Steam in Exhaust

[Steve C]

Hi All,

I have an early model, circa 1964, running pretty strong. The water jacket exhaust gave up the ghost years ago and was replaced with a Vetus Aqua Lift system. Even after the surgery the exhaust has alway included a fair amount of steam. For many years I ran the engine cold with no thermostat and no recirculation.

One day recently I decided the water exiting the tail pipe seemed to be less than acceptable. I changed the impeller on the water pump, successfully removed the water jacket cooling plate(my hands were black for a week!), replaced the gasket, flushed the engine with muriatic acid, reinstalled the thermostat, replaced the temp. sending unit and the by-pass line. The engine runs at 140 degrees steady and steam still persists. The engine runs very strong and I am wondering what the issue could be.

Should I be worried or not?

Thanks in advance,

Steve C
s/v Juno
San Francisco CA

[Don Moyer]

Steve,

In general, it's not unusual for an early model Atomic 4 to generate a little steam with the exhaust. Depending on the temperature of the water in which you're operating, it doesn't take much incoming raw water to keep the engine cool at low to medium power settings. This leaves a lot of water to simply be recirculated. Since there can't be more water leaving the boat than is coming into the boat, there isn't much water passing out with the exhaust and some of the water is likely to turn to steam as it splashes into the hot section of your exhaust system.

Light to moderate amounts of steam usually do no harm, but if there is a lot of steam being generated, it could convey quite a bit of heat to the rubber exhaust hose which can cause premature failures of the inner liner of the hose.

The reason late model engines don't create steam with their exhaust is because their bypass loop always allows excess cooling water to pass directly to the manifold and out the exhaust. With this bypass type of system, there is always an adequate amount of cooling water passing through the exhaust to cool the hot section sufficiently to prevent steam.

I've often wondered what would happen if someone would connect a small (say 1/4") tubing to the discharge side of the water pump and run it to the rubber water hose just before it connects to the exhaust system. This would provide a small amount of by-passing water (like late model engines) to help cool the exhaust, over and above what is already moving through the exhaust from the engine.

Don

[Steve C]

Don,

Thanks for the info. If I decide to give the extra line from the pump a shot I will let you know how it works.

All the best,
Steve