[HellRaZoR004]

This was posted elsewhere and should give you some great idea on how to diagnose the issue.

http://forums.iboats.com/forum/engin...rheating/page2

I have the same set up, only I converted mine to center risers. I still have the block off plate between the riser and the manifolds and the three hose style system as the original log style set up. I would do the following if you know that you have a good outdrive pump:While the engine is running at idle check the water flow through the system on both sides:From T-stat housing to the rear of manifold - if flow is bad, you have a restriction in the block, a bad circulating pump, or a restriction in the T-stat housing. If flow is good move on to the next check point.Flow from the manifold - disconnect the line from the front of the manifold. If flow is bad here you have a clogged manifold and it probably needs replacing or a good cleaning. If flow is good move on the next check point.Flow into the riser - disconnect the line feeding the riser. If flow is bad, you have a stuck closed thermostat or a restriction in the T-stat cover. If flow is good move to next check point.Idle relief ports - located on the side of the outdrive near the transom. If flow here is bad you either have a clogged riser or a stuck exhuast flapper. If flow is good you have to look at the engine internally.Do you have water in the cylinders, water in the oil? It seems as if you have checked all the above, so next I would do a compression check. Also, you might want to do a trick that helped me figure out what I think is my problem. I replaced all the water hoses on the cooling system with clear hose, for diagnositic use only. This way you can monitor flow at all points. I would check for air bubbles in the system. Also, make sure you put a clear hoses on the line coming from the outdrive water pump. If you have air, it could be a bad water pump seal, a loose hose connection on the suction side somewhere, or a leaking head gasket.I had air in my system, and pulled the heads. The gaskets were fine but my block was warped 0.018". The shop said they don't believe it was able to seal. Sorry for the long post, but I could talk for days about what I've done and I am down to the last straw.Hope this helps, good luck!! Keep us posted on your progress.