View Full Version : Smoking engine

11-02-2002, 09:13 PM
" I have a 1977 Mercury 233 (351ci ford) The impeller recently gave out, and I overheated to the point that the engine was knocking. I shut it down immediately, and there was a lot of smoke in the engine compartment. Thermostat showed a little over 200 when I finally looked at it.(obviously too late)

After a tow back to the harbor, and a couple hours to cool down, I managed to drive the boat back on the trailer without incident.

Complete Impeller pump housing, has been replaced, along with the copper tube.

After I got it all back together, Started her up, to test the pump. I still have excessive smoking in the engine compartment, but, oil pressure is still sitting at 60, oil level is correct,and she still sounds very healthy. No knocking grinding or pinging throughout the RPM range. Also, water never came out of the gimbal ring, but I shut her down when the temp gauge got up to about 140 (got scared).

After shutting her down, noticed there was smoke comming from flame arrestor, and in the valve covers (where the oil goes in.) no water in oil, but oil does look and smell burnt. Obviously, an oil change is next on my list.

So, I guess 2 questions, 1. Is burnt out oil enough to cause smoking, or should I be looking for another cause of the smoke, if so, suggestions please. and 2. does the motor have a thermostat on it like a car, that I should replace? "

11-02-2002, 11:24 PM
"Sounds like you caught it in time, but there could still be some residue to be concerned about.

When you do the oil change, take off the valve covers and inspect the heads for coked oil around the the rockers and drain passages. If you see coked oil, plug the drain passages and carefully clean the heads down to the metal. Remove the drain plugs, put some old towels around the heads (to catch oil spatter) and run the engine briefly with the covers off to check for oil flow to all the rockers. Excess heat and detonation can plug or bend pushrods. If any are suspicious, remove and replace them. You may want to check all of them for straightness (roll them on a pane of glass with a feeler gauge) If they all check out, put them back in their original valves, do your lash or preload settings, then reinstall the covers with new gaskets.

If the plugs don't show detonation damage, the internals are probably okay. Watch the oil color and listen to the engine closely over the next few hours of running. The smoking should subside and disappear quickly. Look for any leaks between the heads and manifolds, and excessive blow-by coming out the breather(s) as you run - this can sometimes be mistaken for smoke. And watch your exhaust for smoke.

140 is not to worry about on temp, in fact it's really a minimum for normal running. I'll defer on the thermostat question, but a careful charting of your engine's plumbing should provide the answer. Andrew may have the manual on your engine available here on the site.


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