Thanks Tunahelper, just had a look at those....so are you running a heat exchanger or raw water?
A dog clutch is an in or out transmission that's run off the timing cover end....you can select it in at 500rpm or less and it goes in with a crunch and then you're off. I've never used one but they are very common in Oz with ski boats. I haven't heard of them in the States so i'm guessing they're not so common? The one i've used is made by an Australian company called Kincaid Marine Rolco
http://www.kmrolco.comThey're straightforward to install...they bolt on where the timing cover did and you slide on what's called a "nose dog" which has a keyway onto the crank and a set screw....you then drill in and insert a pin to also keep it there. A lever on the housing then meshes the two dogs together to engage it or pulls them apart for neutral.
I'll pop some photos up of it. If you want dimensions let me know and I'll post them up.
Marcus