See full version: How to Change the Thermostat on My Evinrude Outboard
Use a screwdriver to remove the three small screws that hold the cover onto the valve body. Pull out the springs, thermostats, relief valves and all grommets with your fingers (or pliers if they are stuck) and discard them. Clean any corrosion from the valve body with emery cloth or fine sandpaper, particularly if the engine has been operated in salt water. here
Emery cloth or fine sandpaper more
Install new grommets into the valve body. Install the two new relief valves into the grommets (the smaller, shorter side of the relief valve should face away from the grommet). Position each new thermostat into the valve body, with the temperature-sensing end pointing into the valve body. Insert the new relief valve springs into the bores in the housing. here
Coat the outside of the valve body and a new gasket with gasket sealing compound. Put the gasket in place and replace the cover onto the valve body. Install the valve body into the adapter housing, making sure that the relief valves fit into the relief valve springs. Secure the valve body in place with the three screws.
Outboard motors require a flow of cooling water to maintain proper operating temperature. At high speeds maximum cooling is needed to prevent engine damage while at idle the engine must stay warm enough to avoid fouling the spark plugs. The thermostat maintains the correct temperature. The constant flow of water through the thermostat means that it should be replaced regularly. The Evinrude V4 cross-flow engine uses two thermostats, one for each cylinder head.
Anyone know if I can replace it with a "modern" one?
There doesn't appear to be a spring. more
In a bucket of water, she started today on the second pull and ran sweetly, with plenty of cooling water, lovely tick over and smooth response across the rev range. However, the cylinder head covers (and rest of engine) didn't get beyond lukewarm. What's more, if I increased revs, the covers actually cooled down to almost chilly and stayed there. I figured that the thermostat might be stuck open, so I took the cover off to reveal what you'll see in the photos.
Around the top of the thermostat is a deformed piece of plastic, that appears to have partially melted and started to flow in the direction of the water channel. In fact, it had moulded to the shape of the channel and it took a bit of "persuading" to come out. more
Today I started my Mariner 6Hp 2 stroke for the first time. The motor came with my trailer sailer but, in the 4 years I've had the boat, I've never used the motor (Rutland is electrics-only for us sailors).
I did my due diligence on the fuel tank, filter, impeller and gearbox oil. The carb and thermostat I took on risk.