Replacement Atomic 4 Exhaust System
A.J. Matthews #605 Ay Mon
Many if not all of the original (heavy) exhaust systems on our Tritons have long outlived their usefulness. Some have replaced the original systems with costly replacements, while others have fabricated systems from available marine grade components.
When I purchased Ay Mon in 1989, the original system had been replaced with a home made variety out of sections of 1-1/4 and 1/2 inch galvanized iron pipe. That system lasted for nearly five years with the former owner and three additional years under my ownership until one of the nipples rusted through. The beauty of this system is that you can buy replacement parts nearly anywhere and that the total cost of the system (minus the cost of exhaust hose, the Verna Lift Muffler and vented loop) was under $20.00.
My current system has continued to function perfectly for the last seven years. However, I found myself replacing the system while I had the engine out of the boat, with assistance from a member of my faithful crew who makes his living as a plumber. He thought that brass pipe would hold up to the elements better than the iron and gathered the parts at a cost of $50.00. We also investigated using stainless steel (commonly used in Central Florida in the frozen concentrated orange juice industry, available at food processing supply firms), but the cost was much higher at $160.00.
The design of the system is simple, from the exhaust flange, run a loop of pipe up, over and down to the wet exhaust (Verna Lift or similar manufacture). A 1/2" X 2" nipple should be welded into the side of the final 4" (1-1/4) nipple to function as the mixing elbow (if you are using brass fittings, have this union brazed). THIS FITTING SHOULD FACE DOWN AND ABOUT 45 DEGREES TO STARBOARD ON FINAL ASSEMBLY. The 1/2" nipple is then routed back to an area near the rear and above the exhaust manifold then connected with some flexible hose to discharge the raw water from the manifold. If using a fresh water-cooled system, the hose would be led to the discharge of the heat exchanger. To seal the connections, you can use pipe dope or some Teflon tape at each union.
The system is easier to install while it is out of the engine compartment. To accomplish this, assemble the system then screw it into the exhaust flange. REMEMBER TO INSERT THE 5/16 MOUNTING BOLTS INTO THE FLANGE BEFORE FINAL ASSEMBLY. Failure to do so can result in your inability to insert one of the bolts (the "street el" will block full access to the hole). Once the pipe is attached to the flange, mount the flange to the manifold using a fresh gasket and heat tolerant gasket cement, covering both sides of the gasket.
Attach the hoses between the manifold and 1/2" pipe. A vented loop should be installed about 6-8" above the manifold to prevent siphoning. Use a vented loop that will stand up to the hot water being discharged from the manifold. A stainless, bronze or chrome bronze fitting will prove superior. Lastly, attach the hose to the wet muffler.
If you are unable to connect the 1/2" nipple to the 4" down spout by welding or brazing, you can assemble a 1-1/4-tee fitting and use a 1-1/4 to 1/2" reducer to provide a base for the 1/2"x 2" nipple. A 1-1/4 X 1/2" tee can also be used if you can find one. There, you will use a short nipple to the 45 degree elbow and the TEE fitting and a short nipple (2") to the bottom of the tee fitting. While a "TEE fitting can be used, it will make the tail of the exhaust longer. Care must be taken to insure a proper fit between the nipple and the wet muffler.
See the attached diagram and the included photo's for examples.