Check out the Kato motors, they're relatively inexpensive yet are "very" high quality. Use the ones for the "road" diesels, not the switchers unless you are remotoring a switcher.
I have used them for years now since the "old" NWSL motors became unavailable quite some time ago, the newer ones just aren't as "healthy" as the older ones. I've also used them in my brass engines and they work great so they should do a fine job in your Bowser steamers as well.
Mark
I'm not sure where my old thread went, so I figured I'd write a new one. My Helix Humper replacement motor and mounts came the other day to replace the old messed up motor and mounts in my really old Athearn blue box PA1. So I pulled the flywheels off of the old motor, install everything (after cutting out the frame to make room for the new motor), solder it all together and it all ran without issue. Performance wise I would say this particular motor is on par with the original gold ones. I have an old late 80's GP9 with the gold motor and plastic side frames and now this engine performs the same, both in sound and slow speed performance. Now it may be skewed some since I have lighted passenger cars. I am also running DC and not DCC right now... so perhaps that would improve down the road. Overall, I'd say it runs decently, though. I'm not sure that I'll go out and replace all my blue box motors with these, though. I'm thinking about just going for the "high performance" gold motors instead. They're about the same price. Thoughts?
I am debating about using these in my Bowser locomotives down the road as I slowly replace the old DC71 motors. I want to see how this one performs and holds up first, though, especially since there are alot of mixed reviews out there on them.