Just bought a boat, its a 18ft Gemini for those that havent heard or seen one its the same as a laser.. It has a 45 pound thrust TM on it, havent had the chance to take it out much and use it, any advice how this TM will do? Its only 12 volt

I ran a 55 lb., 12 volt trolling motor on a smaller boat for a couple years...I would have loved more power and it was almost always running low on battery power by the end of a day on the water.

I've been running a 101 lb., 36 volt Minn Kota Terrova for several years on three different boats (Lund Pro-V 1800, Crestliner Pro-Am 1750 and a Crestliner CMV 1850) and I really like the power and battery life...I've never even been close to running out of battery charge on some very long days, even in current or strong wind.

With all that in mind, I'd go with at least an 80 lb., 24 volt system on a boat the size of yours...and I wouldn't hesitate to go to a 36 volt system at all.

I can't ever recall anyone being unhappy they had too much power with a trolling motor.

I think the best thing is to take it out and see how it does. If you don't need to replace it then don't. 

As was said though, you don't hear about people wishing they had less power.

Give it some time. If it's not getting it done then replace it. 

24 volt system and at least a 70lb. I have an 80lb on 18' 9" Stratos and it's about perfect.

The only thing that 45lb 12V system is going to do is let you down.

8 minutes ago, Bluebasser86 said:

24 volt system and at least a 70lb. I have an 80lb on 18' 9" Stratos and it's about perfect.

The only thing that 45lb 12V system is going to do is let you down.

Couldn't agree more. That 12v is gonna burn down on you fast, especially if in wind or current. TM is something I always say I'd rather have to much run it on 50% than have it die on me 4-6 hours into a tournament. 

If you can't afford a new TM and you're running the single battery down, add a second battery (connected in parallel) to double your reserve time.  You would need to replace the current one so that you would be starting with two fresh batteries that are equal.  Much cheaper than a new TM if the current one pulls the boat along ok.  My current setup is a MG 54# running on two BPS 175 batteries.  Have run them all day on 4 and 5 without coming close to draining the batteries. 

You could also look into having the motor checked out.  Brushes get old and worn, leading to lower performance. 

3 hours ago, Ohio Archer said:

If you can't afford a new TM and you're running the single battery down, add a second battery (connected in parallel) to double your reserve time.  You would need to replace the current one so that you would be starting with two fresh batteries that are equal.  Much cheaper than a new TM if the current one pulls the boat along ok.  My current setup is a MG 54# running on two BPS 175 batteries.  Have run them all day on 4 and 5 without coming close to draining the batteries.

I did this for a while with my 55 lb. trolling motor.

It definitely increases battery life and is a good step until a 24 or 36 volt system fits in the budget.

90% of your trolling motor usage is normally on the lower power setting to control the boats position.

If you are the type of angler that puts the TM down and runs the bank constantly moving you need 2X the power and 2 to 3 12v batteries.

Tom

power to boat ratio for tm should be however big you can get and fit on it regardless the size of boat. I had a 45 lb thrust tm on my last boat when I got it. It was a 15' 10" fiberglass and even with that small of a boat I got blown off spots when it got windy. I stepped it up to an 82 lb thrust and never had that happen again. Was it overkill...most of the time, but there where times I used every bit of power it had and was very happy I had it.

6 hours ago, WIGuide said:

power to boat ratio for tm should be however big you can get and fit on it regardless the size of boat. I had a 45 lb thrust tm on my last boat when I got it. It was a 15' 10" fiberglass and even with that small of a boat I got blown off spots when it got windy. I stepped it up to an 82 lb thrust and never had that happen again. Was it overkill...most of the time, but there where times I used every bit of power it had and was very happy I had it.

EXACTLY

Bigger is better 

A good rule of thumb for an 18 or 19 foot boat is a minimum of 70 - 80 lbs of thrust and 24 volts.  If you had a 20 or 21 I'd go with over 100 lbs and 36 volts.  Your setup may pull that boat around, but a wind of 15 - 20 mph and above is going to overwhelm 45 lbs of thrust for a boat that size.  You may be able to set it on maximum speed and handle some wind, but it is preferable to be able to handle the wind with a speed that gives you more control.  Not to mention that fighting a windy lake with your TM on maximum speed will take your 12 volt setup down to nothing much more quickly.