First off, what's the intended use of the boat? Based on the pic, I'm guessing cruising around and maybe some skiing or tubing. A family boat, correct?
I am no expert on this by any means. But, the JF is an insert type pump, and switching to a JC or JG pump would be a very involved process, requiring lots of glass work, thus lots of money. If you don't like the JF it would probably be cheaper to find a different hull with a JC or JG pump. But there is nothing wrong with the JF pump, the boat will be a great cruiser and family boat. Should move along quite well with the horsepower you're putting to it, should be great for skiing and such. You should have plenty of fun with it, but don't expect to be able to race anybody.
The valve near the pump is not a necessity, but it is cheap insurance, and adds a bit of adjustability to the system. If you blow a water hose, you can shut the valve, and prevent your boat from sinking. But if you add a valve, you really need to put a pressure gauge on the system, so you know what the water pressure is coming out of the pump. If you don't have a gauge and you adjust the valve, then you have no idea what effect you're having, and could possibly cause damage to something. I just use a simple gate valve attached to a piece of copper pipe threaded into the pump, then it's all hose from there. But I have headers and a JC pump, and you have logs and a JF, so the plumbing is a bit different. But I would still put a gate valve on there, might cost ya $15 for the valve and any fittings required, but it might keep you from sinking the boat someday.
Good luck and most importantly......have fun!!!
