I have the older aerator system in my X-Star. WAs going to swap out the old pumps with the Tsunamis. Can you mount the Tsunami horizontally or does it have to be vertical for it to prime?

Either way works fine. Vertically, they prime a little better. Depending on the position of the manifold and such, there can be priming issues. <BR> <BR>WIthout knowing your system, I cannot say for sure, but as a general rule, as long as they are below the water line, AND an air bubble cannot get trapped in an elbow or something, then you will be fine. The air bubble trapping can be frustrating if it happens, but usually a simple positioning difference fixes it.

Go with the Mayfair 1000 gph! The screw right into your setup and you will gain 250gph over the tsunamis 750. The Tsunami 1200 are a pain to adapt to stock setups.

duffy makes a good point. <BR> <BR>The Tsunami T800's are great, and the T1200's are better, but have an odd size output diameter. <BR> <BR>Priming issues are the same with any aerator style pump.

The Tsunami T800's are straight threads and will not thread into a std PVC threaded/slip-fit bushing like the Mayfairs will as they are pipe thread.

I have the standard 1100 Mayfairs with th 3/4 output in there now. It takes about 15-20min to fill my 750's back there was tring to get that time cut in half. I figuerd the 1 /18 output tube and the higher GPH would do that for me. The stock system had them mounted to the transom with the intakes coming out the rear of the transom. I was just going to rig the Tsunamis to the same intakes. I thought the Tsunamis were around 2000gph. DOH!