Thermostat Johnson 1988 9.9

[timberwolves]

Took the cover off to change the thermostat on my Johnson 1988 9.9 and the old thermostat was broken into pieces. The thermostat seat was also trashed. The old one did not come out easy. It was like it was melted to the head. This motor is new to me and wondering if the motor may have been overheated ? After picking the old seat out in little pieces I replaced the thermostat assembly , as well as water pump, lower unit oil, spark plugs etc. The engine runs smooth and pumps water good.

 

[CMOS]

Did that year Johnson really have the block painted Black, or did the previous owner do that (possibly to hide something?)?


CMOS

 

[Pappy]

Am thinking the 88 model year was a black painted block.

Now...if the engine was overheated you may have more work ahead of you.
You will need to see how warm the engine is getting at or near WOT......without hurting yourself
If it was overheated there is a chance that the grommet at the top of the water tube was melted as well.
Normally when these melt they block overall water flow, which at WOT will create an engine running alot hotter than it was designed to.
If this is the case the engine will eventually seize a piston. You will have a good stream at idle but not enough to maintain cooling at WOT.
You should be able to hold your hand on the top of the block for several seconds at wot. Safety is the first concern here so run it at WOT for a minute or so then quickly drop off plane and shut it off and see. Has to be quick. If you have a digital pyrometer just check the top of the head. No....am not going to tell you what it should be running at....you tell me what the temp is or how long you can hold your hand there.

 

[timberwolves]

Pappy, I don't have a thermometer to tell the temp. However I ran the motor for several minutes not at WOT though, & I was able to keep my hand on the head for over a minute. Taking the valve seat gasket out was a real pain!

 

[Pappy]

From the sound of it I would think you are good to go.
Hey...the seat had only been in there for 27 years!