1984 Evinrude 9.9 over cooling

[Rick.]

Hello. Just replaced the thermostat and gasket due to engine not getting up to temperature. New thermostat didn't make a difference in operating temperature though. Just went over the whole motor carb kit, impeller, leg oil etc. Starts good, runs well but I've only ran in a barrel haven't hooked it up to a boat and run at full throttle. The one thing I'm wondering is if the stat spring was weak would othe water unseat the stat? Putting it together it seamed the spring had lots of tension. I'm at a loss and would appreciate some ideas. The stat is down low in front of the cowl latch and clearance was such an issue I ended up removing the head to remove the water plate. I'm discouraged to think of doing it again. Thank you.

 

[jonesg]

How do you know it runs cold.?
Correct plugs?

 

[racerone]

Is the seal properly installed on the thermostat ??

 

[oldboat1]

Insert the t.stat flange in the gasket slot, which encircles the flange. If you need to go back in, you will likely be able to reuse the head gasket. As you probably found, the two lower bolts remain loose in the head until lifted from the motor. Newer motors (maybe '86 and newer -- but certainly early '90s) have the thermostat at the top of the head, making servicing much easier. You might look around for one of the newer head covers.

I continue to think your cold-running is at least in part due to the cold water in the barrel. Let it idle for 15 or 20 minutes, and it will probably come up to temp. (Monitor so it doesn't overheat.)

 

[Rick.]

Thanks everyone. Yes I'm running the correct plugs. Thermostat gasket isn't the kind that encases the stat flange. Looks more like a garden hose washer and sits against the outer head and the stat and spring sit on top of the gasket. Most I've changed do wrap around the flange but not this one. I've checked the temp. With my hand and an infrared gun. Never came up to heat after twenty minutes at slightly fast idle. The guy I was fixing it up for was in a hurry to get it back so I've asked him to let me know if the temp increases once he runs it at a higher speed for a while.
Appreciate your help/advice. Rick.

 

[oldboat1]

Interesting. I have three 9.9s from '83 to early '90s -- '83 has the slotted gasket, but maybe the '84 doesn't. In any case, I believe the solid gasket goes under the flange on the engine side. Spring sits against the flange on the other "top" side. (looking at a diagram for the '84 from here at iBoats.)

 

[Rick.]

Thanks oldboat1. That is the way I installed, like you said. Many thanks. Rick.

 

[flyingscott]

How cold is.the water in the barrel??? Your motor does not a closed cooling system so water temp has a lot to do with the temp. Not to mention the thermostat mostly controls the head temp because the block has its own drainholes for the water to leave.