Planing........Gradual or as fast as possible?

[Alex D]

I usually troll out of the marina and side cove at 1200 to 1500 rpm and then drop the tabs 50 to 70% depending on load, roll the throttles smoothly to 3200 rpm under load and keep the engines synced.

Alex, do you have a trim tab gauge? Or are you estimating by the time on the switches.

No I don't ... unfortunately ... what I did is have my wife hit the tab switch while I was swimming and I counted how many seconds it took for the to fully extend and retract the tabs ... abount 12 seconds and it's linear. I add a second for the extension against the water pressure and retraction when running goes also a bit faster, so I subtract a second from this number.

 

[Skip]

Every hull and pwer combination is a bit different, and each is affected by loaded weight, distribution of load within the vessel, current, wind, etc.

For the 420 I never touch my tabs to come on plane. They stay in the bow up position. I only use them to trim port and starboard once on plane, or to lower the bow in really choppy water to soften the passenger's ride if I do not feel like slowing down.

Once the C Series hit 160 degrees I bring the rpms up to 900, engage the glendinning synchronizer, let the engine RPM synch, then I slowly advance the master throttle until I am at cruise RPM--2100 or so. The 420 has almost no bow rise.

As a newbie diesel owner I would advance the throttles more quickly, as I did with my 320, but the Cummins tech recommended a slow roll-on and roll off the throttle to go onto/off of plane. I belive the rationale is to minimize stress on the engines as I come on plane.
The slow decelaration apparently minimizes stress on my comparatively low-tech non-wastegated turbos, but that is probably a whole new thread topic, and is an area that I am not yet sufficiently versed to comment intelligently.

I really, really like the absence of bow rise in the 420 diesel, even with a load of folks in the cockpit. The Potomac and tributaries can get really busy and I appreciate clear lines of sight.

regards
Skip

 

[cr0ck1]

with em i cant really go slow ... it will jsut bring the front end so high its scary.. now my boat is not as big as most if the big guys on the forum.. but i dont punch it either.. i just speed up and when im on the verge of plane i give it alittle more gas than im on and lower the speed... i dont know if this helps but this is what i do.. i never ever punch the throttle.. or i havent yet.

 

[RonF]

what I did is have my wife hit the tab switch while I was swimming and I counted how many seconds it took for the to fully extend and retract the tabs ... abount 12 seconds and it's linear. I add a second for the extension against the water pressure and retraction when running goes also a bit faster, so I subtract a second from this number.

Ah ha.....way to go.

 

[Carpedmman]

Off topic...sort of...I also fully deploy the tabs when coming off plane. I come off the throttles slowly and steadily. With the tabs down, it helps to bring the bow down quicker and minimizes that big surfing wake at the transom caused from squatting.

I do the same as Dominic using the trim and trim tabs during acceleration...but using the tabs during decelleration is something I've never tried and will be interested to try this technique. Thanks Dominic!

Stuart

 

[comsnark]

On a 40 minute run last weekend, I experimented with tab and drive position to optimize GPS speed. Running at 3200 RPM and 34MPH, I was able to vary speed by about 1-2 mph.

And then I came off plane to pass under a bridge, and forgot to reset everything. I pushed the throttles to get back on plane and WHAM! The stern digs in- REALLY DIGS IN - and bow points to the sky! YIKERS!

As I sheepishly back down and correct my mistake. . . . boating is fun!!

 

[Dave M.]

I use tabs much the same as Alex describes. Mine are the same speed as his, so have to be preset in the down position before accelerating. I do have a position indicator on mine; use it a lot. With only me on board and less than a quarter tank of fuel, I can get on plane without tabs, but normally use about 25-50% anyway. With three quarters of a tank of fuel, and just me, I would use 50-75% tabs. And with heavily loaded, then full tabs. In any case, I trim the outdrive down to a bit less than fully down.

I usually go full throttle in a few seconds of roll-up, then back off to keep RPM below 3600 or so. Bow rise is a real issue when I am heavily loaded, and I want to minimize the time I can't see. Accelerating slower only makes it worse. Boat handling is also very poor when plowing, but I never begin to go on plane without a clear route ahead. I want no turns until on plane, and RPM and trim reasonably set.

Also, no engine RPM over 2000 until engine temp is over at least 130, preferably 140.

 

[Dave M.]

Off topic...sort of...I also fully deploy the tabs when coming off plane. I come off the throttles slowly and steadily. With the tabs down, it helps to bring the bow down quicker and minimizes that big surfing wake at the transom caused from squatting.

I've gotta try this. Sounds like a good tip I have not heard before. I usually bring the throttle back to about 2000, and let it settle in. Then when off plane, come on down. It would be nice not to have that wake threatening my exhaust manifolds. :thumbsup:

I think I heard of someone actually shutting down too fast and swamping them, but surely I don't remember any names. :grin:

 

[RjVA]

I guess from pulling alot of water skiers and wakeboarders on my inboard wakeboard boat, I've developed the habit of only watching the tach. My cruise RPM is about 3900, so while brining my 260 on plane, I keep the RPM's in the 3900-4k range. Brings her right up, without dumping the throttles and without going over my efficient cruise RPM

 

[osd9]

Using the "tabs down" technique while coming off plane will help to "minimize", but it will not "eliminate" that following wake. Play a little and you will find what works best for your boat......it's helped me on my 330, 380 and now 410....

Again off topic, but on the 410, because I live in a no wake waterfront development, I have to put one engine in neutral or those diesel just want to make too much wake. It's a real bear to steer a twin engine boat, at low speed, on one throttle. I've been using one tab up, and one down in my canals to help steer the boat straigth. Again, certainly helps, but doesn't eliminate the steering issue...


Skip:

You mention

 

[rondds]

i absolutely NEED tabs deployed to get up in a timely manner. from the flying bridge, visibility is not an issue, but this boat is heavy in the caboose. i count "8 mississippi" on the tab switches, then apply steady smooth pressure on the throttles up to around 3400rpm. once the boat is up and engines are revving closer to 4000rpm ( it's funny to watch the floscans absolutely PINNED while all this is happening ), i'll back down to 3200rpm and then re-trim the running angle based on load and conditions.

coming off plane i retract the tabs as the boat slows. i kinda like the little "push" the boat gets from the wake aft. was also a habit i got into b/c one of my tabs used to have a slight fluid leak only in the "down" position. so i never wanted to forget to retract them.