power loss in upper speeds in my trolling motor???

ok ok, Im stumped..... need some help before I toss this thing against a wall. I have a 45lb trust MK tilller 5spd forward 3spd rev transom mount..... on the water yesterday, fighting against the wind I noticed my trolling motor suddenly lose power at the high speeds but would operate fine at low speed setting..... reverse was not affected at all??? I pulled it apart and checked resistance on all points ..... everything checked good...... does any one have any ideas were the gremlin might be??? or can I maybe wire it direct for high/low forward and high/low rev??

 

i thought of that as well, but dont seem to see a way to dismantal the controler inside the handle..... i have looked online and cant seem to find just that part listed alone anywere...... any ideas?

 

No I dont lose total power, in fact I did some testing again last night using a trash can for a run tank..... in the low speed settings I seem to have normal function, but once I go into spds 3-4-5, it does one of two things..... either instantly drops prop speed to that of spd 1, or goes to normal full speed then quickly drops back to low speed......
lol I really have been happy with this little TM and other than a couple little scratches you would think its brand new, never would guess its 4 yrs old. it just does such a great job on my classic that i hate to have to get rid of it.

 

you know, that is prob the only test I didnt do......... i checked the batt at full charge.... but never thought to test it across a load...... thanks

 

thanks for all the help..... seems everyone was correct.....LOL battery had to bad cells.... so new battery went in, same issue..... pulled it all apart again, and found the control had a dead spot too after all.......
glad i can count on others when my brain stops working..lol