Trolling motor question

[Basshunter387]

I have a tracker 1648. All electric motor. I have one 80lb thrust on the transom. My question is for more top speed would I be better off getting another 80lb thrust and adding batteries or just upgrade to a 36v 112lb?

[Gundog]

Lighter means faster. Upgrading to 36v would be lighter than having 2 TMs and 4 batteries. IMO get the 36v and it would be easier to charge the batteries as well. 

[sully420]

I agree with gundog

[Jig Man]

14 hours ago, Gundog said:

Lighter means faster. Upgrading to 36v would be lighter than having 2 TMs and 4 batteries. IMO get the 36v and it would be easier to charge the batteries as well. 

X2

[Further North]

I was going to jump on the 36 volt bandwagon (because I'm a 36 volt guy)...but then I started thinking about the math...

 

2 X 80# Thrust is really 160# thrust...

 

1 X 101 (or whatever Motor Guide is) is...101...

 

Battery weight (I'm going with Interstate 29 series as sort of an average, and rounfing up to 60# for easier math) for 2 X 80#: 240#

 

Battery weight for 1 X 101: 180#

 

So...

 

2 X 80# gives us: 240#of batteries/160# of thrust = 1.5 pounds of weight for every ft. lb of thrust.

1 X 101# gives us: 180#of batteries/101# of thrust = 1.78 pounds of weight for every ft. lb of thrust.

 

Seems that adding a 2nd 80# TM would be better, everything else being equal.

 

I'd go 36 volt, 101# thrust every single time, if I had one TM. 

 

Given the choice between adding a 2nd 80#, and replacing my existing 80# with a 101#...given the constraints of the original question...I'd add a 2nd 80#.*

 

*What I'd really do is find someplace to fish that wasn't electric only...but some folks don't have that option.

 

Edited to replace 112# thrust with 101#, because the MK Vantage isn't offered in 112#.  All changes are on bold.

 

 

 

[Gundog]

36 minutes ago, Further North said:

I was going to jump on the 36 volt bandwagon (because I'm a 36 volt guy)...but then I started thinking about the math...

 

2 X 80# Thrust is really 160# thrust...

 

1 X 112 (or whatever Motor Guide is) is...112...

 

Battery weight (I'm going with Interstate 29 series as sort of an average, and rounfing up to 60# for easier math) for 2 X 80#: 240#

 

Battery weight for 1 X 112: 180#

 

So...

 

2 X 80# gives us: 240#of batteries/160# of thrust = 1.5 pounds of weight for every ft. lb of thrust.

1 X 112# gives us: 180#of batteries/112# of thrust = 1.61 pounds of weight for every ft. lb of thrust.

 

Seems that adding a 2nd 80# TM would be better, everything else being equal.

 

I'd go 36 volt, 112# thrust every single time, if I had one TM. 

 

Given the choice between adding a 2nd 80#, and replacing my existing 80# with a 112#...given the constraints of the original question...I'd add a 2nd 80#.*

 

*What I'd really do is find someplace to fish that wasn't electric only...but some folks don't have that option.

 

 

 

Not sure if you included the weight of the second TM. Also I'm bad at math.

[Further North]

1 minute ago, Gundog said:

Not sure if you included the weight of the second TM. Also I'm bad at math.

Good point.  Off to check...couldn't find the weight of the 80# vs 101# Vantage on Minn Kota's website....and tha drop to 101# will change my math above a  little.

 

Found this, which might be the best overall solution: https://minnkotamotors.johnsonoutdoors.com/electric-outboard-motors/electric-outboard

 

...assuming Minn Kota is the target brand.

[Jig Man]

If you go for 2 trolling motors, have you given thought as to how you would operate them at the same time?

[sully420]

2 80lb trolling motors? Where are you going to put 4 batteries in that boat? how will it effect the boat? How wll you steer two trolling motors? It just seems more trouble than its worth and not too practical. I have a 16" tracker and a 80lb ulterra and i get 3mph out of it.

[WRB]

You can run both 24V trolling motors with 2 (12V) batteries at the same time, the amp draw is doubled when both are running. I don't believe you will be running both TM's at the same time all the time? 2 Group 31 AGM batteries weigh about 130 lbs.

Tom

[Toad Master]

Interesting topic. More lb thrust does not mean more speed. I was running a 24v system with an 80# Motorguide xi5 with 4 batteries 27 series. 2 batteries per bank and was getting 4.5 mph, I switched the prop. to a 3 blade and got 6.2 mph.   I had a great opportunity on a 112# 36v Minnkota Ultrex (new) and with the same boat set up only got 4.7 mph with 2 blade prop. wanted to try it with a 3 blade but was unable to find a prop. for that size motor.  I fish an electric only lake that is 5 miles long and want the speed for more fishing time and not running time. Running long distances on high with just 2 batteries (24v I would run out of power in 6-7 hrs. especially on windy days, this is why I was running 4 batteries. I read an article a long time back about how Motorguide and Minnkota tested and got their ratings for lbs of thrust at the time (I don't know if this is true today) both companies tank test with a scale in the prop. wash I don't remember how far back. Motorguide waited for the prop. wash to settle after the initial start of the motor and took the scale reading while Minnkota took their reading from the prop. surge upon startup. Like I already stated I don't know if both companies are still doing it this way. But I do find it interesting that my results are the way that they are. I wish I could find a 3 blade prop. for the Ultrex to see what it does compared to the 2 blade which is currently on the motor. Weight was a concern of mine also but the speed I was getting with the Motorguide made the weigh worth it IMO. 

[Further North]

Were I on an electric only lake, I'd be looking at those electric outboards that popped up here a while back.

[LonnieP]

More thrust isn’t going to you much more speed. If you want to go fast you’re going to need an outboard.

[Further North]

1 hour ago, Toad Master said:

I had a great opportunity on a 112# 36v Minnkota Ultrex (new) and with the same boat set up only got 4.7 mph with 2 blade prop. wanted to try it with a 3 blade but was unable to find a prop. for that size motor.

https://www.kipawapropellers.com/store/p13/Kipawa_112_Three_Blade_Propeller_-_Minn_Kota.html

 

https://www.amazon.com/Kipawa-112-Weedless-Performance-Propeller/dp/B00ZHC4ZCU

 

I've not tried them, but have been tempted.

 

I would be more interested in extra thrust for rivers, rather than speed, but it might do the trick.

[LonnieP]

On 4/8/2018 at 7:35 PM, LonnieP said:

 

 

[Brad in Texas]

On 4/7/2018 at 3:14 PM, Basshunter387 said:

I have a tracker 1648. All electric motor. I have one 80lb thrust on the transom. My question is for more top speed would I be better off getting another 80lb thrust and adding batteries or just upgrade to a 36v 112lb?

I see different explanations. I'd only add that thrust and top-end speed aren't the same. Your original question regarded increasing top speed.

 

Imagine two 300 lbs. offensive linemen together pushing a loaded Kroger grocery cart across a flat parking lot. Each man, while very powerful, has a top running speed of 18 miles an hour. No, two of them collectively pushing on a single chart will not make it go 36 mph. No. Top end speed will essentially be, for two men, what it'd be for one.

 

But, these two big men "could" overcome the inertia of, say, a cart loaded down with 1000 lbs. of barbell plates. Here, more "power" would make a huge difference.

 

So, two 80s aren't likely to net you much top speed increase. It would certainly increase thrust, power going from a dead stop up top speed. A single 112 lbs. TM might net you more top speed . . . but it'll depend on its design characteristics.

 

Brad

 

 

[Gundog]

1 hour ago, LonnieP said:

 

I agree wholeheartedly. 

[LonnieP]

18 minutes ago, Gundog said:

I agree wholeheartedly. 

Haha my phone accidentally posted and I couldn't figure out how to delete it ?

[fissure_man]

@Brad in Texas Interesting analogy but I would add a bit more to it.  “Thrust” is a characteristic of the motor, but “top speed” is a characteristic of the boat + motor + propeller package.

 

To be fair to your analogy, a given TM does have an inherent speed limit based on the max RPM and prop pitch (anecdotally around 5 MPH, but I assume this must vary a bit?).  If the OP is already cruising at this max speed, adding a duplicate TM isn’t going to do much.  This is the “two linebackers pushing an empty shopping cart scenario.”  People sometimes encounter this when putting a TM on a canoe or kayak with low drag – there is power to spare, but the motor speed is maxed out (same as running too low a pitch on a regular outboard).  Changing to a higher-pitched prop should help in this scenario (conceptually); are these available?  One of the posters above had a good experience by changing the prop.

 

If the boat is under-powered and not reaching max TM speed due to drag, adding more thrust would help the top speed, the amount depends on how severely under-powered it is.  In this case, reducing drag via weight would also help, and the trade-off of thrust vs. weight needs to be considered.  Driving into a strong headwind is a realistic scenario where adding thrust with a second motor or bigger motor would increase top speed, possibly significantly if it’s very windy.

 

At TM speeds, the boat is not on plane and is pushing water.  Approaching planing speed, going a little bit faster adds a lot of drag.  In other words it takes a (relative) lot of added force pushing the boat along to counteract drag and achieve small increase in top speed.  Adding more battery/motor weight worsen(s) the drag vs speed relationship because it pushes the hull further into the water and this also needs to be factored in.  The specifics of all of this depend on the hull and weight (+distribution) of the boat to begin with, but it’s a game of inches.

 

All of this would be pretty onerous to calculate, but suffice to say, no number of stock MK or MG trolling motors is going to have you going faster than their inherent limit (~5 MPH?), maybe a bit more if faster propellers are available.  An electric outboard like a Torqueedo is built for this purpose and is a better option, but $$$.  A pair of oars would be relatively cheap…  

[Brad in Texas]

31 minutes ago, fissure_man said:

@Brad in Texas Interesting analogy but I would add a bit more to it.  “Thrust” is a characteristic of the motor, but “top speed” is a characteristic of the boat + motor + propeller package.

 

To be fair to your analogy, a given TM does have an inherent speed limit based on the max RPM and prop pitch (anecdotally around 5 MPH, but I assume this must vary a bit?).  If the OP is already cruising at this max speed, adding a duplicate TM isn’t going to do much.  This is the “two linebackers pushing an empty shopping cart scenario.”  People sometimes encounter this when putting a TM on a canoe or kayak with low drag – there is power to spare, but the motor speed is maxed out (same as running too low a pitch on a regular outboard).  Changing to a higher-pitched prop should help in this scenario (conceptually); are these available?  One of the posters above had a good experience by changing the prop.

 

If the boat is under-powered and not reaching max TM speed due to drag, adding more thrust would help the top speed, the amount depends on how severely under-powered it is.  In this case, reducing drag via weight would also help, and the trade-off of thrust vs. weight needs to be considered.  Driving into a strong headwind is a realistic scenario where adding thrust with a second motor or bigger motor would increase top speed, possibly significantly if it’s very windy.

 

At TM speeds, the boat is not on plane and is pushing water.  Approaching planing speed, going a little bit faster adds a lot of drag.  In other words it takes a (relative) lot of added force pushing the boat along to counteract drag and achieve small increase in top speed.  Adding more battery/motor weight worsen(s) the drag vs speed relationship because it pushes the hull further into the water and this also needs to be factored in.  The specifics of all of this depend on the hull and weight (+distribution) of the boat to begin with, but it’s a game of inches.

 

All of this would be pretty onerous to calculate, but suffice to say, no number of stock MK or MG trolling motors is going to have you going faster than their inherent limit (~5 MPH?), maybe a bit more if faster propellers are available.  An electric outboard like a Torqueedo is built for this purpose and is a better option, but $$$.  A pair of oars would be relatively cheap…  

Yes, and what I mentioned, you added to, is what we see all day long with kayaks/canoes. We are so bounded by hull speed limitations that, yes, a larger TM will get us a bit more top-end speed, a faster prop, a sleeker design . .  but speed increases at a great increase in energy to get that last mph. The old say that a canoe under power is like "pushing a wet mattress across a lake" is operative here. Brad