thermostat on '89 90 hp johnson

brad78

Recruit
Joined
Jan 27, 2003
Messages
5
On an '89 90hp johnson... Do I have to pull the fly-wheel to change the thermostat? Is it under that cover just under the rear side of the fly wheel?
 

Walker

Captain
Joined
Jun 15, 2002
Messages
3,085
Re: thermostat on '89 90 hp johnson

There should be 2 of them and they are either on each head towards the top or they are at the bottom at the rear of the powerhead.
 

ledgefinder

Ensign
Joined
May 2, 2002
Messages
916
Re: thermostat on '89 90 hp johnson

It's #29, but it's not under the flywheel. It's below the exhaust plate at the bottom rear of the engine. There are two of them inside there, one for each bank. They do tend to go bad on this series of engine, stick open, IMHO. I think they are a royal bear to get at. DHadley, who knows a lot better than me, says you CAN remove them without pulling the powerhead. You remove the fasteners on the bottom pan and pull it down as far as you can, and you 'sort of' have access to the three bolts holding the thermostat cover on.
 

Jack Shellac

Lieutenant Commander
Joined
Aug 7, 2002
Messages
1,661
Re: thermostat on '89 90 hp johnson

You can get the thermo housing off using a small open end wrench, but it's a long tedious process since you can only turn the bottom bolts about 1/8 turn at a time. As much as you have to service the thermos on this model, I drilled an access hole in the motor housing on mine just in-line with the bolts. It only has to be big enough for a socket extension to go through. You can put the socket on after sticking the extension through. Then it's a simple job to take the thermo housing off. I cover the holes with a rubber ring-type snap-in grommet. You have to be careful to drill directly behind the bottom bolts or you'll wind up having to enlarge the holes. Of course, this is one of those methods where you have to overcome your reluctance to drill in your motor housing. Use the smallest socket set you can to minimize the size of the hole. I use 1/4" drive.
 

ob

Admiral
Joined
Aug 16, 2002
Messages
6,992
Re: thermostat on '89 90 hp johnson

That's pretty slick Jack. ;)
 

Dhadley

Supreme Mariner
Joined
Feb 4, 2001
Messages
16,978
Re: thermostat on '89 90 hp johnson

I have drilled those holes and then used the rubber grommets from a 1970ish V4 air silencer cover. It worked pretty well.<br /><br />Good luck!
 
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