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I've got a 1983 Evinrude 235 on my 1984 22' Outrage.
On Saturday, I took it for the first time this season (having just completed LOTS of work on the boat, not the engine).
The overheat buzzer went off after about a mile at open throttle. I let it cool down before puttering back to the dock. I removed the port side thermostat and found that the plastic element inside had melted, allowing water to flow through (didn't stop the buzzer from sounding, though).
I'll replace the thermostat, obviously, but here are some other questions that I hope someone has the expertise to comment on.
I'm worried that I may have damaged the rings/cylinders on the port side. Is there a way to check the rings/cylinders without pulling the engine apart?
If the rings/cylinders are OK, I'd like to change the head gasket as a precaution. I'm relatively handy, but the Clymer manual is vague about how to replace these gaskets; is it possible to simply unbolt the head and replace the gaskets without removing the cover and the associated wiring? Any tricks I should be aware of as I attempt this?
Finally, while I'm at it, does anyone think that it would be beneficial while removing the thermostat to inject vinegar or muriatic acid into the water-circulation ports to remove any salt build up?
After the overheat buzzer went off (and after having run open throttle for about 5-10 minutes), I pulled all the plugs (port and starboard) to look at them. At that point, they were all similar, and dry.
After running slowly back to the dock, I pulled them again - now they all (all six cylinders) were similarly lightly wet with oil.
I would perform a cylinder leak down test. It will give you an accurate assessment of the condition of the rings. A leak down test is more accurate that a compression test.
Before attempting any work on an engine, I prefer to use a factory service manual for your peticular engine. If you have a 2-stroke, the head gasket should be pretty straight forward. Be careful removing head bolts as they may be corroded due to salt water.
Kevin
1988 11' Super Sport, 1987 Johnson 15hp.
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