I need some help with nitro questions. I know very little about nitro engines, so here it goes.
I have a os 50 that I have been flying for the last 6 years without issues, and love the engine. Last year it started making some not so nice noises at high rpm’s. This winter I was lucky to find a almost new 50 to replace my last one.
Today I ran it on a new fun fly(twist is what I alway use) bird I built and it sounded like a old ford down a dirt road.
I then tore it apart and noticed the main bearing was rusty and noooo good.
I watched a YouTube on how to remove the bearing and now I am to the point of finding new ones. Tower has them (both) for around 40 bucks, but I cant tell for sure if I am getting the right size. I think so though.
I remember Boca always advertising on this site and tried to search for them.

Should I stick with towers and pay 40 or go with the boca?
Does anyone know about my 50? and can confirm if its a 15x28x7mm bearing?
I noticed there are a couple different 50’s out there??
sx? mine only is stamp with a 50 on the case??
jason