How much steam is too much?

[scotsman60]

Hello!!!

I'm a newbiew Atomic 4 owner and this is my first post.

I recently acquired a Peterson 30 with a late model Atomic 4 installed. The motor is raw water cooled and had some difficulty starting.

I changed the distributor cap, points, condenser and plugs and reset the dwell. I also carried out an acid flush and replaced all of the cooling system hoses, and installed a new thermostat (none installed when I got the motor) and cleaned out the raw water strainer.

The motor now starts first turn but I'm getting some steam in the exhaust. At low idle (~500rpm), the temp goes to 150 on the guage (140 using a thermocouple on the head surface next to the temp sensor). There's not a lot of steam (wisps) and what appears to be plenty of water in the exhuast. If I increase the idle to 1500 the temp increases to 160 the steam increases to a steady flow and the volume of water remains more or less the same as at low idle.

I'm concerned about the steam. Is a certain amount of steam normal at idle? If not, what are the likely causes? I'm ordering a new water pump today just in case but I don't think this is the root problem.

Is a head gasket leak likely? - water getting in to the cyclinder could be causing the steam but I'm not seeing any signs of this on the plugs. Compression is on the low side (95 psi with cold engine and the plugs loose but not removed).

Is a cracked manifold likely? Water leaking into the exhaust manfold could produce steam.

Any ideas and help will be gratefully received at this point. I'm wary about taking the boat anywhere at this time due to the steaming problem.




Doug

[Administrator]

It is first necessary to clarify the difference between steam and white smoke. White smoke will linger behind the boat for several boat lengths, while steam will dissipate quickly - normally within 5 to 10 feet. White smoke is almost always caused by oil entering the combustion chambers and burning along with the fuel mixture. Steam will normally be caused by one of the following conditions:

1) In the cool part of the season, it's rather common within our northern operation locations, for people to report a "vapor" coming out with the exhaust on their boats. This vapor is simply a matter of warm moist air cooling and condensing behind the boat. The problem goes away as soon as the weather warms up a bit.

2) Early model cooling systems will create a small amount of steam until the engine gets fully warmed up. While an early model engine is still cool, most of the cooling water is being recirculated, leaving an insufficient amount of engine cooling water is be discharged into the exhaust system to cool the hot section, and what water does enter the exhaust system turns to steam. As soon as the engine warms up, more water will be discharged to cool the exhaust system, and the steam should dissipate.

3) In both early and late model engines, cooling water flow may have reduced, due to a defective water pump or a restriction in one of the cooling hoses, so that there is no longer sufficient water flowing through the engine to keep the hot section of the exhaust system cool, and a small amount of steam may be developing in the part of the hot section where the engine cooling water enters the system.

4) Steam will sometimes be created as the hot section slowly clogs with precipitate where the engine cooling water enters the hot section, usually just above the inlet to the water lift muffler.

NOTE: In both (2) and (3) above, the creation of steam may be somewhat exacerbated if the hot section was recently wrapped with an insulating material, since the insulating material will result in a hotter temperature
within the hot section.

5) The most serious scenario would be steam caused by a small amount of water leaking into the exhaust manifold through a crack in the block, head, or manifold itself. Steam created by a small crack in one of these cooling water jackets will usually elevate exhaust back pressure within the manifold or the rest of the exhaust system, which will - in turn - cause a very thick caramelized brown goo to form on the stems of intake valves. We have several cases on record where intake valves have stuck open in only 5 to 10 hours of operation.

Don

[scotsman60]

Don,


Thanks for the reply.

1) I'm in Newport Beach, California and I'm seeing this behavior when the air temp is in excess of 80 degrees so I think we can discount warm moist air as the cuplrit.

2) I have a late model engine and I get a lot of flow to cool the exhaust as soon the engine runs. In addition, the condition persists even when the engine has fully warmed up so I don't think this is the problem.

3) I don't know what a normal amount of flow is for this engine so it's possible that I'm not getting enough flow to keep the hot section cool. I get a healthy pulse of water out the exhaustevery couple of seconds and I felt that was OK - what kind of flow should I be looking for?

4) I pulled the hot section pof the exhaust and the muffler last night and both look good - no restrictions or clogging.

5) I inspected the valve stems last night - they look to be in pretty good condition - no brown caramelized goo.


I also pulled the head last night and, using a stiff coat hanger wire, scraped quite a lot of ruts/scale flakes out of the cooling passages. I then flushed the head water passages with muriatic acid and got them pretty clean. Given the amount of stuff that came out I suspect that this may have been part of the problem.

Today I'm going to give the block the same treatment - the engine is still in the boat so it's not so easy to access as the head was on the bench.... I should receive my new water pump today so hopefully when I put it all back together the problem will have been cured.

I'll report back when the engine is running.




Doug

[scotsman60]

Update

Here's an update on my exhaust steam problems.

After removing the head and cleaning the waterways with a coat hanger and muriatic acid I cleaned out the block waterways the same way.

I put the head back on and installed the new water pump and the new thermostat. I also did a valve adjust.

The motor started right up and ran smoothy at idle - I have no exhasut steam at idle. Under sustained load I do get a little bit of steam in the exhaust - no more than a wisp - and it remains constant even after sustained running for a couple of hours. Engine temp under sustained load is about 165 Fahrenheit according to the gauge.

I'm kind of surprised that I have any steam at all, however I'm pretty comfortable that the engine will run reliably without overheating so I'm going to stop worrying about it for now and just keep an eye on things.




Doug