So I have a little 14' fiberglass boat with a 12v 45lb thrust Motorguide TM. I fish a couple reservoirs where it is electric only, and I've never made it out to some parts because it would take like 30 minutes just to get there. My typical outting is only 2-3 hours with my kids, so I usually try and get them fishing right away.

 

If I get a 12v 55lb thrust TM, will it actually increase my speed? Or is thrust like torque, where it doesn't necessarily translate into raw speed, just more pulling power. I'm hesitate to go to 24v because I don't think there's room to add another battery. 

 

 

As long as the boat and the load doesn’t change, more thrust will increase speed. In your case, increasing the thrust by 10, isn’t going to make a big difference. Going to a 24 volt, 80 lb thrust would give you enough of an increase to make it worth the conversion.

Thrust is relative to speed. I never felt efficient at all in my boat until I got into a 24v TM. I had a 46# Motorguide and couldn't stand it. If you can make it work, definitely get the biggest you can afford in 24 volt. 

Thanks for the info. I think I'll upgrade to the 24v/70lb Motorguide, it would be nice to get to places faster on those reservoirs.

 

My only hesitation is if I have the new 70lb TM, and I want to crawl the boat, it may have too much power and go faster than I would like on the lowest power setting. On my current 12v/45lb TM, I don't ever recall using it on the lowest power setting, and more often than not, power 3. So maybe power 1 on the 70lb TM will be slow enough.

I run an 80lb Fortrex on my boat with speeds 10-100. #10 is the slowest, and I'm pretty sure it doesn't even move my boat. 

On the lowest setting you'll barely even feel the boat moving. I have a 19ft ranger fiberglass and my ultrex 80 thrust on setting one wont even move the boat. 

You will see very little increase in speed going from 45 to 55. I only gained around .5 to .75 mph faster on my pond prowler going from a 30lb motor to a 55. I can see a big difference in pulling power in the wind though.

If you get a motor with variable speeds instead of one with 5 speeds you can make it crawl.  I have a 112# 36 volt and can make it go so slow you would think I was anchored.

More voltage = more power, more power = more thrust 

If you have 12 volts and 45 lbs thrust at full power vs 24 volts and 45 lbs thrust at 50% power your battery life is increased 50% or twice the running time.

The only way to increase run time is increase voltage or amp hours or larger size battery capacity.

Group 31 AMG marine 12V  about 65 lbs. and your best choice.

Tom

PS, before 24V TM we used 2 T125 6V batteries in series and could run at full power for 2 days! 

22 minutes ago, WRB said:

More voltage = more power, more power = more thrust 

If you have 12 volts and 45 lbs thrust at full power vs 24 volts and 45 lbs thrust at 50% power your battery life is increased 50% or twice the running time.

The only way to increase run time is increase voltage or amp hours or larger size battery capacity.

Group 31 AMG marine 12V  about 65 lbs. and your best choice.

Tom

PS, before 24V TM we used 2 T125 6V batteries in series and could run at full power for 2 days! 

Thanks - runtime isn't important to me, so much as top speed is. I am going to remove the spare fuel tank in the transom well to fit another AGM to upgrade to a 24v. I don't fish on the gas engine enough in a day to use all 5g anyways.

 

My old TM had a 36" shaft,and when full down, it was about 16 inches under the water line. When trimmed up, it ran 3-4" under the water line which was great for getting into skinny water. It had some kind of plastic ring stop inhibiting it from trimming up past a certain point. Boat draft is about 10".

 

I can only find 24v batteries with a 45" shaft, and I won't be able to get into that skinny water anymore unless I can trim up the TM to where I want to.

39 minutes ago, Junger said:

 

I can only find 24v batteries with a 45" shaft, and I won't be able to get into that skinny water anymore unless I can trim up the TM to where I want to.

 

Someone must sell a stripped sunshirt. 

Motor Guide R5 24V digital 70 lbs or 80 lb w/42" shaft transom mtg that can be raised up, check with MG how high. 5 speed forward, 2 speed reverse.

Tom

Having more thrust will get you on plane faster.  KIDDING!!!!!!

Something like this will turn your 5 speed TM into a variable speed motor that will run as slow as you like. Just hook it between your battery and motor.

 

KNACRO DC Motor Speed Governor 12V 24V 36V 48V (10-55V) 60A Forward/Reverse Switch Digital speed scale 0-100%

 

https://www.amazon.com/gp/product/B06XDHF6M1/ref=ox_sc_saved_title_6?smid=A1OB26G8TSLEZQ&psc=1

I've got a Minn Kota Terrova 80 lb on my 1448 jon boat and it'll cruise at 4.3 mph with a heavy fishing load. If you go with a 24 volt I'd suggest 80 lb over 70 lb thrust.