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    Power Trim and Trim Tabs

    So I have just gone down what seems to be a rabbit hole by trying to figure out the best way to use these in conjunction by watching you tube videos and reading online articles and figured what better way than to see how others use theirs. So I am new to boating with a fast boat that can plane, and I was under the impression that the boat will run fastest and most efficiently with the least amount of hull in contact with the water. So as I run I pull my trim tabs up after getting on plane, most of the time I don't need them to get onto plane and just adjust my power trim out to pull my hull out of the water a bit more. Now I have been reading and come across that a properly trimmed boat is keeping more hull in the water with the tabs and adjusting the engine trim, of course it's 1 o clock in the morning now so I can't go test it out. I run a 2003 245 with a 350MPI Repower and I usually cruise at around 26-28MPH at 3200rpm and 42mph at 4800rpm. I don't know if these speeds are slow for their rpm and if proper trimming could get me going faster. Have I been destroying my engine by overworking it poorly trimmed? I'd love to hear how others use their trim tabs and engine trim and the results they have found and what is considered the correct planing attitude?

    #2
    I use drive trim for adjusting the hulls "attitude" in the water and use tab trim to adjust list mostly. Basically less trim tab = less drag but some larger more stern heavy boats will benefit from more aggressive trim tab to create additional lift in the ass end. I don't imagine your 245 being to ass end heavy.
    Your speed/rpm numbers sound great IMO.
    BTW don't run at WOT! It's just a test range to verify correct prop pitch etc.
    Dave
    Edmonds, WA
    "THE FIX"
    '93 2556 5.7 Bravo II 2.0:1 18 1/4x19 P
    (.030 over-Vortec top end-part closed cooled)
    The rebuild of my 2556 https://www.baylinerownersclub.org/f...76?view=thread
    Misc. projects thread
    https://www.baylinerownersclub.org/f...56-gctid789773

    Comment


      #3
      Never WOT? not even for like 10 minutes? 5 minutes? 15 minutes?

      Comment


        #4
        Personally I run WOT almost every time I go out, for about 20-30 seconds. The rest of the time my cruise rpm is somewhere between 3400-3800
        Dave
        Edmonds, WA
        "THE FIX"
        '93 2556 5.7 Bravo II 2.0:1 18 1/4x19 P
        (.030 over-Vortec top end-part closed cooled)
        The rebuild of my 2556 https://www.baylinerownersclub.org/f...76?view=thread
        Misc. projects thread
        https://www.baylinerownersclub.org/f...56-gctid789773

        Comment


          #5
          I use the trim tabs to get on plane quicker at lower speed. Once on plane, I back off on the trim tabs as much as i can. Tabs do allow me to stay on plane at lower speeds. I rarely run above 3600 rpm for more than a minute or two. With the 5.0 and a 19 pitch prop 3600 rpm delivers +/- 23 kts.
          Dale & Lucy
          I grew up on Lake Superior in MI and Lucy near the coast of CT. Love the water.
          We are in the Wilmington NC area and almost all our boating is on the ICW.
          Bought our first boat, a Glastron 175 SX in 2013. We quickly got tired of being rocked by the bigger boat wakes.
          Started to look for the new and bigger boat in 2014 and found our 2007 Bayliner 245 SB in 2015. "One Moore Time" Merc 5.0 carb model w/ Alpha 1 Gen 2.
          We keep her in drystack at Southport Marina.
          She handles the water and wakes much better and is still trailerable.
          We mostly do day and sunset cruises with some overnight and weekend trips

          Comment


            #6
            different people use different procedures in the quest for a perfect trim.... and it all comes down to how easily you can get the boat to move thru the water.

            I start with my drive all the way down, and after getting on plane I use my tabs to get the highest speed and lowest fuel consumption (on the floscan meter)... and then i adjust the drive up a little, which does make a difference, and then fine tune the tabs and the drive until everything is running at its easiest..... after one gets used to where the sweet spot is in their boat, it can generally be trimmed fairly quickly.

            the "perfect" setting always changes with a change in speed or weight movement within the boat, AND with a change in water surface conditions, so one can always be searching for perfect, which can become too much like work, so we just find a happy medium and go with it until there is a drastic change that warrents another search for the perfect trim....

            efficiency at any given speed is limited by the power, weight and hull design
            its true that the less hull is in the water, the less drag there will be, but if getting the maximum amount of fiberglass out of the water by adjusting the trim for the most lift is taking all the power with little left to propel you forward, its counterproductive.... there is a balance that needs to be found with the power that you have available, and the displacement weight and design of the hull.

            as for rpm, first, the prop must be sized to allow the correct recommended rpm for the engine... after this, the actual engine rpm is less critical. (if the prop is not correct, the efficiency potential will never be met, and the engine rpm will be wrong, and engine rpm due to a mismatched prop can be VERY critical to the longevity of the engine)...

            the manufactures have recommended an rpm range that they feel comfortable with so they dont have unreasonable warranty issues, yet allow for a decent power/speed.... exceeding the recommendations WILL shorten the engine life, just as running it much easier can lengthen the expected engine life.... but its not written in stone that there is going to be an immediate failure if one were to exceed 6000 rpm for an hour or two. but neither is it recommended by the manufacture... AND with the marine cam that is used in the engine, it becomes less efficient as the rpms climb above the recommended rpm, so there is little point.....
            a camshaft is ground for a particular RPM range, and the OEM cam that the engine is built with offers the best rpm range for our types of boats and usage..

            I have always used the full rpm range to its limit whenever I felt like it, without a failure or other noticeable problems, so I would never tell anyone they shouldnt run at WOT, but I will only say the manufacture recommends against it....
            due to fuel costs and the desire to enjoy the boating experience without stressing myself or the boat too much, i seldom feel the need to run at sustained (over 20 mins) WOT any more (but sometimes it still happens).. but then, I intimately know the risks of doing so and fully accept whatever happens because of my decisions...

            Ive spent a few years working and playing on the ocean, and the most stress that is ever placed on a well maintained UNGOVERNED engine is when crossing the bar in rough weather where at one moment you may be over rev'ing the engine as you surf down the face of a swell, and for the next minute or two you are WOT and lugging the engine to attempt to keep pace on the back of the swells and breaking waves... and even though this is extremely harmful to the engine, the manufacture does not recommend against running the engine in any manner that it has to be ran in order to keep control of the boat...... if one were to continuously run the boat this way for hours upon hours everyday, the engine would definitely not last 40 years like some do, and probably not even 5 years...... (and I would like to offer the warning that surfing/racing down the back side of a wave comes with a severe danger of broaching, so dont do it)

            with a boat, no matter how you use it, how you run it, how you load it, how far or where you go with it, if you do it in a CONSERVATIVE manner you will be happier and the boat (and you) can last a long time without breaking... the only place for an AGGRESSIVE attitude in boating is when it comes to the maintenance program...
            Last edited by Centerline2; 09-09-2018, 07:41 PM.


            NU LIBERTE'
            Salem, OR

            1989 Bayliner 2556 Convertible
            5.7 OMC Cobra - 15.5x11 prop
            N2K equipped throughout..
            2014 Ram 3500 crew cab, 6.7 Cummins
            2007 M-3705 SLC weekend warrior, 5th wheel
            '04 Polaris Sportsman 700 -- '05 Polaris Sportsman 500 HO
            Heavy Equipment Repair and Specialty Welding

            Comment


              #7
              Thanks for all the info, being new to boating it is a valuable resource to have all your input! Sounds like I should also get a flow meter to be able to monitor the efficiency of the trim setting!

              Comment


                #8
                Originally posted by Keelay View Post
                So I have just gone down what seems to be a rabbit hole by trying to figure out the best way to use these in conjunction by watching you tube videos and reading online articles and figured what better way than to see how others use theirs. So I am new to boating with a fast boat that can plane, and I was under the impression that the boat will run fastest and most efficiently with the least amount of hull in contact with the water. So as I run I pull my trim tabs up after getting on plane, most of the time I don't need them to get onto plane and just adjust my power trim out to pull my hull out of the water a bit more. Now I have been reading and come across that a properly trimmed boat is keeping more hull in the water with the tabs and adjusting the engine trim, of course it's 1 o clock in the morning now so I can't go test it out. I run a 2003 245 with a 350MPI Repower and I usually cruise at around 26-28MPH at 3200rpm and 42mph at 4800rpm. I don't know if these speeds are slow for their rpm and if proper trimming could get me going faster. Have I been destroying my engine by overworking it poorly trimmed? I'd love to hear how others use their trim tabs and engine trim and the results they have found and what is considered the correct planing attitude?
                Hi Keelay,

                I also have a 2003 245, but I have a 357 4v alpha repower. I find that the boat wanders a lot when running in displacement, and that putting the trim tabs full down helps a lot to minimize this issue. I also have a hard time getting up on plane when fully loaded, 2 adults, 2 kids, full fuel, and water, Honda 2000 generator, cooler etc. Putting the trim tabs fully down helps me get up on plane quicker in these conditions, still takes a good 20 seconds though. Once up on plane I remove the trim as much as possible, to reduce drag. and then trim up the sterndrive as much as possible, without porpoising. The idea as I understand it is to get as much of the boat out of the water as possible to minimize drag, but to be in a stable situation. I am also a new boater though, so don't take my word for it.

                Just out of curiosity what prop are you running? I had a 15x17 originally, but I found the WOT RPM's were to high, 5200, so I swapped to a 14.5x21 which brought my WOT RPMs down to about 4400. You stated that you cruise about 28 mph, but I find that I can't stay on plane much under 30. How long does it take you to get up on plane? I'm not sure what my WOT speed is but I don't think its much more than 35. Of course I'm going by the Speedometer, I really need to check it with a gps.

                Comment


                • Keelay
                  Keelay commented
                  Editing a comment
                  Hey Jakwi,
                  I think I run a 14.75x16 SS Enertia prop(it's a 16 pitch not positive the diameter). I had a 19 but it left my rpm way to low, but with the 16 I get 4800RPM at WOT. With just me and my gf and my 2 Boston terriers it's about 6-10(timed just over 5 seconds after prop change but since added more weight into the boat) seconds to plane with tabs fully up but no generator and any weight I have I try and load in the bow it really helps to weigh it down. What you do once on plane is what I do, except I drop off plane around 22mph with no tabs deployed. Have you thought of a 4 blade prop? Maybe prop down a bit to get your rpm closer to mid range than the low range. I hear the 4 blades get you on plane quicker but slow top end and do you have an aluminum or SS? SS has less flex and should help you get on plane quicker as well I believe, I am new and all this knowledge is from YouTube or boat websites lol

                #9
                Originally posted by Jakwi View Post

                Hi Keelay,

                I also have a 2003 245,
                I find that the boat wanders a lot when running in displacement, and that putting the trim tabs full down helps a lot to minimize this issue.
                I also have a hard time getting up on plane when fully loaded, 2 adults, 2 kids, full fuel, and water, Honda 2000 generator, cooler etc. Putting the trim tabs fully down helps me get up on plane quicker in these conditions, still takes a good 20 seconds though. Once up on plane I remove the trim as much as possible, to reduce drag. and then trim up the sterndrive as much as possible, without porpoising. The idea as I understand it is to get as much of the boat out of the water as possible to minimize drag, but to be in a stable situation. I am also a new boater though, so don't take my word for it.

                Just out of curiosity what prop are you running? I had a 15x17 originally, but I found the WOT RPM's were to high, 5200, so I swapped to a 14.5x21 which brought my WOT RPMs down to about 4400. You stated that you cruise about 28 mph, but I find that I can't stay on plane much under 30. How long does it take you to get up on plane? I'm not sure what my WOT speed is but I don't think its much more than 35. Of course I'm going by the Speedometer, I really need to check it with a gps.
                yes, putting the tabs full down with the outdrive full down helps a lot with the low speed wandering...

                running the tabs full down during the hole shot may be a bit counter productive, as it can force the bow down too much to allow the speed to come up as fast as it could..

                BUT, if you are having a hard time getting on plane and you do NEED to run full tabs to do it, and being unable to STAY on plane below 20 mph, indicates the boat is much too heavy in the stern.... it wants to run deep... in this condition there are only two ways to keep it on plane, one is speed (as you have figured) and the other is a weight shift to remove some weight from the rear to the front so the boat attitude is much more balanced.... when the boat is balanced, you should be able to get on plane easier and stay on plane down to at least 15-17mph....

                the prop selection is more critical when the boat is heavy... a prop that wont allow the full recommended rpm range to be achieved is laboring the engine and thru that process potential power is being lost...

                when the FULL recommended rpm can be made, this means the power curve potential is being met so the engine is not laboring excessively, AND with the 2-300 rpm more, the full speed potential is being made....

                a boat that is over propped is less efficient because the engine is being asked to do something it cant, and so is burning more fuel while its attempting to do it. both power and speed are being lost.
                and depending on how severe the load, at some point the engine will just give up (the potential power/speed is being converted to heat in the cylinders so there can be a piston/valve melt down)

                a boat that is under propped is getting its full power potential but may be lacking in speed, which is much better than being over propped as long as the engine is not pushed to far past its recommended max rpm..

                a boat that is commonly (or always) loaded heavy can best utilize a prop that will allow about 100-150 rpm over the recommended max, as this allows enough pitch to get up on plane quickly, and allows for a bit more power when running in heavy swells or pulling water toys....

                like the boat itself, an engine needs to have a balanced load... too much load and its damaging, and at a high rpm, too little load is damaging... and of course, and extremely high rpm indicates too little load...

                by design and testing, engine potential is measured by heat build up within the engine and the torque and hp it can create at a given rpm and load without self destructing, and run dependably there for many many hours.... when the load on the engine is shifted outside of its recommended parameters, the engine life hours can decrease significantly...

                bottom line is, opposed to the engine potential itself, the potential of any given design of hull/boat, is determined by the tuning of the engine, the tuning of the propeller, and the tuning of the balance within the boat. when these 3 things are right, the boat will be tuned to its full potential...




                NU LIBERTE'
                Salem, OR

                1989 Bayliner 2556 Convertible
                5.7 OMC Cobra - 15.5x11 prop
                N2K equipped throughout..
                2014 Ram 3500 crew cab, 6.7 Cummins
                2007 M-3705 SLC weekend warrior, 5th wheel
                '04 Polaris Sportsman 700 -- '05 Polaris Sportsman 500 HO
                Heavy Equipment Repair and Specialty Welding

                Comment


                  #10
                  Originally posted by Centerline2 View Post

                  running the tabs full down during the hole shot may be a bit counter productive, as it can force the bow down too much to allow the speed to come up as fast as it could..

                  BUT, if you are having a hard time getting on plane and you do NEED to run full tabs to do it, and being unable to STAY on plane below 20 mph, indicates the boat is much too heavy in the stern.... it wants to run deep... in this condition there are only two ways to keep it on plane, one is speed (as you have figured) and the other is a weight shift to remove some weight from the rear to the front so the boat attitude is much more balanced.... when the boat is balanced, you should be able to get on plane easier and stay on plane down to at least 15-17mph....
                  This makes sense, It's not so much that I can't get on plane, but that it seems to take a long time. Putting the tabs down seemed to help, but to be honest I haven't done a timed comparison. so almost everything I'm relating it anecdotal.

                  Originally posted by Centerline2 View Post

                  the prop selection is more critical when the boat is heavy... a prop that wont allow the full recommended rpm range to be achieved is laboring the engine and thru that process potential power is being lost...

                  when the FULL recommended rpm can be made, this means the power curve potential is being met so the engine is not laboring excessively, AND with the 2-300 rpm more, the full speed potential is being made....

                  ...

                  a boat that is commonly (or always) loaded heavy can best utilize a prop that will allow about 100-150 rpm over the recommended max, as this allows enough pitch to get up on plane quickly, and allows for a bit more power when running in heavy swells or pulling water toys....
                  I went from a 15x17 (5200 rpm at wot) to a 14.25x21 (4400 rpm at wot) mostly because I found one on Craigslist for $30, not perfect as you might imagine, but until I get it narrowed down it seemed like a cheap way to test. I'd like to try a 14.5 x19, which should put my WOT at 4800, right where it should be per the engine manufacturer. Even so with the 14.5x21 I find that once I'm up on plane it will still wind up to about 5000 if I don't back it off, I assume this has more to do with hull design than anything else. The other thing that I haven't mentioned is that my trim tabs didn't work when I was running the 15x17 prop, but if I read your reply correctly it seems like I shouldn't really be using them to get up on plane.

                  Just to be clear that I understand when you say overpropped you mean to much pitch, versus under propped being to little?

                  I'm understand what you're saying about it being a balance of power, gearing and weight/distribution, but it does seem that the weight distribution issue is by design. Water/blackwater tanks, fuel tank, and motor are all in the rear, and without baffles, so all the weight goes to the back when trying to get up on plane. By comparison the lighter stuff, luggage, cushions, and possibly people sit in the front. moving a few hundred pounds(people) to the front can have a huge impact, so why didn't they put some of the designed weight further forward. and realistically what can you do besides asking everyone to move up front?

                  The prop seems like the only variable that is easily corrected. I'm hoping to find out what other 245 owners are running just to see what direction I should go in. Anyway thanks for replying to my post and sorry for hijacking the thread.






                  Comment


                    #11
                    Originally posted by Jakwi View Post





                    I went from a 15x17 (5200 rpm at wot) to a 14.25x21 (4400 rpm at wot) mostly because I found one on Craigslist for $30, not perfect as you might imagine, but until I get it narrowed down it seemed like a cheap way to test. I'd like to try a 14.5 x19, which should put my WOT at 4800, right where it should be per the engine manufacturer. Even so with the 14.5x21 I find that once I'm up on plane it will still wind up to about 5000 if I don't back it off, I assume this has more to do with hull design than anything else. The other thing that I haven't mentioned is that my trim tabs didn't work when I was running the 15x17 prop, but if I read your reply correctly it seems like I shouldn't really be using them to get up on plane.


                    Just to be clear that I understand when you say overpropped you mean to much pitch, versus under propped being to little?

                    I understand what you're saying about it being a balance of power, gearing and weight/distribution, but it does seem that the weight distribution issue is by design. Water/blackwater tanks, fuel tank, and motor are all in the rear, and without baffles, so all the weight goes to the back when trying to get up on plane. By comparison the lighter stuff, luggage, cushions, and possibly people sit in the front. moving a few hundred pounds(people) to the front can have a huge impact, so why didn't they put some of the designed weight further forward. and realistically what can you do besides asking everyone to move up front?
                    ,
                    I was to understand from your previous reply that after changing the prop to the 21p, that it brought your WOT rpm down to 4400.... this is a bit too low for the best performance, but then you say that it will still make 5000rpm with the 21p?
                    the WOT rpm should be checked on calm water on a windless day. the max rpm that you are able to make should be 4800 when the throttle is wide open at a sustained speed... if it climbs to 5000, it may still be under propped a bit, BUT, check and see if the 21p prop has cup on the trailing edges of the blades... if it has no cup, a prop shop could hammer some in. which would bring the WOT rpm down 100-150 rpm...

                    over propped is too much pitch or too much blade, and under propped is the opposite... all things equal, the larger diameter the prop is, the more efficient it will be, but the actual square inches of the blade has more to do with slip at a given rpm of the prop... some slip is necessary. but too much is not desirable, and props can be selected with different blade sizes to meet the individual requirements of the boat and its usage..



                    NU LIBERTE'
                    Salem, OR

                    1989 Bayliner 2556 Convertible
                    5.7 OMC Cobra - 15.5x11 prop
                    N2K equipped throughout..
                    2014 Ram 3500 crew cab, 6.7 Cummins
                    2007 M-3705 SLC weekend warrior, 5th wheel
                    '04 Polaris Sportsman 700 -- '05 Polaris Sportsman 500 HO
                    Heavy Equipment Repair and Specialty Welding

                    Comment


                      #12
                      Originally posted by Centerline2 View Post
                      ,
                      I was to understand from your previous reply that after changing the prop to the 21p, that it brought your WOT rpm down to 4400.... this is a bit too low for the best performance, but then you say that it will still make 5000rpm with the 21p?
                      So from a stop WOT RPM 4400 once it gets up on plane and starts gathering speed it will gradually climb to about 5000 with the 21p prop if I don't back it off. The prop is a Quicksilver Black Diamond 3 blade RH prop.I really don't know what the top speed is as the RPM seemed to high to leave it there.

                      Originally posted by Centerline2 View Post

                      the WOT rpm should be checked on calm water on a windless day. the max rpm that you are able to make should be 4800 when the throttle is wide open at a sustained speed... if it climbs to 5000, it may still be under propped a bit, BUT, check and see if the 21p prop has cup on the trailing edges of the blades... if it has no cup, a prop shop could hammer some in. which would bring the WOT rpm down 100-150 rpm...

                      over propped is too much pitch or too much blade, and under propped is the opposite... all things equal, the larger diameter the prop is, the more efficient it will be, but the actual square inches of the blade has more to do with slip at a given rpm of the prop... some slip is necessary. but too much is not desirable, and props can be selected with different blade sizes to meet the individual requirements of the boat and its usage..
                      So from what I understand from what you are saying I am still underpropped? I'll have to look at the cup



                      Comment


                        #13
                        Jakwi, WOT testing happens after your up on plane trimmed to achieve the best speed etc. You could probably try a larger diameter prop.
                        Dave
                        Edmonds, WA
                        "THE FIX"
                        '93 2556 5.7 Bravo II 2.0:1 18 1/4x19 P
                        (.030 over-Vortec top end-part closed cooled)
                        The rebuild of my 2556 https://www.baylinerownersclub.org/f...76?view=thread
                        Misc. projects thread
                        https://www.baylinerownersclub.org/f...56-gctid789773

                        Comment


                        • Centerline2
                          Centerline2 commented
                          Editing a comment
                          I agree... the 14.25 diameter may be allowing too much slip, which is probably why the rpm continues to slowly climb...

                        #14
                        Are you near Vancouver BC? I have a 19 pitch SS Enertia you could try and see where it gets you at WOT

                        Comment


                          #15
                          Originally posted by builderdude View Post
                          Jakwi, WOT testing happens after your up on plane trimmed to achieve the best speed etc. You could probably try a larger diameter prop.
                          I found a 14.8x19 Brand new Solas Aluminum 3 blade prop for $60 on Craigslist, it has the older style fixed hub though, so I don't know if that's a good deal or not.

                          Originally posted by Keelay View Post
                          Are you near Vancouver BC? I have a 19 pitch SS Enertia you could try and see where it gets you at WOT
                          Hey I appreciate that, but I'm in Florida, near Daytona Beach. To far to swing up there I think (hey sorry for hijacking your thread!)

                          Comment

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