Johnson 55hp thermostat/valve grommet/pressure relief valve/cover to head gasket

Hey guys, I just tore into my thermostat on the 1983 johnson 50hp. I have never messed with a thermostat before. I am not familiar with the valve grommet and pressure relief valve. Is this what you call a "poppet"? Just wanting to know if simply replacing the thermostat is adequate or if I need to replace some of those other things while I am in there. Can I just use some formagasket when reinstalling or do I really need to order the proper gasket? Also is it normal for there to be some flaky stuff/tiny rocky things behind the pressure relief valve?

Re: Johnson 55hp thermostat/valve grommet/pressure relief valve/cover to head gasket

Yes, you need a gasket, and coat both sides with gasket sealing compound. I would replace the poppet valve while im in there, it isnt too expensive, and why not while you;re in there. The corrosion you speak of is normal, try to clean the scale as best you can.

Re: Johnson 55hp thermostat/valve grommet/pressure relief valve/cover to head gasket

when i go in i replace everything. why go back?

Re: Johnson 55hp thermostat/valve grommet/pressure relief valve/cover to head gasket

so the poppet is also refered to as the pressure relief valve? Do I need the valve and the grommet? Also, is the temp sensor wired in a way that my motor will make a sound or shut off if it gets too hot, or is it simply a thing for a temp gauge?

Re: Johnson 55hp thermostat/valve grommet/pressure relief valve/cover to head gasket

could someone give me a rundown of how they usually do this process. I just want to do it right, and not have to do it again. Ok, get all new pieces, and new gasket and some sealer. Can this sealer be purchased at the auto parts store? Is there a product that I can use to make sure all of the old gasket comes off, can I simply soak the old gasket with water and scrape it off? And can someone tell me what the poppet actually does and how the thermostat and all of that works together. Thanks guys, I am trying to learn this hobby of mine.

Re: Johnson 55hp thermostat/valve grommet/pressure relief valve/cover to head gasket

I have never had an old gasket give me much of a problem, nothing a razor scraper wont get off. Most auto parts stores around me carry the gasket sealing compound that you will need, or your nearest BRP dealer/mechanic will carry it.

The pressure and temp controlled cooling system contains the pressure valves (poppet), springs, and t stats. The circulation of water through the cooling system by the water pump (impeller) is controlled by the balanced action between the pressure control valves, water pump pressure and the t stats. When the power head and cooling system temps reach around 145 F, the t stats open, allowing heated water to pass through the water discharge. As engine speed is increased, water pump pressure opens the relief valves. This bypasses the t stats, allowing the engine to run cooler when it is running at higher speeds.

The service of the t stat is easy. Remove the four screws. Tap the t stat cover lightly to break the old gasket sealer, and remove the cover. Remove gasket and t stat, o ring, spring, and pressure valve. Throw out the old gasket and o ring. If the grommet under the cylinder head cover has deteriorated, remove the cylinder head cover and gasket. Thoroughally clean surfaces, and replace with new t stat and pressure valve.