If you were strapped for cash and had to choose between the following two situations which would you chose.

1. Get the 997 SI unit and use your crapy old transom mount 40lb trolling motor for the next year while saving for a new $850 trolling motor.

2. Get the $850 trolling motor and a $200 fish finder and save up for a year to get the 997 SI unit.

There are lots of Minn Kota and Motor Guide T/M that cost a lot less than that. I have a 24V M/K that was 659.00 two yrs. ago. What are you buying that cost that. Buy the 997(I just did) and unless your fishing out of a 22' boat, and I assume your not since you now have a 40# thrust,  you may be fine. JMO

Good points. I am going to go back and reword the question to reflect better pricing.  looks like your vote is for the 997 SI first.

When I can afford it I want a bow mount foot controlled. Digital Auto Pilot trolling motor. The cost of another battery and any installation parts is in that estimate. 55 or 70 lbs not sure yet.

That makes sense. Mine is a hand operated unit. I prefer them over the foot . The cable on the foot operated unit has broken for the last time on me. Mine is a 70# and it pulls my 19'10" boat great. JMO.

I am going to back up. If you are using a transom mount T/M, go ahead and purchase the T/M first.

In my opinion a new SI sonar unit will help you catch more fish NOW.  A new engine will help get you around faster but I dont think it will be as big an improvement as finding spots you wouldnt even consider w/o knowing exactly whats down there.  Just my 2 cents feel free to disagree  

Surfer  

Before you buy a Humminbird SI drop me a noite.  I may be able to save you some money on one.  That also go for any one else.   Bud