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Trolling Motor Questions.. 12, 24, 36 volt? Thrust Ratings? HELP!!!!

Hey guys,

I never knew that purchasing a trolling motor could be so trying.

So many options, that its a bit mind boggling.

My new boat is a 18' Bay Boat with a 90hp 4 stroke

One thing I know I want is an iPilot. I DO NOT need autodeploy but for the right price, I would consider it.

That's as far as I know.

I understand the battery ratio (12 volt = 1 battery 24 volt = 2 batteries, etc)

What is the advantage of the different voltage rated motors?

Also, the thrust ratings are a bit baffling. If I plan on fishing the river, intercostal, etc.. what thrust rating for this boat is recommended?

If I plan on fishing the inlet when the current is ripping, what thrust rating is adequate considering my boat size?

Thanks for any answers you may offer.

Also, if anyone has a motor they are selling or know of someone who is selling one, that would be great.

Cheers

Eric
PLANE FISH N

Replies

  • jackobeetsjackobeets Posts: 82 Deckhand
    Per Minn Kota:

    You will need 1 battery for every 12 volts in your trolling system. We suggest selecting a trolling motor with at least 2 lbs. of thrust for every 100 lbs. of boat weight when the boat is fully loaded with fuel, people, equipment, etc. These are recommendations only - wind, current and other variables affect the way you control your boat, please take them into account and increase thrust accordingly.

    So - how heavy is your dinghy?
  • Plane Fish nPlane Fish n Posts: 6,439 Admiral
    jackobeets wrote: »
    Per Minn Kota:

    You will need 1 battery for every 12 volts in your trolling system. We suggest selecting a trolling motor with at least 2 lbs. of thrust for every 100 lbs. of boat weight when the boat is fully loaded with fuel, people, equipment, etc. These are recommendations only - wind, current and other variables affect the way you control your boat, please take them into account and increase thrust accordingly.

    So - how heavy is your dinghy?

    Good info. Thanks

    18 ISLAND BAY SPECIFICATIONS

    90 HP
    Approx 24 gals*
    1,250 lbs

    So with Minn Kota's calculations I come up with the following:

    90 HP engine = 370 lbs

    Boat Dry = 1250 lbs

    Fuel = 149 lbs full

    incidentals
    & 3 people = 700 lbs


    Total weight = 2469 lbs divided by 100 = 24.69 times 2 = 49.38 so probably a minimum of 50 lbs of thrust? Sound right?

    Eric
    PLANE FISH N
  • JaxJax Posts: 77 Deckhand
    Go to Master Repair in Stuart and talk to Mike. He will steer you right and install it if you want. 50lbs is not nearly enough.
  • BEACHLAUNCHERBEACHLAUNCHER Posts: 16 Greenhorn
    I have a 55 Minn kota on a 12ft aluminum tracker with a 15 hp suzuki, and it is just adequet! Would like an 70...i think you'd need at least an 80.
    No current or wind mine works great wind and current around structure or an inlet it's game over!...i second talking to Mike at master repair.
    He'll know the ins and outs of battery layout also....on an 18 I don't think you'd wanna go 3 batts.
  • Plane Fish nPlane Fish n Posts: 6,439 Admiral
    Great info guys

    I'm in Tokyo and tried to call Mike this afternoon but couldn't get through. I have his number as 772-220-7777 but not working.

    I'll stop by and speak to him for sure.

    Thanks much

    I figured a minimum of 80 lbs thrust but right now looking at a 112 lb thrust motor.

    Eric
    PLANE FISH N
  • Centropomus spp.Centropomus spp. Posts: 343 Deckhand
    Go with at least a 24 volt.... Basically the 24 volt is much more efficient, can handle the higher thrust and last significantly longer than a 12 volt system. if it requires 60 amp @ 12V to run a motor, it will only take 30 amps to run the same power motor at 24V. So a 24V system will last much longer....
  • Ankona SkiffsAnkona Skiffs Posts: 123 Deckhand
    24v @ 80lbs of thrust will be perfect. 36v @ 100lbs is overkill and 12v @ 55lbs will be disappointing
  • SnapperSlapperSnapperSlapper Posts: 137 Officer
    I have 24v 80 on my 18' bay with a 90. It yanks it around nicely.
    37 Seahunter "Dilemma"
  • Capt.AWCapt.AW Posts: 937 Officer
    You will be fine with a 24v80lb unit. I have that same unit on my 22' and it should work well on a lighter boat.


    Be very aware of your surroundings when using the anchor feature in an inlet, or tight to a bridge in heavy current. I don't know about the new Ipilots but the one I have will disengage the anchor feature if you're over stressing the motor without an audible warning. The only time you could possibly have an issue with the anchor feature would be during a spring tide.
  • JIMinPBJIMinPB Posts: 1,875 Captain
    The higher voltage motors are more efficient. They let you run smaller wires with less loss. More volts means less amps for the same amount of power. The down side to the higher voltage motors is trying to find a proper charging system for them, so that you don't need to take your batteries out of series & put them in parallel to charge them with a standard 12vdc charger.

    You can build your 24 or 36v battery bank out of 12v batteries, 6v batteries or individual cells. You can also buy high voltage dc batteries that are ready to go as-is. With your background, you have probably seen 24v batteries & maybe even 36v batteries in aircraft applications. In the case of a trolling motor, be 100% sure to get a deep cycle battery.

    To give you a rough idea of the efficency difference, consider this - If a given length of wire has a 3 volt drop across it, then a 12v motor will be running on 12-3=9vdc (75% of proper voltage) With the same voltage drop, a 24v motor would be running on 21vdc or 87% of proper voltage. A 36v motor would be at 33v, or 92%. In reality, the lower amp draw of the higher voltage motor will mean that it runs on less amps & will therefore have a smaller voltage drop across the same wire, so the effect is magnified even more than the numbers above suggest.

    Also, in theory, Volts x amps = watts and 746 watts =1hp. Electric motors do have some loss due to heat produced. so you never really get the full HP out of 746 watts of electric power going in.

    It's pretty important to choose the right size wires to prevent excessive voltage drop. It's not as simple as just buying 40 amp wire for a 40 amp load, regardless of the run length. https://www.bluesea.com/resources/1437 When using that chart, you need to figure 20 feet of wire to cover a 10' distance, because it would be 10' of black + 10' of red = 20' total for the current loop.
  • Salty GatorSalty Gator Posts: 1,829 Captain
    My set up is an 24 volt 80 lb Minn Kota on an 18 ft 115hp flats boat with a weight very similar to yours. It has plenty of thrust. The only time I would like more is if it really has to move against a strong inlet current. An onboard charger also makes recharging much easier.
  • SalteyDogSalteyDog Posts: 65 Deckhand
    Don't forget the weight of the battery and motor!
  • Osprey45Osprey45 FT Pierce/ Boonton Twp NJPosts: 997 Officer
  • maentmaent Posts: 20 Greenhorn
    For inlet fishing 24v/80 should be plenty. I use this motor on my 22 Skeeter bay in FPI with no problems. The I pilot system is awesome for this application. The biggest problem you will run into is inexperienced anglers getting lines in the moving prop. It will happen.
  • PaulBoatPaulBoat Posts: 4,389 Officer
    FWIW we put a 24v/80lb x5 MotorGuide on our new Redfisher 18 w/ 150 SHO (about 2000 lb dry) and it's amazing.

    Fished on it most of the day yesterday and didn't see the battery indicator move.

    Then took Joseph out for a couple of hours in the evening - current was ripping and wind had kicked up a bit... depending on how you're sitting against wind and current, the stern will swing a bit. Add a powerpole and if you're fishing shallow between trolling motor GPS lock upfront and powerpole in the back, you're golden.

    I have a powermania charger that came highly recommended by a couple of shallow water charter guys we've been with.

    Also see how much amperage your motor's alternator is putting out. This will help you charge when you're running between spots.

    b31891720ccb58678ce9d84dfe78985e.jpg
  • bandit100377bandit100377 Posts: 461 Deckhand
    Like someone else said, call Mike at master repair. I'll let him know to expect you. I think a 24 volt with 80 pound thrust should do you. Think about where you will mount the batteries and their weight.

    I called Mike and he said 24 volt, 80 pound thrust is what you need. 36 volt, 112 pound thrust is way overkill. Best way to reach him is stop in, or press option three on the phone message. It rings back in his shop.
  • Miki1956Miki1956 Posts: 12 Greenhorn
    New here so don't claim to know nuttin yet, but............well versed in RI rip currents. Did a lot of inshore and offshore striper fishing there.

    I always made it a point to overpower everything. For the only reason as to not have regrets.

    I have an 18ft Palm Beach center console with the 101 thrust Minn Kota 36 volt. Also put an onboard charger. What I loose in overall speed because of the extra battery(s) is well worth it. In RI, the moon tides were strong. I fished several areas where the rips were extreme and never had to worry. In a strong tide, I could easily fish (@70%) for a minimum of 6 hours straight without fail. And offshore fishing on humps had the same success.

    For the little bit extra you're throwing out on your investment I believe it's worth it. Coming home "with battery" is much better than having to leave because their drained.

    Just an old disabled yankee's opinion. Take it for what it's worth.

    Good luck. Hopefully you get what you need so you can get down to business.

    Tight lines!!
  • Andre cancillaAndre cancilla Posts: 103 Deckhand
    Have the 80lb thrust 24v on a 2001 19 ft key west sportsman. The 80 should be good for your boat
  • avmechavmech Jupiter, FLPosts: 1,373 Officer
    80 pound 24 volt, 20 foot bay boat that is on the heavy side, motor handles it very well. Have a look at MotorGuide Xi5 also. Have it and love it. Have it tied in to my GPS as an autopilot.
    Joined: Oct 7 2002
    Member #10822
  • Plane Fish nPlane Fish n Posts: 6,439 Admiral
    Great info here guys!!!!!!!

    Thanks much.

    Frank... is the Xi5 the one that says "GPS Positioning" and is that basically the same as iPilot?

    I have my eyes on a 2 year old Minn Kota Terrova 24 volt 80 lb thrust 60" for about $1000

    I can get a BRAND NEW Minn Kota Terrova 24 volt 80 lb thrust 54" for about $1200-$1300

    My next question is how to properly figure out if the 54" would be adequate including the inlet where it could get a bit sloppy or am I better off with the 60" which is a used motor?

    Thanks again guys for some GREAT GREAT info

    Eric
    PLANE FISH N
  • Capt.AWCapt.AW Posts: 937 Officer
    Get the 60. The 54 will pop out of the water in a moderate river chop.

    I would consider going to MG over the MK as well. I had so many issues with my MK that I will never buy one of their products ever again. My new MG just showed up 2 days ago.
  • Plane Fish nPlane Fish n Posts: 6,439 Admiral
    Capt.AW wrote: »
    Get the 60. The 54 will pop out of the water in a moderate river chop.

    I would consider going to MG over the MK as well. I had so many issues with my MK that I will never buy one of their products ever again. My new MG just showed up 2 days ago.

    Adam,

    What kind of issues did you have???

    Also, if the unit is used. Is there a way to test it without being installed prior to purchasing?

    Thanks much

    Eric
    PLANE FISH N
  • Capt.AWCapt.AW Posts: 937 Officer
    Unit was purchased in March of 2014. Since then I have had 6 control board failures, 2 drive motors, and 2 issues with the lower. Mike at Master Repair always made sure I got the unit back asap. This was the second trolling motor I bought from him and his shop wired the boat. Where I feel MR dropped the ball was by not going to bat for me with Minn Kota when I contacted them concerned that the unit was a lemon. The unit was clearly a POS from day one. I was told "You guides are too hard on them" or my favorite was "Most guides are buying two units so they have a backup".

    The only way I could see testing a used motor would be to hook it up to a battery and make sure it functions as it should. Knowing what I know now, I would not buy a unit used even if I were just recreational fishing. The 3 out of warranty repair were just under $1k
  • avmechavmech Jupiter, FLPosts: 1,373 Officer
    Eric, same idea, built in GPS, remote operated, can program route and repeat it or reverse it, etc.
    Joined: Oct 7 2002
    Member #10822
  • bandit100377bandit100377 Posts: 461 Deckhand
    You're welcome, DB. Mike could have answered all your questions in a minute. Don't cut off your nose to spite your face. Go to the expert.
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