Ok, I have a 1998 mercruiser 4.3L v6 with a weber 4 barrell carb with Alpha I gen II drives. I discovered the leaking exhuast manifold by noticing surging of 200-400 rpm while running about 2 weeks ago. I checked all plugs after running and found #6 to have water on the plug.
I pulled the manifolds and they looked terrible. I put a hose to the water intake and after only a few seconds water was coming out of the exhaust passage way like a river. I imagine the hole was huge. I ordered new manifolds and installed them. I also changed the oil twice as there was water in the oil.
When I ran the boat two days ago, I was still seeing alot of surging in the rpm's. I pulled the #6 six plug and it was covered in oil. Now I'm thinking water in that cylinder from the leaking manifold really did this cylinder in. I ran a compression check yesterday but it turned out normal. All six cylinders had 180 psi after going through about 6 or 7 compression cycles. Note: I had to run the compression check when the engine was cold (I had just pulled the riser off the new manifold to try to fish old rubber flappers out of y pipe and the gasket was destroyed upon removal). I did open the choke and had the throttles wide open.
What are your thoughts on this? One more thing. Aside from the surging in rpm's, when I ran the boat two days ago, I was getting alot of backfiring from this engine. Two weeks ago when running the boat, the engine wasn't backfiring at all.
I pulled the manifolds and they looked terrible. I put a hose to the water intake and after only a few seconds water was coming out of the exhaust passage way like a river. I imagine the hole was huge. I ordered new manifolds and installed them. I also changed the oil twice as there was water in the oil.
When I ran the boat two days ago, I was still seeing alot of surging in the rpm's. I pulled the #6 six plug and it was covered in oil. Now I'm thinking water in that cylinder from the leaking manifold really did this cylinder in. I ran a compression check yesterday but it turned out normal. All six cylinders had 180 psi after going through about 6 or 7 compression cycles. Note: I had to run the compression check when the engine was cold (I had just pulled the riser off the new manifold to try to fish old rubber flappers out of y pipe and the gasket was destroyed upon removal). I did open the choke and had the throttles wide open.
What are your thoughts on this? One more thing. Aside from the surging in rpm's, when I ran the boat two days ago, I was getting alot of backfiring from this engine. Two weeks ago when running the boat, the engine wasn't backfiring at all.
