How warm is hot????

[metriccrescentwrench]

'90 Johnson 200.

I found this engine on ebay, had it out for the first time a couple of weeks ago and it overheated after about 10 minutes (water pump was new and water pressure was good).

Neither thermostat seemed to work properly when placed in hot water.
There was a fair amount of crud on the backside of both diaphragms, but what I could see of the water passages in the heads looked ok.

I replaced both thermostats and diaphragms, and thoroughly cleaned the thermostat covers. I ran it on muffs tonight for about 10 minutes, after which the port cylinders and head were warm to the touch but I could hold my hand on them indefinitely. The startboard head and cylinders were significantly hotter, I could only keep the palm of my hand on it for 2 or 3 seconds.

Sooo.... which side is correct?

ALSO... shouldn't there be an orifice or some sort of restriction in the telltale? The telltale hose comes off the top of the port cylinder head and goes directly to a hose fitting in the cowling, there's a LOT of water flowing through there, definitely more than I've seen out of any other outboard. (There's been some redneck engineering done to this engine by one of the previous owners.) Could this be robbing water flow from the starboard side?

 

[oxbeast1210]

Re: How warm is hot????

I always go with the temperature on the starboard because they are higher then the the port side so if water pressure is weak or something is obstructing the water passage the starboard side will overheat first and also get damaged first. I had a similar issue with my outboard my issue was that the starboard water jacket gasket and thermostat gasket had a lot of "Goop" gasket sealer on it and the goop was actually covering some small holes in the gasket that water goes through and some other water passages . This was causing the top right cylinder to overheat , setting off my overheat alarm and making it so i could only touch it for about 2 seconds port side was still pretty cool to the touch so you may have a similar issue

 

[metriccrescentwrench]

Re: How warm is hot????

OK, I was thinking too much, should have checked the basics before developing conspiracy theories about telltale flow. I borrowed an IR pyrometer from work and took the temperature of each head with the engine idling on muffs. Starboard stabilized at around 145 F, port at 112 F - so it wasn't a matter of overheating but rather overcooling. (I had just assumed that there wouldn't be an issue with brand new thermostats. )

I swapped the thermostats and the problem followed the thermostat - now starboard stabilized at 114 F and port at 145 F. Obviously one of the new thermostats is opening way too early.

 

[itsaboattime]

Re: How warm is hot????

I have an '87 Evinrude 110. My starboard side runs hotter than the port side on muffs. I have been told several times that it is normal for the V4's of that era. But on the water both sides run right about the same temp.
You say that the problem followed the thermostat. The thermostats are supposed to open at 140 to 145 degrees.
I would take it out and run it on the water for awhile and then take a temp reading.

 

[ezeke]

Re: How warm is hot????

You might want to check the vernatherms - the temperature rating is stamped on them.

You can test them in water on the stove with a meat thermometer - they should open together at around 140? F.