I'm new at this .a little info would be great. i bought 2 identical 25 trainer one almost ready to fly and the other to build(spare parts) . i've installed golden rods instead of the wooden dowels. right now the ARF plane has a futaba sky port 6 radio and servos installed (that i thought it was a good price). everything works great and has the right amount of movement according to the manufacture . i have a flying club that i am going to join about 40 km. it seems to be everybodies suggestion .my question is can i put a 40 or 45 engine in a 25 plane or is that over kill

It is considered 'overkill', but I've seen it done. Just be light on the throttle..

where you from,eh?! Which club you joining?

You can put a diesel V-8 in a cigar box and it will go like mad. Seriously though, how much you can "over power" you airplane depends on a lot of things. #1 structure of the engine mount and firewall. #2 what is the altitude of the field where you will fly. I fly at 5000' ASL and have put .15 engines in a QT that is designed for an .049 after adding a bit more wing and tail feathers. It flew great.
Usually you will find engine size listings on the kit or somewhere in the instructions. I have always found it more efficient to use the largest sized engine suggested. If you fly from a field that is over 2000' ASL you could easily support a .35 engine. If it's a hot day even that may not be enough. If you are a full scale airplane driver you know how to determine pressure density altitude. If not it might be worth the study. Much good luck !

I had a 32 in a 25 sized plane, and I'm only about 300 feet above sea level. It was a very enjoyable plane setup like that. That summer the club thermometer hit 100 in the shade, so it was just about right with that 32. With the right prop, you could get away with a mild 40, but keep in mind it will add weight and will mess with your CG.

man you people are fast. thanks for the info . the engine calls for a 10 X6 prop a thunder tiger 40 or 45 from a friend if it's to heavy i'll have to add some weight to the back . does CG have to be done with no fuel in the tank .i'll detune the motor with the throttle linkage thanks again

As long as you can get it to balance and have a good teacher go for it. Just run it about 1/3 power.
You might also check the ground clearance. A .40 will run a 10 or 11 inch prop. later daveo

Balance with the tank emplty. It's better to have a noze heavy plane than a tail heavy plane..

Another thought, is that if you have the tank reccomended for teh .25 / .30, and you're running a .40 - .46, your flight times might be a little shorter than anticipated. have a freind time your first few flights, and use that as your 'flight time'.