I am currently running a LH 26 B1 on my XR drive, just touching the rev limiter at 5350 rpm. I plan on adding 100-150hp over the winter and i am sure I will have to go up to a 28" prop. My question is, is the drive stronger running in RH rotation. I have read that LH pushes up on the top cap and is weaker that way. Any truth to this. Thanks, Joe

Yes, that is basically true. Left hand rotation does push up on the top cap. You can fix that problem by running a good top cap, such as the one Teague makes..

http://teaguecustommarine.com/index....t-top-cap.html

I don't care to switch to RH rotation, but was told by Advantage that my boat performs better with LH rotation according to some testing that Bob Teague did. I have to buy a new prop either way.

A good top cap and studs will help with the LH stresses. I perfer the XR ribbed top cap and studs. Either way any cap you choose should be measured to accommodate for differences in race shim seat depth. You measure the old cap and the new one from the mounting surface to the area that the shim sits in. Adjust the shim thickness to keep your setup on the gear lash from changing..
Hope that helps.
Dick

Thanks for the replies. Since I have to buy a prop anyway, should I just buy a RH one and forget it?

That depends. If the boat really doesn't like a RH then you are going backwards when you are attempting to go forward to gain performance.
Depending on how many hours are on the drive, if you spin it in the opposite direction, you will be using the other side of the lower gears. If they have started to pit on one side and you spin them opposite, they can fail sooner, because the gears seem to take a set at some point. Seems from experience if you run 200hrs in one direction, then change, you may only get 50hrs out of the other side. It all depends on how much stress the gears have taken prior to switching.
I would go with the LH and add a good top cap (check the shim depths and adjust the shim size) and studs. Keep an eye on your magnets.. any chunks or flakes means the gears are pitting.

Hope that helps..
Dick

Thanks. The drive has 75 hrs on it. I will keep it LH and add a cap.