John E3
Active Member
I have another thread about my engine woes, which ended successfully. In that thear I mentioned that the replacement exhaust manifolds from Mercruiser came with a note saying that drains are no longer required (and missing). I am skeptical.
I started the winterizing process last night, and since I have only replaced 1 set of manifolds/risers/elbows so far, I have a set of BARR manifolds to compare with.
I opened all the provided drain plugs (blue plastic) and drained all the water that was present, on both engines. On the Merc manifolds the hose elbow is conspicuously missing the blue drain, and the 3 port plugs. After opening the other drains on this engine, there was still at least a pint, maybe more that came out of the hose when I removed it. As this is lower than the heat exchanger, I suspect some came from it as well as the manifold. The outboard sides feed the dripless shaft seals, so those manifolds produced no water. Apparently they self drain thru the seals.
After this, I opened the 3 plugs in the Barr manifold and got about 2 cups more water, mostly from the first one I removed, less on the second and almost none on the 3rd. This clearly shows that water is trapped in the lower sections of the manifolds. My worry is that in the Mercruiser manifolds there will be trapped water that could freeze. I'm sure they've tested this "no drain" design for freezing, but it still worries me.
Last season the engine that I did manifolds on was hydrolocked in 1 cylinder (and evidence of water in 5 more cylinders). I had run antifreeze through it for the winter, but as I disassembled it I found pink water in 2 of the drains, but clear water in the other 2. Obviously there was no mixing at that end. I assumed that this was the cause of the hydrolock (freeze crack), but in the end it turned out to be corrosion in the riser blocks that created a 1/4" x 1/2" opening from water to exhaust. They apparently had been leaking for years. Both heads exhaust ports were so badly rusted they were unusable. So, my suspicion of freeze cracks was probably incorrect. I was not able to find any cracks once I got them off. We bought it late the previous season, but it ran fine then.
Anyone have thoughts, or experience, on the "no drain" manifolds? These are the 7.4/454 HO Horizon MPI engines, but I suspect the same design applies to other engines.
I started the winterizing process last night, and since I have only replaced 1 set of manifolds/risers/elbows so far, I have a set of BARR manifolds to compare with.
I opened all the provided drain plugs (blue plastic) and drained all the water that was present, on both engines. On the Merc manifolds the hose elbow is conspicuously missing the blue drain, and the 3 port plugs. After opening the other drains on this engine, there was still at least a pint, maybe more that came out of the hose when I removed it. As this is lower than the heat exchanger, I suspect some came from it as well as the manifold. The outboard sides feed the dripless shaft seals, so those manifolds produced no water. Apparently they self drain thru the seals.
After this, I opened the 3 plugs in the Barr manifold and got about 2 cups more water, mostly from the first one I removed, less on the second and almost none on the 3rd. This clearly shows that water is trapped in the lower sections of the manifolds. My worry is that in the Mercruiser manifolds there will be trapped water that could freeze. I'm sure they've tested this "no drain" design for freezing, but it still worries me.
Last season the engine that I did manifolds on was hydrolocked in 1 cylinder (and evidence of water in 5 more cylinders). I had run antifreeze through it for the winter, but as I disassembled it I found pink water in 2 of the drains, but clear water in the other 2. Obviously there was no mixing at that end. I assumed that this was the cause of the hydrolock (freeze crack), but in the end it turned out to be corrosion in the riser blocks that created a 1/4" x 1/2" opening from water to exhaust. They apparently had been leaking for years. Both heads exhaust ports were so badly rusted they were unusable. So, my suspicion of freeze cracks was probably incorrect. I was not able to find any cracks once I got them off. We bought it late the previous season, but it ran fine then.
Anyone have thoughts, or experience, on the "no drain" manifolds? These are the 7.4/454 HO Horizon MPI engines, but I suspect the same design applies to other engines.
