I have a small fountain motor (not submersible) plugged into a gfci and
After working fine for a year it now trips after about 10 minutes. This is
What I have tried so far.

1. I plugged a lamp into the same gfci and it stayed on for over 3 hours
Until I turned it off - didn't trip.

2. I then plugged the fountain cord into another gfci outlet that is on the
Same circuit with an extension cord and it tripped after about 10 minutes
Too.

3. I then plugged the fountain into a non gfci with an extension cord and
It ran for hours, no problem.

When the fountain trips at least 2 other outlets in my house no longer work
(that I know of).

Can you tell me what I might be missing or how to further troubleshoot this?

Because you have tried two different gfci outlets and they both do the same thing, I would guess the gfci is sensing a minor ground fault in the motor and doing what it is supposed to do. Finding out that the motor would run for hours on a non-gfci outlet tells me there must be a minor ground fault in the motor or the wiring. I have found gfci outlet boxes full of rusty water and insects which were causing the problem. The only other thing might be that the motor is drawing more amps than the gfci is rated for. These are difficult problems to solve and I would not by-pass using a gfci for safety reasons. Wish I had an easy answer for you but these can be a bear to find.

Thank you. I have since changed the GFI to a regular outlet and it is running perfectly. A to the safety, the fountain is in an enclosed area and to one goes near it. When I do to clean it, all power is off and I am nowhere near the outlet. OK?

That is not code but is probably the same thing I would do at my own home. Anytime there is water and electricity in combination, a gfci is required by NEC and most local building codes, but if you are OK with it not having one your problem is solved.