Re: 165 I6 questions
ok, you're all interested so I make this as long as I can.
<br /><br />First, the 'reversed' flow is through the manifold only.<br />Now, the way it 'normally' flows is from the thermo housing into the front of the manifold, to the back, up through the elbow/riser and out the boat, yes?<br /><br />Merc noticed in the late 70's that lots of manifolds were cracking. (see the link to the service bulletin I posted). They determined that the reason for the cracking was that with a boat on the plane the manifold didn't remain full, it would have an air pocket at the front, being the highest point. When the boat was slowed down (came off the plane) it would assume a more 'level' attitude, the manifold would level out also, water would move to fill the air space, but it was very hot (due to no water having been in there when the bow of the boat was higher) and the 'cold' water cracked the cast iron. Easy!<br /><br />Merc came up with a very inventive fix. Run the water from the thermo housing to the
back of the manifold, then forward to the front cover of the manifold, out through a hose to a 90 degree plumbing fitting in the elbow and out the boat. The open exhaust elbow/manifold gasket was replaced with a plate with one small (1/8") hole as an air bleed. <br /><br />I ran with 165 for 8 years before changing to the 4.3. Yes, I had the water reversal kit, and it ran quite nicely. Just a couple of extra hoses on the manifold. I also had the Merc genuine closed cooling kit. Which cooled everything but the manifold.<br /><br />To include the manifold in the closed section wouldn't be all that hard. Just use a completely closed gasket under the elbow, have the water from the thermo housing go to the back of the manifold, the water from the front of the manifold would then go to the 'RETURN' side of the exchanger. The salt water would exit the exchanger and go to the fitting on the elbow and out the boat.<br /><br />There you have it in a nutshell. Ok, it's a big nut!
<br /><br />Chris.............
