Was reading an advertisement for a boat and they said it had a 2 speed transmission and TRS drives. Can someone give me the explananation in a nut shell of what that is?

A 2 speed trnamission allows you to "down shift" in the corners for better thrtottle control and accleration like you would in a car, then "upshift" when reaching higher speeds. It also allows you to keep the boat in it's peak power band RPM range for better fuel economy. Not running in to high of a gear and have the motor lug and using un needed fuel.

Now is this a bad thing? How come I don't see more set ups like this?

We used the 2 speed trans from B&M on my race boat Mr Technology.

At the first race, one trans stuck in first gear. They got sent back and rebuilt. At the second race, one got stuck in first gear during testing. We put on huge wheels and tore ass down the beach until one trans blew.

B&M was no help at all. They wouldn't help in any way, so out they came and Hubers went in. Never another trans problem.

Even Dragon Lady who was thier poster child used the B&M 2 speed trans but had 1st gear disabled becuase of this potential problem.

It was a good lite weight trans as long as you never used 1st gear.

All you have to do to is ask and this board knows

I have B&M two speeds on a cat with blower motors. They are automatic transmissions (Powerglide). They should not be shifted with a heavy throttle. The shift is done electrically with a button switch. My goal was to have a tremendous hole shot. The idle and no wake quality with the low gear is fantastic. The first gear is a low speed however, 60 mph is all there is in first and 130 in second on my cat. I am looking into transmissions with 4 or more gears for even more flexiblity. Multi-speed transmissions are (or were) used in offshore raicing in Europe. I am also surprised this has not caught on. Price might be an issue.

Dont forget you will need to move the engine 12"+ forward to fit it in between the engine and transom

Hyper baja brings up a good point about the extra room needed. I remember reading somewhere about that issue alone is why those transmissions are not more popular.

ahead 12 inches more ,even on a trs set-up? or bravo.

I would think that moving the engines 12" forward would change the center of gravity of the boat. This can be a problem if the boat was never intended for that C/G or its design is not flexible enough for this move.