So im buying a boat and it currently has a really old Trolling motor on it.
I'm already shopping to replace it and my main question would be if 80# is plenty to move well on a windy day in a 18 ft fiberglass boat.
My second question would be the shaft length and if a 45" or 50" shaft pretty universal for an average bass boat.

80 should be plenty if you don't get a deck boat that's a giant sail. Best of luck with new boat.

Oh yes and 45" shaft should be good . Motor needs to be 12"s below surface when deployed ifI remember correctly.

Oh yes and 45" shaft should be good . Motor needs to be 12"s below surface when deployed ifI remember correctly.

If you are going to fish even on days that get a bit windy, I recommend a longer shaft on the TM. That way you can drop it deeper to prevent it from constantly coming out of the water with each wave.

I Appreciate all the comments and insight. Was just worried about buying a $1000 TM and it not be the correct one!
Thanks again!

Go to minn Kota site and they have a chart on measuring for shaft size if you are unsure. Make sure you have a little extra if you'll ever be out on windy days

I just pulled my MinnKota Maxxum 80 45" off to replace it with a new MinnKota Ulterra 80 45". I'm 71 years old and can use all the help I can get thus the Ulterra. I have a 20' Nitro with a Mercury 225 and the 80lb is a good match are I would have bought the larger tm this time around. If your are interested in my Maxxum take off shoot me a pm. I run two big AC brand batteries and my boat will jump with a 80lb on it.

On that size boat, the 80 will be fine. Most bassboats use a 45" shaft, with exceptions made for fishing in the wind, or boats such as Skeeter and Champion that set "bow high" in the water. Let me know if I can help.
John