I have a small Jon boat about 12" and wonder if there is a big differences in speed (mph) when you previously had a 55 thrust compare to a 80 thurst. Currently have the minnkota 55 and maybe looking for a stronger trolling motor (80) but seeing if it's worth the cost to upgrade. 

Would prefer someone who had upgraded their trolling motor on the same boat for more accurate advice. Although all advice and personal experiences is welcomed. 

My 19ft ranger has a 82b thrust motor guide. I don't fish rivers, only lakes. My 82b thrust is more power than I need all day long. I usually only have my motor on power 6. If you don't fish current, 80 lb thirst would be overkill. And that goes against my general rule- get the biggest motor (gas or trolling motor) that you can afford. I would only consider the 80 if it was your only source of power and you fish big lakes. Otherwise 55 should more than suffice. 

It would be "faster", but adding a second battery will add weight. The bigger advantage would be battery life, and longer life of the trolling motor itself.

This would be my only power source on the boat. I guess my main question is how much a differences in speed it does especially for those who have upgraded on the same boat/weight unit. 

I can't imagine needing more than 55lbs of thrust on a 12 inch  or a 12 foot jon boat unless you're fishing in some serious current. 

Is the trolling motor the main propulsion for the boat? If so, the 80lb may get you to your spots marginally faster. As @BrianinMD stated, your battery life will be much better with a 24v system, but it will double your battery weight. 

edit: 

Just saw your most recent post.

Is this for an electric only lake/river? You can get a good used gasoline outboard in the 3-10hp range for about what you'd pay for a new 80lb trolling motor. I'd keep the 55 and buy a gas motor, if you're not restricted on your home water.

For now I would like to stick with just the trolling motor because of electrics lakes also. I just like to know speed differences if someone had that on personal experiences. 

As mentioned, would not be very practical in most cases. 

Your 55 is about a big as they come in a 12 volt, you didn't say but figure a 12V is what you are running.

To go bigger means another battery.  Unless it's a mighty wide 12 (foot) jon, that means you will have to have at least one if not both batteries, if in the boat by yourself, up at the front seat or you would be riding around with the nose up in the air at about a 45 degree angle from all that weight in the back. You can figure close to an additional 75 pounds in the boat.   Also makes the boat want to just go around in circles when trying to fish. 

I got rid of two transom 12V 55# thrust for my Tracker and replaced them with a single 24V 80# transom motor. I go faster. Used the same two batteries.

I do the transom motor deal when fishing electric-only waters.

I made the mistake of assuming two 55# thrust motors could about equal my bow 105# 36V motor. All it was doing was dragging the transom motors since they could not keep up. Got a little boost when running the bow motor about 1/2 speed.

The difference is RPM's.

Last year, I had both of my bow 36V motors rebuilt (one is a spare) and changed to 24V 82#. Haven't checked the MPH, but at least I am not dragging the transom 80# like I was when running the 105# WOT. One less battery also.

Was this on a 12 foot boat?

16 minutes ago, Way2slow said:

Was this on a 12 foot boat?

If that question is for me, no, a 16' Tracker and replied as per the last sentence in the original post:

" Although all advice and personal experiences is welcomed."

You would pick up some speed. I've never run a motor that big on a 12' john boat, but I upgraded from a 45 lb thrust to an 82 lb when I had my 16' Ranger. It did increase in speed but not by a huge margin. Given that it's your only mode of propulsion though a bit of an upgrade is better than nothing. 

It's tough to give a "speed difference". On any given boat it would be different.  A 12' tin boat would be different than a 18' glass boat as far a weight. Will you notice a difference in your boat with a 80lb TM, yes. In a 18' glass boat, yes, but not as much. A full gas tank and a couple of tackle bags and a fishing buddy will make a difference. Too many variables to come up with a "speed difference".  

I have a 55# on my inflatable that is 12' size. I say if your back can handle the 2 batteries of sufficient size go 80#thrust route. Im now thinking of going 2 batteries (size 24) with my boat. I want the smaller size battery for less weight that i have to lift at once, a 40pound battery is easier on my back than a 60pound battery.

I had a 14' jon and think it could handle 2 batteries easily

A single size 24 bat  with 55# thrust doesnt last as long as I would like. It scoots ok full tilt but sucks battery. I go on 40-300 acre size lakes

Here my boat