Please Help with Trolling Motor

[KVH]

I really am handy with tools and mechanical things, including motors, but this one has me stumped!!

My Motor Guide 55 lb thrust became "dogmeat" about a year ago. I keep trying things: new batteries, tightening the cables, etc. I took it into a shop and the mechanic could only say, "It seems OK, maybe you just need a new one."

But even though it's now 8 years old, I really hardly used it.

Here's the thing: It's plain weak. Power is definitely better on 24 volts, but the big roar on 24 volts is mostly gone. I'm convinced something is wired wrong but I can't seem to located or find a problem.

On 12 volts the changing speeds (1 through 3) don't seem to do much. On 24 volts the speeds seem to change better, and high speed seems OK, but in the water the thing is a complete dog.

The shop says a new one is $800. I'm not ready for that. Is there something I'm overlooking. Do I keep cross wiring the thing wrong? Have I blown a component?

Advice please. thx

PS I have a dual charger in the boat.