280DA how to set the best throttle,drive trim and trim tab

[melida]

Last saturday I filled fully the fuel tank and then went for a short ride only me without any acceleration problem.

On sunday me and my buddy (both of us weigh 200+kg) full diesel, full water and water heater, campers on and provisions for two people. Weather was sunny 22C degrees and sea was as flat as glass.

Boat got up on plane perfectly. Reached 3000 rpm and did 19 knots. On the way back home we were upwind but the wind was barely swinging the flag.

To test my boat's performance before haul out that was a perfect sea/wind condition. Did fast cruise at 3500rpm and got 25-27knots and did wot but got 3700-3800 instead of 3900-4000rpm due to 3 weeks before cleaned hull/leg/gear fouled again.

To maintain the cruising/planning on the way back home I had to do 3100rpm, fully retracted trim tabs and +1+2 degree drive trim OR 3000rpm, 1/4 1/2 trim tabs and 0 degree drive trim.

IMO doing 3100rpm felt me better than the 3000rpm because the sound of engine/hull and rooster tail was flat and away from stern as a clean hull. But When I did 3000rpm and before applying tabs and keeping leg at 0 degree, a little bow high like need to hit throttle a bit more and rooster tail was in the mid of stern and it's place where to be normally.

Doing two scenarios gave me the same speed but I preffered the 3100Rpm and respective tab/leg settings.

Here comes the magic question.

Which case of scenario gives me the best/better fuel economy while hull/gear is fouled or clean but loaded since I don't have a onboard computer or fuel flow meter.

I know that less drag (properly trimmed hull) but high rpm should be the better.

Let me know what other (especially 280DA owners) members thinks and suggest.

Thanks in advance.

 

[melida]

Ooopss
Is this thread banned ?

 

[Lazy Daze]

No, not banned :grin:

You have a popular boat, but it has a diesel in it - so that's a bit of an oddball (not a bad thing) setup for most on this board. Even the drive settings you posted are unfamiliar to most (including me) as those numbers may not correlate to the same thing on a Mercruiser.

To answer your question another way... "Typically" speaking, most planing-type boats run most efficiently with their bow just a few degrees high. One way to judge (estimate) this is where the "spray" (off the side of the hull) is. If it's spraying out about 2/3 of the way aft, you're doing pretty good. This usually means the drive is tilted up a bit - then use the tabs a bit to control the bow, if need be.

You mentioned how the boat "felt" to you. With experience, that is a very good way to properly trim the boat. The boat should feel "lighter" and "smoother". Ultimately, the best way for you to know is to experiment (as you are doing). Try to run at least 40-50 gallons a certain way and then fill up and divide by the number of hours on your clock since the last fill up (the more gallons you can run through, the more accurate your numbers will be). Then try something else.

That's the "basics", but maybe some other 280 owners can at least help with where the the spray is coming off their boat at, what they found, is the most efficient running attitude. That (the spray) would probably be the best thing to compare from hull to hull, since the power package is different.

Obviously, conditions of the sea can have a dramatic effect on where the "ideal" running position is.

 

[melida]

No, not banned :grin:

You have a popular boat, but it has a diesel in it - so that's a bit of an oddball (not a bad thing) setup for most on this board. Even the drive settings you posted are unfamiliar to most (including me) as those numbers may not correlate to the same thing on a Mercruiser.

To answer your question another way... "Typically" speaking, most planing-type boats run most efficiently with their bow just a few degrees high. One way to judge (estimate) this is where the "spray" (off the side of the hull) is. If it's spraying out about 2/3 of the way aft, you're doing pretty good. This usually means the drive is tilted up a bit - then use the tabs a bit to control the bow, if need be.

You mentioned how the boat "felt" to you. With experience, that is a very good way to properly trim the boat. The boat should feel "lighter" and "smoother". Ultimately, the best way for you to know is to experiment (as you are doing). Try to run at least 40-50 gallons a certain way and then fill up and divide by the number of hours on your clock since the last fill up (the more gallons you can run through, the more accurate your numbers will be). Then try something else.

That's the "basics", but maybe some other 280 owners can at least help with where the the spray is coming off their boat at, what they found, is the most efficient running attitude. That (the spray) would probably be the best thing to compare from hull to hull, since the power package is different.

Obviously, conditions of the sea can have a dramatic effect on where the "ideal" running position is.

Dennis,
Great thanks for your detailed explanations.
You made me self confident of my boat's running attitude.
After two years of ownership my boat (and boating year round) I've just felt myself domineering the boat with the different sea, wind and load conditions.
Thanks again.

 

[Presentation]

Melinda,

Dennis is correct. We have the same boat at the core but the setup is different.

I’d be telling you what works for my boat, not yours.

Best wishes Melinda.

 

[melida]

Melinda,

Dennis is correct. We have the same boat at the core but the setup is different.

I’d be telling you what works for my boat, not yours.

Best wishes Melinda.

Thanks Pres.
Awaiting curiously.
Tomorrow is a feast and I'm off work. Ofcourse gonna boating and try what you'll tell.

 

[Tonka Boater]

Melida,

My numbers for a comfortable and efficient cruise speed are pretty close to yours -- 3100 rpm and +2 drive trim (maybe a little more, I trim it up 1/4). This feels way more comfortable than using the tabs and it "feels" more efficient. I can't back up the efficiency but it just feels good. I have a smooth wake and minimal spray off the sides.

 

[melida]

Melida,

My numbers for a comfortable and efficient cruise speed are pretty close to yours -- 3100 rpm and +2 drive trim (maybe a little more, I trim it up 1/4). This feels way more comfortable than using the tabs and it "feels" more efficient. I can't back up the efficiency but it just feels good. I have a smooth wake and minimal spray off the sides.

Tonka,
Thanks for your reply.
But I think you forget that my engine is diesel which is black and white with your engine.:grin:
What I can tell is Mercruiser's fully drive down is 0 degree and mine is -9.
To get up on plane I have to fully deploy my (enlarged) trim tabs and fully drive down. Then once on plane first I bring my drive to 0 degree. Don't know exactly how much cm/inches drive travels/raises from -9 to 0 but it lifts the boat up. Then I fully retract trim tabs and that lifts up the boat too. While that drive trim and tab settings the spray is just under the helm seat level. Acording to sea and load conditions also I raise the drive to +2, also at fast cruise(3500rpm) and at wot I raise the drive to +5 which is the limit before beach range.
Up to know I thing I learned my lesson well.
The confusing part is (as I mentioned in my first post) when the conditions are bad.

 

[Lazy Daze]

Melida - "bad weather" and "efficiency" don't play nicely with each other. Typically, speaking, you're going to want to plant the bow a little firmer so you can use the high deadrise angle at the bow to slice through the waves. Your bow has a very steep angle to it, the stern is nowhere near as steep. To do this, you need to increase the use of tabs and/or adjust the drive trim angle. There's no "one" correct answer for how to do this, but I prefer to keep the drive trimmed so the thrust is about parallel with the keel and then use the tabs to correct from there. If the drive angle is much higher or lower than the keel, some efficiency gets lost as the propulsive thrust is not directly in line with the hull (some thrust/energy is lost to lifting or pushing down the stern). Of course, this is not an exact science and some hulls can be designed differently and this idea may not hold as true in some cases.

If you feel like getting in the water, you can correlate actual drive position to your gauge. Take a straight edge and hold it against the hull bottom. Allow it to stick aft enough so you can line up the anti-ventilation plate (flat plate directly above your props) to the straight edge. Once the plate is parallel to the hull bottom, look at your gauge and see what it reads. Start with that position as your most efficient running position... use tabs to fine tune... adjust drive trim as needed from there. You may or may not find, with trial and error, that is the most efficient position.

 

[melida]

Melida - "bad weather" and "efficiency" don't play nicely with each other. Typically, speaking, you're going to want to plant the bow a little firmer so you can use the high deadrise angle at the bow to slice through the waves. Your bow has a very steep angle to it, the stern is nowhere near as steep. To do this, you need to increase the use of tabs and/or adjust the drive trim angle. There's no "one" correct answer for how to do this, but I prefer to keep the drive trimmed so the thrust is about parallel with the keel and then use the tabs to correct from there. If the drive angle is much higher or lower than the keel, some efficiency gets lost as the propulsive thrust is not directly in line with the hull (some thrust/energy is lost to lifting or pushing down the stern). Of course, this is not an exact science and some hulls can be designed differently and this idea may not hold as true in some cases.

If you feel like getting in the water, you can correlate actual drive position to your gauge. Take a straight edge and hold it against the hull bottom. Allow it to stick aft enough so you can line up the anti-ventilation plate (flat plate directly above your props) to the straight edge. Once the plate is parallel to the hull bottom, look at your gauge and see what it reads. Start with that position as your most efficient running position... use tabs to fine tune... adjust drive trim as needed from there. You may or may not find, with trial and error, that is the most efficient position.

Dennis,
Great thanks again for the detailed info.
As you mentioned I'm always trying to benefit from the sharp bow when bad weather.
About the calculation of the drive angle, could it be in the water or out of water? I guess in water must be the correct calculation since the boat has the actual sitting position in the water.
For fine tuning I don't use my tabs for two reasons.
First is since I have enlarged tabs, tabs are doing their job for lowering the bow more than balancing. When I deploy them full or a few they balance the boat but also lowers the bow which is not a good thing on plane IMO.
Second is even the sitting is at the port side and/or side winds/waves I don't use the tabs to level the boat while listed, because I have autopilot and 99%of time on plane I use it and autopilot corrects the listing by steering. Also it is recommended that when autopilot is activated tabs should be fully retracted (except urgent circumstances) to keep a straight course and for not fooling the autopilot.
If the weather permits I'm gonna try tomorrow both you and Pres suggested and gonna took photos of wher the boat kisses the water(spray) and also pics of tabs and leg position.
Thanks again.

 

[Lazy Daze]

Doing it in or out of the water won't matter - it's simply a relation between hull and drive. Again, though, this is just a starting point and the actual drive position (for best efficiency) is dependent not only on hull design, but also sea conditions.

 

[melida]

Doing it in or out of the water won't matter - it's simply a relation between hull and drive. Again, though, this is just a starting point and the actual drive position (for best efficiency) is dependent not only on hull design, but also sea conditions.

Photos from last week when she was on annual maintenance.Don't get angry to me for the wood stuff, unfortunately it's that way in my country where I'm in the best marina of my country (they own 7-8)The drive is in the fully down position and you can see the angle where the cavitation plate is not parallel to the hull. Will see in water if its same.
http://i998.photobucket.com/albums/af108/melida315/2001%20maintenance/DSC06323.jpg
http://i998.photobucket.com/albums/af108/melida315/2001 maintenance/DSC06321.jpg
http://i998.photobucket.com/albums/af108/melida315/2001 maintenance/DSC06329.jpg

 

[Lazy Daze]

Will see in water if its same.

The relationship between plate and hull will not change. It won't matter if your boat is upside down or sitting with the nose straight up in the air. I think I'm just not able to communicate this well enough because of the language barrier.

 

[melida]

Will see in water if its same.
QUOTE]
I wanted to tell if the drive position in the pic (boat out of water) is will be in same position when the boat is in the sea. When I'll dive take a underwater pic of it.

 

[Lazy Daze]

I bet it's awful close. If you look at your signature picture and compare it to the the third picture in your post, the boot stripe looks to be at about the same angle.

 

[melida]

Ok then this will be a try and see thing.
Tomorrow gonna try some different throttle leg and tab positions to settle the boat in best level.
PM sent.

 

[melida]

Hi again.

Today was a perfect day for boating and also testing the boat.

I shooted this video while on plane at 3000 rpm, 19 knots, trim tabs fully retracted and drive trim at +2.

Boat was touching the water (I guess thats called the bow spray) just the level of where you put your foot while seating at the helm chair. At the outside of boat it is touching where the cockpit drain and sump box drain.

I have a water resistant case for camera and shooted with it and also shooted the leg under the platform but its not seen and black in the video.

While on plane the leg was out of water until the cavitation plate and exhaust was under it and there were no smell.(One of a reason that I like stern drive which you don't feel the diesel smell like a shaft driven boat):grin:
[video=youtube;xj0qfDhuBuU]http://www.youtube.com/watch?v=xj0qfDhuBuU[/video]

Dennis, Pres. and who ever watching this thread could you comment on the video if its correct or need trimming?

But the boat was running good and engine was not laboring.

Thanks in advance.

 

[Lord Farringdon]

Hi Sayat,

WARNING: LONG POST

Sorry i didn't reply sooner but I have been away on business and haven't had the time to look at the site for a while. I see you have anti-fouled your boat. It always looks so good after it is done that its hard to put it back in the water again :lol:

Interestingly, we have both just completed anti-fouling so it will good to see how our paints hold up in New Zealand and Turkey. It will be interesting to see if we both go back for anti-foul at about the same time.

I note you are trying to compare your before and after speeds to see if the antifoul makes a difference. I didn't do any specific pre antifoul checks but I know the boat was running at about 20 knots at 3200 rpm with campers, two people and full water and diesel. when I took the boat out after antifoul, she was running 21.5 knots but that was only one person. Still, looks like an improvement for me. At WOT of 3900 rpm she reached 27.8 knots. I reckon if the campers were off she'd do 30 kts easily.

As for trim, I found -1 at 3900 rpm gave me the best speed but at 3200 rpm and 21.5 kts I need the leg trimmed all the way down at -5 or -4 otherwise she drops speed.

Let's talk about this for a moment. I note you cruise at 3100 and even 3000 rpm. If I go down to 3100 rpm I will drop speed to about 19 kts and even down to 18 kts if I am running into waves. I am dangerously close to falling off the plane so I dont feel 3100 rpm is a very good speed for me and the boat feels like it is waffling a little like an aircraft about to stall. If I dropped rpm further down to 3000 I would definately fall off the plane. So 3200 rpm at between 20 and 21.5 knots (depending wind and sea conditions and people on board) is my preferred cruising speed.

So, what effect does sternleg trim have? I must confess to not really understanding what is going on here. When I am at wide open throttle I trim the leg up and the boat goes faster but at slower speeds/throttles, I need the leg to stay trimmed down to maintain best boat speed. I always thought this had to do with offering the best thrust line for any given speed but that doesn't make any sense to me. There is a point where the cavitaiion plate is parallel with the keel. I'm not sure what that is but I would say it would be a deep trim of say -4 or -5. I would assume this would give the best thrust for any given rpm directly in line with the keel. If you trim up from there you are changing the thrust line and causing the stern to lower and the bow to raise. That's opposite to what we like to see so how can that improve speed? If anything, in an attempt to get as much of the hull out of the water as possible, we should be trimming the sternleg down in order to get the bow down and raise the stern out of the water.

My guess is that sternleg trimming has more to do with reducing form drag than offering best thrust lines. Form drag is the drag on the boat caused by everything that the engine has to push through the water including the hull, tabs, and sternleg. In an aircraft it is equivalent to the cross section of the fuselage and the wings that cause resistance to forward travel. On a bus or a truck it is their big fronts. You will note trucks often have big aerofoils on their roofs to channel the air up and over their cabs and trailers. This is an attempt to reduce form drag or resistance to the air. The other interesting thing about this is that form drag increases as speed increases. If you put your hand out the window of your car with the palm flat against the airflow you will not notice much doing 20 kph but when you are doing 100 kph you will have a hard time holding your hand out the window against the airstream. Your hand in that case is experiencing form drag the force of which gets greater the faster you go. That's why trucks have aerofoils and buses don't because trucks travel on open roads at speed while buses just run around city streets at slower speeds. Buses are not affected by form drag to the same extent as trucks. Reducing form drag on trucks using aerofoils help reduce fuel costs.

Coming back to our boats, it seems to me the sternleg is a big piece of drag below the water. The force on a fully lowered sternleg at WOT must be tremendous and that would slow the boat down if we didn't do something to reduce the force. That's why raising the leg helps. If you trim it up, you can reduce the amount of leg presenting itself to the waterflow and thereby reduce form drag and increase speed. This can only go so far before the thrust line of the sternleg started to lift the bow and lower the stern into the water with consequent lowering of speed. (not to mention prop cavitation) So in my boat -1 is as high as I can trim the sternleg when at WOT.

At slower speeds, (just on the edge of the plane) form drag is not so much of a problem just like the city bus. However, because of the slower speed and even though my sternleg is trimmed down to -5, my boat is cruising with a bow that is higher and a stern that sits lower in the water. As soon as I try to trim the leg up, the wosening thrust line causes the boat to immediately slow down while the reduced form drag on the stern leg has little affect on speeding the boat up, the result of which is an immediate slow down of boat speed.

And I haven't even started on trim tabs:lol:


Terry

 

[melida]

Terry,
Glad to hear from you again.
I was feeling an orphan myself without a VP diesel guy on this board.:grin:
Oops Bill shouldn’t read this.:smt043

The best scenery of a boat is when it’s done the fresh antifouling and wax/polish job.
This year I antifouled my props with trilux as for the leg which didn’t the props last year and suffered too much from the barnacles cumulated over the props.:smt021

Applying trilux to props made me to gain 1-2 knots at cruising speed (3000rpm). I was doing 18,5-20 knots according to as always sea/weather/load/bottom conditions. Now I can reach 21 knots at same rpm while trim tabs fully retracted and drive trim is between 0 and +2 according to same parameters.

As the owners manual says drive travels between -9 to +42 degrees. Mine is set to -8 and when set to -9 trim limiter goes out of line. But at the planning threshold drive goes to -9 because of the thrust and torque,even I set to -8 but it won’t goes out of line.

I know lots of people around me own VP diesel KAD or D4 D6 engines with DPG and DPH legs have set the drive trim max -5. Also when I bought my boat that was -4 to -5. I’ve serviced the leg and my mech set it to -8-9. There is visually and/or physically no difference to set -5 or -9 but if you set to -9 then -5 is further up. Don’t know the technical difference or benefit/damage to set -5 or -9 which one is better.

Let’s turn to our boats.

What I’m doing for planning is trimming the drive all the way down to -8 and deploying the trim tabs fully. I think almost all members of this board know why I use the tabs for planning due to I want to use C4 prop set to have the ability of using the engine power between 3000 and 3500rpm.

After setting the gear for take off I do a steady throttle opening (like I did in past on my motorbike:grin. When rev comes to 3000 I slightly raise the drive 1 by1 degree from -8-9 to 0. This makes the boat longitudinally balanced like moored/berthed. Meanwhile speed shows at gps minimum 18,5knots and I fully retract the trim tabs which raises the bow very easily high but not makes to loose speed. After a few seconds waiting to settle the boat according to conditions I raise the drive to +1 or +2 to decrease the wetted surface which felt better for boat and fuel economy.

While the planning just completed (reached to 3000rpm) and I raise the drive to 0 when the bottom and gear is clean rev automatically raises to 3050-3100 without touching the throttle lever and then I pull it back to 3000 rpm again for fuel economy and also without loosing speed.

My boat even with the cleanest hull and gear and with only me no water no septic and no campers does not like below 3000 rpm for planning. Also I like to keep it at 3000 rpm if the conditions permit BECAUSE 3000rpm is the minimum available rpm of the maximum torque which gives the best fuel economy and engine labour.

I can do 18,5-20 knots at 3000 rpm and 25-27 knots at 3500 rpm. When I splashed my boat this year two weeks ago weather was bad, blowing 5-7 Bft from north and app. 1 meter wave. I had almost full tank (between full and more than ¾, sucked 30liters of diesel as for cleaning the bottom of tank) full water and app. 25liters septic, also campers on. Guess what she did.

She did 30,5knots with that weight and sea/weather conditions.

A few days later that day with an almost perfect day for boating she reached 32-33 knots with me admiral and daughter onboard, full water, almost same fuel and empty holding tank.

Yesterday I’ve removed the campers and have put the cockpit cover. Also I only (unfortunately) leave the back side bimini top attached to the arch and always roll the front bimini and rear extended bimini/sunshade except moored. I guess without campers and bimini tops assuming clean hull/gear I will see again 35 knots and at 3500 rpm while downstream 28-29knots.

What I do about the power trim/drive/leg setting is very different from yours.

At cruise 3000 rpm leg is at 0 +1 +2. I could even do +3 but since I have the extended tabs they start to touch water from their aftest point (even I did negative angle as David/Dpmulvey suggested) which lead to lower the bow, also +3 does not increase the speed.

At 3500 rpm I set the drive to +5 which is the max permitted trim angle. But my boat needs more trim like +7+8, it should be good because she starts to lower the bow down and makes little jumps (is it called porpoising ?).

My wot is also at 3900 rpm but it can see 4000 rpm which is recommended by most marine technicians to have the props could see +100 +150 rpm than wot. I never do 4000, even 3900 rpm for testing once a month or twice which tells me to the time for diving and cleaning the bottom and gear.:smt021

We have the exact engine and drive and I guess the same raito 1,68:1, but I use C4 prop set and you C2. But the major difference is I have a sundancer and your’s is Amberjack.

Even your boat is smaller and lighter than mine your drive trim is not better then mine.

When on plane after setting to 0+1+2 degree if I lower the drive to -9 the bow is almost droops into the sea, interestingly while you need to do it as you said.

With good running conditions, starting from 3000rpm raising the drive from 0 to +levels increases my boat’s speed 0,5 1 and sometimes 2 knots respectively through 3500rpm.

Up to now I'm happy with my boat and can't wait the weekend for a ride with her.
I'll post some pics soon.

 

[Clasg]

Hi guy's

Have just bought (in june) a 275 Sundancer with a KAD300 diesel engine and DP-G drive.
I have experienced some of the same problems as Melida, regarding very slow acceleration.
The boat weight app. 3.000 kg + fuel, water equiment etc, in total app. 4.100 kg.
Topspeed is 34 knots at 3.600-3.700 rpm (as I remember). Max. rev. are 3.800 rpm for this engine, mentioned in Volvo's manual.
I can get the boat planing by bringing the trimtabs full down and the drive to -5 (which is the lower limit for my engine at the time).
I don't know the propeller size yet, as I haven't been down under yet


I found a thread on this site, where a norwegian guy and his Sundancer 280 experienced some of the same problems, but he solved his problem by changing props to a lower number. Only loss was -2 knots in topspeed.
Melida: Can you tell me, how many seconds it takes for you to reach 20 knots, and topspeed?
And was there a big difference in acceleration, when you used the other set of propellers?