I recently acquired a 74 Newport 30. The original owner kept the boat pretty much as it came from the factory down to the vintage avocado cushions and yellow bubble glass sliders on the galley compartments. No upgrades, no modifications. As you would expect, the boat needs some TLC and a lot of cosmetic attention. The original Atomic 4 still ran!!!
The boat had been left on the pier for three years before I got it with nothing done to it so I was very surprised to get the thing cranked at all. It had some fairly pronounced valve taping and after several weeks of Marvel Mystery Oil, It seemed to quiet down. At first, She was very hard to start so I rebuilt the carb (which was so full of goo that I couldn't imagine how it ran at all) and pulled the plugs and found them all to be very fouled. New set of plugs, rebuilt carb. and more Mystery oil treatment and she cranked right up. I was surprised that I didn't have to replace points and condenser but it started fine after about three seconds of cranking.
She ran fine for the first outing but the next day it was back to the hard starting again. I pulled the plugs and found them to be just as fouled as the old ones I had just replaced. I decided to get the hotter Autolite plugs and see if that would help. Nope!! Still fouled.
So, after much reading and thread chasing I decided that I had a back pressure problem. As I said before, this boat is vintage, no upgrades so the exhaust system was all original (new hoses being the exception).
The hot pipe exits the manifold above the waterline in my boat and turns to port and down to meet the bottom of the old copper muffler below the waterline. The cooling water runs from the back of the manifold to the TOP of the copper muffler and I assume showers and cools the exhaust. The main exhaust hose leaves the BOTTOM of the muffler and carries the water and exhaust to the transom.
This system all looked to be in good shape and had (I assumed) served the previous owner well for many years. I thought it was odd though that he would keep such a large stash of plugs on board.
Anyway, The exhaust and cooling water seemed to exit the transom as it should so I figured I had some blockage somewhere. I wasn't quite ready to tackle replacing the hot pipe or the manifold just yet so I continued reading. The exhaust pipe dipped down after it left muffler and then rose to meet the exhaust port at the transom. My first thought was that this was normal because it must have come from the factory that way. Nothing else on the boat had been changed. BUT....I was still fouling plugs and I couldn't find my system explained or pictured or discussed anywhere so I didn't know if it was correct. I was starting to wonder if it had been installed that way or was this the only modification the PO had made. It didn't follow the logic of any system I could find. It all seemed to be too far below the waterline and hold too much water in the downward bow of the pipe. The exhaust had to push a lot of water out of a long uphill tube.
I decided to try to emulate the configuration of the exhaust pipe on the water lift muffler and raise it above the water line as soon at it left the muffler. I raised the exhaust pipe as high as I could just as it left the muffler and let it fall the rest of the way to the transom. I probably raised it a good 18 inches and the rest of the pipe drained naturally to the exhaust port. I figured it was holding at least a quart of water in there before I raised it.
I started her up and she immediately ran smoother and much to my surprise, I have not had one fouled plug since. I pull them frequently to check and to continue my Marvel Mystery oil treatment and they continue to be dry and toasty looking. Just that little bit of back pressure relief changed the way she ran that much! I still can't believe this old engine runs as good as it does after all these years. If only the PO had figured that out years ago. I imagine him going through plugs every outing.
I was able to find a diagram of my particular installation on-line and I will try to attach it. I have still not been able to identify my muffler but it still works and even better now.
The boat had been left on the pier for three years before I got it with nothing done to it so I was very surprised to get the thing cranked at all. It had some fairly pronounced valve taping and after several weeks of Marvel Mystery Oil, It seemed to quiet down. At first, She was very hard to start so I rebuilt the carb (which was so full of goo that I couldn't imagine how it ran at all) and pulled the plugs and found them all to be very fouled. New set of plugs, rebuilt carb. and more Mystery oil treatment and she cranked right up. I was surprised that I didn't have to replace points and condenser but it started fine after about three seconds of cranking.
She ran fine for the first outing but the next day it was back to the hard starting again. I pulled the plugs and found them to be just as fouled as the old ones I had just replaced. I decided to get the hotter Autolite plugs and see if that would help. Nope!! Still fouled.
So, after much reading and thread chasing I decided that I had a back pressure problem. As I said before, this boat is vintage, no upgrades so the exhaust system was all original (new hoses being the exception).
The hot pipe exits the manifold above the waterline in my boat and turns to port and down to meet the bottom of the old copper muffler below the waterline. The cooling water runs from the back of the manifold to the TOP of the copper muffler and I assume showers and cools the exhaust. The main exhaust hose leaves the BOTTOM of the muffler and carries the water and exhaust to the transom.
This system all looked to be in good shape and had (I assumed) served the previous owner well for many years. I thought it was odd though that he would keep such a large stash of plugs on board.
Anyway, The exhaust and cooling water seemed to exit the transom as it should so I figured I had some blockage somewhere. I wasn't quite ready to tackle replacing the hot pipe or the manifold just yet so I continued reading. The exhaust pipe dipped down after it left muffler and then rose to meet the exhaust port at the transom. My first thought was that this was normal because it must have come from the factory that way. Nothing else on the boat had been changed. BUT....I was still fouling plugs and I couldn't find my system explained or pictured or discussed anywhere so I didn't know if it was correct. I was starting to wonder if it had been installed that way or was this the only modification the PO had made. It didn't follow the logic of any system I could find. It all seemed to be too far below the waterline and hold too much water in the downward bow of the pipe. The exhaust had to push a lot of water out of a long uphill tube.
I decided to try to emulate the configuration of the exhaust pipe on the water lift muffler and raise it above the water line as soon at it left the muffler. I raised the exhaust pipe as high as I could just as it left the muffler and let it fall the rest of the way to the transom. I probably raised it a good 18 inches and the rest of the pipe drained naturally to the exhaust port. I figured it was holding at least a quart of water in there before I raised it.
I started her up and she immediately ran smoother and much to my surprise, I have not had one fouled plug since. I pull them frequently to check and to continue my Marvel Mystery oil treatment and they continue to be dry and toasty looking. Just that little bit of back pressure relief changed the way she ran that much! I still can't believe this old engine runs as good as it does after all these years. If only the PO had figured that out years ago. I imagine him going through plugs every outing.
I was able to find a diagram of my particular installation on-line and I will try to attach it. I have still not been able to identify my muffler but it still works and even better now.
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