Got a Mini Kota 80 Maxxum Pro . It has a popping in it when you give it power if it is above 50 -I replaced the Bow Guard but it didn't help - any past experience with such a problem

I havnt had that problem but I think if it is under warranty you should get it fixed. doesn't sound right

is it only when first engaging power?

i had a loud pop every time i stepped on the button, it was because i had replaced the shear pin and the replacement i used was a smaller diameter pin, so there was some play when the prop would first engage. cleared up when i put a thicker gauge pin in it.

If its the bracket popping there's no good way to fix it. I have a 101 MK hand control and if I have the thrust up over about 25 - 30% the torque when I hit the foot power button makes the bracket pop. You can try putting some grease on all the inner workings but on my last boat they replaced the entire bracket twice and minnkota finally admitted they couldn't fix it.

Only way I fixed that one was to replace it with a motorguide -

I replaced the upper arm assemble that helped some, it seemed to be coming from where the release/engage pins were. I placed a couple of thin felt pads next to the engage slot on the flat close as I could but not in the slot... It's been wroking great, stiffed up the conection and all is good again.. You may have to experiment on the thickness, mine was worn .050-.070 thousands.. I'm using a 100 thousand thick piece of felt.. Good luck