean to port underway).
- So about half tab on the left side switch, full down on the right side switch
As soon as it was on plane:
- I trimmed out the drive till the prop starts to ventilate (you hear and feel it) and then trim back down a bit.
- Then I adjusted the tabs up a bit on both sides so it was running level.
- Then generally I left the drive trimmed where it was (unless I came off plane), and used the tabs to level the boat or drop the bow if needed.

But every boat is different and reacts differently. Yours is a bit larger, so you may need more tabs and less drive trim.

I generally found that forcing the bow down with I/O trim made the handling too squirrely so only did that when getting on plane. Once on plane, everything is done with the trim tabs.
 
So, generally speaking ... is the Sundancer hull most efficient when on plane with the bow as far down as possible ... or is it more efficient with the bow higher?

Thanks everyone ...
 
I'd say running flat to slightly nose high, but your GPS is your friend to find that with your boat based on engine trim, trim tabs, load, conditions., etc.,...

When I get on plane and set the engines then it's a process to make sure everything is optimized. I pull the tabs all the way up and usually the nose goes up a little and the speed goes down. I trim the tabs down until I've got the best speed. Engine trim is part of this too. Doing it all at once is kind of like a complex ballet!
 
Here is another tip for optimum drive trim. When get on plane with drive down you will see a spray coming off both sides of the drive at a 45 angle.
Trim up about a 3 count until the spray goes away. Now you at at about the optimum trim for the drive.
 
As you trim, watch your RPMs. If your RPMs climb you are reducing drag which is a good thing. A nose down attitude is good if you are going into a chop where comfort may be an overriding consideration to fuel efficiency. Generally speaking you strive for the best speed at the lowest rpms while not exceeding 75% of your rated WOT. It is generally more comfortable to ride a little bow down into a chop and a little bow high if the waves are coming from behind. Also, go easy on the hull so you are not pounding which is hard on the structures. Don’t obsess over speed. Run the boat with the right trim and speed consistent with a comfortable safe ride.
 
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