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.