Originally Posted by lazyade
Excellent, thanks. I'm still a bit confused at the previous owner on my boat has but cast iron exhaust manifolds on, which have a a two water fittings at each end, one larger one by the water pump and a smaller one by the transmission. Looking at the diagrams at the above FTP site my boat (half indirect cooling, half raw water) shouldn't have two water take offs from each manifold. Not sure where the smaller diameter take offs go - guess I might see once the engine is back in the boat!
Three scotches to the wind but here it goes: the fittings on your manifold toward the front or the motor should come from your thermostat housing, to send water to cool the exhaust gases. The fittings on the rear of the manifolds, by the transmission are for draining/winterization purposes. I think.