I would suggest the Terrova......112 lbs thrust for a 20 foot pontoon. But someone with experience with a pontoon can better answer which size you need than I can. I would not get an Ulterra......I have an Ulterra and while I have to say it has served me well I have sent it in twice in 2.5 years and the last time I got it back was August 2017...it is already malfunctioning again. The repairs were done under warranty....and I have nothing bad to say about Minn Kota service and support. But my warranty is out and those previous repairs they put $2000 worth of parts in it....I did not pay for that. That is just to show how expensive parts for an Ulterra are. The Ulterra has a lot going on that can break. Many who have them have had no issues with them...but for those of us who have had problems they are a pain. If it malfunctions and will not stow it is a lot of effort to go through on the water to do a manual stow. Mine is still working and it will just be a matter of time before it fully conks out....but I will not put several hundred dollars to get it fixed....heck it will cost me almost 100 bucks just to send it back to Minn Kota since it is out of warranty...they paid shipping both ways when it was under warranty. There is no reliable service center close to me. I will probably get the 2nd gen Terrova before the Ulterra completely fails.
Regards
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