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  #1   IP: 75.69.110.251
Old 08-14-2010, 08:20 AM
Irwin30 Irwin30 is offline
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Intake/Exhaust Manifold

I wanted to share with you all a problem I came up against regarding the intake/exhaust manifold on my A4.

Last summer I was having an extremely hard time starting my A4. After much fussing, I was able to get it started, but noticed , if you can believe this, when I removed the #4 spark plug while the engine was running, that cylinder was blowing water. The result was water everywhere. Most noticeably water in the carb, and in the oil. Amazingly, the motor would run, although it clearly was taking in water from somewhere. After resurfacing the head and replacing the head gaskets, to no avail, I resigned to the theory that I had a cracked cylinder wall, and began my search for a replacement motor.

Fast forward to this summer. I stripped my old A4 of most of the parts and moved them over to the replacement motor I procured last fall, thanks to Craiglslist. After a few setbacks with rusted bolts and rotted gaskets, and engine timing, I had the new motor running like a top in my garage, before I transplanted it back into the boat. I was, however, a little concerned with some signs of water dripping out between the block and the intake/exhaust manifold, so I decided to investigate. At first it looked like simply a bad gasket seal, but as I delved deeper, I discovered a much more disturbing problem existed. I decided to hook up some hoses to the water fittings and test the water flow through the manifold in my basement sink. To my amazement when I applied pressure with my thumb to the hose, where the water was exiting, I began to see water entering the intake side of the manifold. This side is of course, where the gas from the carburetor, enters the cylinders through the valves. Somehow and somewhere, there was a crack in the manifold, allowing water into the intake ports.

Because, my old manifold had all the fittings for my exhaust system, and the manifold that came with the replacement engine did not, it seemed easier to just swap them out, than rebuild the exhaust fittings. If I had not tested the manifold, I would have been right back to where I started last summer. In fact, if I had 20/20 hindsight vision, I could have probably just replaced the manifold on the old motor, and saved hours of aggravation, and hundreds of dollars. But then I would have missed out on all the fun of troubleshooting an Atomic 4. I personally have a Love/Hate relationship with them. I love that they are so simple to work on, but hate that I need to work on them. Still, I refuse to breakdown and go Diesel, like so many of my fellow boaters near me have decided to do. Thanks to Moyer Marine, we have an invaluable resource for parts, and expertise on these mystifying engines. I hope this post saves someone else some of the grief I went through. I don’t recall of hearing about this exact problem through this forum, but I do seem to come across the bizarre and rare problems with these motors. Maybe another day, I will share my experience of breaking a crankshaft in an Atomic 4.

Off to the boat, for my first sail of the season (on August 14th) .
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  #2   IP: 173.166.26.241
Old 08-14-2010, 09:08 PM
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hanleyclifford hanleyclifford is offline
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Irwin 30 and all - I too have experienced the internal failure of a manifold. It is important to do a pressure check of any suspect or new (to you) manifold.
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  #3   IP: 206.125.176.3
Old 08-16-2010, 08:50 AM
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sastanley sastanley is offline
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Irwin 30 - I only beat you by one week (I launched August 4).

Mine was not specifically motor related, but it was a worn/rotten shaft tube, which led to new stuffing box, shaft, cutless bearing, couplers, alignment, etc.etc.etc..

Thanks for sharing your experience...You could not have written your love/hate description any better!
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"Holiday" - '89 Alura 35 #109
"Twice Around" - '77 C-30, #511 with original A-4 & MMI manifold - SOLD! (no longer a two boat owner!!)
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