Can somebody please explain the pros and cons of running water crossovers

Do a quick search and you'll find a million threads on this. Basically, 50% like the circ pumps and 50% prefer the crossovers. Some say circ pumps eliminate hotspots. Other say drill the t-stat with small holes and that fixes it on crossover apps.

I use the crossover with bypass. Drill two 1/8" holes in the thermostat. Looks cool, eliminates another moving part. And it goes way faster and free's up HP. Don't get your hopes up on that last one.

Does it require a two stage sea pump?

no uses same pump

On a stock engine a crossover is a waste of $$$ and will more than likely create problems. They also do not work well on efi's.

mine was already on the boat when I got it, but with no bypass and therm. ran way to cold, changed to a bypass one and therm works great and runs consistant 150 deg. so one less part to fail and freeing up some H/P I like them...Rob