Boat "bucks" when motor is trimmed up

Discussion in 'Boat Repair Help' started by BKS72, Dec 19, 2007.

  1. BKS72

    BKS72 New Member

    Messages:
    3,361
    State:
    East of KC
    I've got a 1980 Lowe flat-bottom (I mean flat, no modified, nothing, it's like Kansas on the bottom of that hull) that just about bucks me out of the boat if I trim the motor up at all. Motor is a 1980 Evinrude 75 horse. Wondering if it's just the nature of the boat or if there's something I could change on the set up (motor higher or lower, further off the transom, etc) that would help it out. Thanks,

    Branden
     
  2. gilmafam

    gilmafam Well-Known Member

    Messages:
    5,466
    State:
    California
    Where do you keep the fuel tank and battery?.... could put on a "fin" on the motor.... get the wieght up front

    bayrunner ray... (the repub Hillary basher)
     

  3. BKS72

    BKS72 New Member

    Messages:
    3,361
    State:
    East of KC
    Thanks for the info! Already have the fin on it, but yes, the fuel tank and battery are in the back - while I'm reworking it this winter I'll try to distribute the weight a little better.
     
  4. gilmafam

    gilmafam Well-Known Member

    Messages:
    5,466
    State:
    California
    Branden... My first boat... (my dad had two), but my first is a 12 ft semi vee.

    I used it to tow my son and friend with the float tube..... to be able to do that, I moved the battery for the trolling motor under the middle seat, as well as the gas tank..... Even with my buddies and their ski boats, we sometime have to have someone lean up over the front to get the "bow down" go get on a plane.....(not to safe to do it thought)

    When Plumbertom1 was using my 12 footer on the colorado river last may, he put another battery in the boat at the back and with his weight and my battery and gas tank, you should have seen the angle on the boat....

    You've got that "big motor"... your ____ body, and gas and battery at the back...... I even moved the back seat position up 10 inches to a different hole pattern to get more room at the back of the semi-vee....

    Move all that stuff to the front.....

    Bayrunner Ray
     
  5. BKS72

    BKS72 New Member

    Messages:
    3,361
    State:
    East of KC
    Good stuff. I figured the front 13' of the 20' boat was more than enough to balance it out, but you're probably right, me, the motor, battery, a full tank of gas are probably almost 700#, the whole boat is probably only what, 800# for a riveted aluminum jon?
     
  6. Big Dav

    Big Dav New Member

    Messages:
    1,016
    State:
    Southwest
    I had a similar situation a few years ago when I re-did my 17 ft Tracker. I re-powered from a 40 hp to the max 70 hp and added a built in 12 gallon fuel tank, three bank battery charger and three very heavy Optima batteries all in the back compartment. I could not use the trim at all and even with fins it would buck you like crazy. I moved the three batteries and battery charger to the center compartments. That allowed me to use the trim on the boat and balanced the boat out. Solved my bucking problems. I wish I would have had this forum to help me out on that boat. Could have saved me a lot of work in the first place.
    When I first started adding live wells and moving things around in my Lowe 2070 I posted some things about what I intended on doing. I think it was Mark J that suggested having a friend or friends sit toward the front to see how the change in balance would make the boat react. Bags of sand will also work and will let you tell more about where the weight might need to be located to find the "sweet spot". That is if you are thinking about changing the lay out of your boat. I hope this helps.:big_smile:

    Thanks
    David
     
  7. BKS72

    BKS72 New Member

    Messages:
    3,361
    State:
    East of KC
    Changing it from a side console to center console, and replacing the decks. Handn't thought of relocating the batteries or fuel tank (ok, that's not completely true, I thought about a belly fuel tank till I saw what they cost:embarassed:) I may be able to relocate the batteries, I do have a bunch of extra 1/0 welding lead in the garage, I might be able to spare 20' to move the battery up front. Dunno about the fuel tank, I'm guessing she'd draw fuel that far, but it'd be a bad deal if it didn't:sad2: Still, if I move those to things that's 200# and change I've relocated to the front. Hmmmmm, I have a feeling the trim is only going to give me maybe a mile an hour, dunno if it's worth the trouble. Must think.
     
  8. Big Dav

    Big Dav New Member

    Messages:
    1,016
    State:
    Southwest
    Branden,
    Keep in mind if you take 100 pounds worth of batteries from the back and put them in the front. You have both increased the weight up front and lightened the weight int he rear. It may not take moving everything up front to get the desired results.:big_smile: I would give the sand bags a try before I invested a lot of time and money.

    Thanks
    David
     
  9. moriverfish

    moriverfish Member

    Messages:
    228
    State:
    Tennessee
    I got a 2072 Sea Ark and I used to have this same problem. The seats were on the back bench with the console right in front of the bench. Could not trim the motor up without begining to porpouse. If two guys were sitting on the front deck, I could trim it up and really hall a$$. What I did was to move the console up about 30" and put pedestal bases in the floor for new seats. I had to get a new steering cable, but the shift and throttle cables were already long enough. My batteries and fuel tank are still in the rear, but man, this really made her a different boat. I can trim here up decent and there is zero torque on the steering wheel now. All you have to do is swivel your seats around to fish out the back. I also have trim tabs on it, these let her plane really fast.
     
  10. catfishcrazy256

    catfishcrazy256 New Member

    Messages:
    2,648
    State:
    Indiana
    i have had the same problems in the past get some weight towards the front , a jack plate will also help :0a26:
     
  11. Lost-him

    Lost-him New Member

    Messages:
    15
    State:
    Idaho
    I had a similar problem with my boat. I have a 4-stroke suzuki 40hp and it works fine at lower altitudes and has plenty of power, but where I live the elevation is around 3000ft so it cut the hp allot. I moved the gas tank to the front of the boat which really helped although i think i still need a bigger motor.
     
  12. coach

    coach New Member

    Messages:
    1,564
    State:
    Greenville , Ms
    big dav is shoooting out some good advice ................... but to answer ur question about the gas tank up front , i moved both my tanks up to the front on a 16footer ....... i am sitting on them in my avatar,,,,, i just bought good fuel line and ran it down the side of the boat back to the motor .......
     
  13. Bubbakat

    Bubbakat New Member

    Messages:
    4,532
    State:
    McMinnvill
    Do as dave is talking about here and do it one thing at a time and then you will know what worked.
     
  14. BKS72

    BKS72 New Member

    Messages:
    3,361
    State:
    East of KC
    Got my new fuel tank in today (I think I got a deal - 23 gallon Moeller belowdeck plastic tank with sender and all the fittings for $70 incl. shipping) and after reading all the responses on this thread I'm going to put it up front under the casting deck. Cuts down a bit on my storage space, but worth it if it stops the boat from porpoising. Also will make it easier to fill it up:smile2:

    Gas is nominally 6# per gallon. The old tank was 18 gallon, so I'm moving 108# from the very back of the boat and putting approximately 140# in the front (figuring in the increased capacity of the new tank). I think it will help out with the trim issues as well as the overall layout and balance of the boat. :smile2:

    Thanks for all of the responses, I'll let you know if it rides any better when I finally get it back on the water.....:embarassed: