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Johnson Evinrude Thermostat Replacement

Today's video is about changing the thermostat in a 30 horsepower Johnson outboard and it's proudly sponsored by MarineEngine.com

Johnson Evinrude Thermostat Replacement – Video Transcript

Hey there, Dangar Stu here. Today's video is about changing the thermostat in a 30 horsepower Johnson outboard and it's proudly sponsored by MarineEngine.com.

So the outboard we'll be using for this video is an outboard we've been doing a few other jobs on and it's about a 1994 outboard so this applies to Johnson and Evinrude motors from about that vintage. Alright let's head over to the motor and see we're up against. I had attempt to film two other videos on the weekend that didn't go so well do to parts are needed that I didn't have so this is my third attempt on a Monday so sorry it's running late. Anyway to change this thermostat we need to take this cover off the cylinder head. The water jacket here is held on by quite a few bolts, because of the corrosion here expecting a few of them to give me a bit of trouble. The trick really is just to feel when they start turning easily if not then rather than snapping the bolt try going to some heat etc.

So we'll sort of cross that bridge as we come to it but for now I'll just go and make sure I can get them all turning. There's a few down the bottom here I'm probably not going to get a socket on - I'll probably use a spanner there and here we have a wire going to what I can only presume is some sort of temperature sensor. Looks like the rubbers worn away there I'll take the cover off first and then we'll see where that goes into the head which I presume it does. I did actually finally get around to buy extra Imperial so that'll help get in the bottom one out.

They look about seven sixteenths and I three eighths maybe so it looks like all the ones around the bottom here are seven sixteenths and these top ones are three eighths around the thermostat. Gonna start with a 3/8" bolts feels like that one's going to come okay all three of these felt like that cracks reasonably easily so so far so good. Plenty of corrosion on the threads so I'll clean that up on the wire wheel before you put it back together. This water jacket cover has a torque sequence of putting it back together so what I'm going to do is just start undoing it around the edges then finally under the center just so that we don't sort of warp it on the way off. I don't think it's anywhere near as important to undo it in the sequence that you do it up but we may as well be on the safe side. Because I'm lazy I'm going to use a impact gun to get the bolts out but only once I've tested by hand they are actually coming undone. Sometimes it bolts too if it doesn't feel like it's coming you can actually try and tighten it slightly as well if you can sort of break their corrosion you're halfway.

There all right feels free enough. This hose coming in front of the head here's the tell-tale so I'll just disconnect that just to give it other way comes from the exhaust cover on this side across to the outlet on the other side. As well as not being able to get the impact gun to the lower three bolts. I always find the lower bolts lower spark plug whatever to be the ones that have the most corrosion because I get the most salt water. Most salt here if you only go boating in fresh water you're lucky at least when it comes to maintenance this one is feeling a little bit tighter so I'm just gonna rock it backwards and forwards a little bit all. right Seems like it's cracked I don't have to wind it out by hand. I'll show you this next one once again absolute lowest one absolute worst one so this one's looking pretty here.

What I'm actually going to do is just try and brush the head of it a little bit there's two main things that go wrong one is you round off the head because the socket doesn't sit well enough, the other is we actually snapped the shaft. Both of them are great so I'm gonna clean it up to avoid rounding the head off or else to help with that problem and then we'll see how we go getting it undone. Can't get any sort of power tool in there so I'm just going to use a little stainless Brush.

Okay cleaned up a little better now so let's see how it goes. Beautiful it's coming this is actually a video about changing a thermostat and all about undoing bolts but I reckon with old outboards and this particular style of thermostat where it's under an entire cover it's probably the biggest sob story. Gonna have these issues with the bolts all right lucky last rusty one in the middle feels like it's coming through so we might be in luck today. Actually plan to do a video on stuck and snap bolts and all sorts of corrosion down the track to make sure the perfect outboard for you gonna love it but today looks like we're in luck. I've just disconnected the bullet connector from the temperature sensor to pull the cover off so this is the cover now off here's the spring that retains a thermostat will replace that and the gasket is sitting on the head side here.

Here's the thermostat and straightaway we can see it's stuck open so it's worth replacing. Better to be stuck open than stuck closed but needs replacing anyway. I'm gonna peel this gasket off next I actually don't have a new one of these temperatures which is so I'm gonna leave that in place for now and I'll get one of those and we'll have a look at replacing that later but it's not too bad. That came off in one piece which is good doesn't seem blocked up in any way. It's a bit grubby but the easiest way really is just keep flushing the motor so we'll do that once we've got it up and running. What I will do though is just start cleaning up this gasket surface with a blade you can actually get nice handles for holding these blades I just can't find it at the moment and certainly makes life easier.

Now I'm just going to spray a little bit of brake cleaner and then give it a brush now. I'm just gonna give a very light sand with some 800 grit sandpaper just to get it ready for the new gasket. I'm just gonna give each of the bolt holes a bit of a clean-out with another good option is just to run a tap or a thread chase through the holes but I've only got a metric set so I can't do that but I think that'll be okay. Alright let's look at the cover itself now it's got a few gouge marks here that I can feel quite badly well it looks like maybe somebody's pried it off with a screwdriver in the past came off quite easily this time but what I might do is actually put the whole thing on a brass wire wheel and clean it up.

You can't beat these wire wheels particular in combination with a stone or I guess one of my favorite tools. Alright that looks much better we'll take it to the bench and I'll show you the new bits I got, there's definitely a bit of pitting on this cover but mostly where the water flows not where it presses against their head so we should still get a good seal. Main thing is the new thermostat and spring, sorry but there's the part number for that.

I've also got the new gasket and there's the part number for that I'm going to replace the spring as well but the original probably could just clean up it still feels like I've got quite a bit of strength to it. One thing I didn't get though that it probably should have is the rubber seal that goes around this thermostat so I'm going to try and get this one off and see whether it's still usable. Okay it is soaking water and it cleaned up not too bad ideally I would have ordered one as well I think but we'll live with it. So the service manual for this says to apply OMC sealing gasket compound to both sides of the gasket itself. I don't have that either so I'm just gonna put some Hylomar on both sides.

The manual is quite clear about when the gaskets a supply should be put on dry and when they should have a sealing compound on them and this particular one does require a sealing compound even though I'm gonna use Hylomar for this I am a big believer in using whatever the manual says just because you know better safe than sorry. Quite often they are rebranded products that are very similar to other things so you may be you can do your own homework there but if you're going to order some OMC gasket sealing compounds what you're after just spray this I'm just gonna hang it from a little bit of MIG wire. Spray both sides and let it dry for about 10 minutes before we put it on and then obviously shake whatever it is you're using well. While I'm waiting for the gasket dry it's probably worth showing that this thermostat here is the new one this is the old one, so when they stick open like this it can often be because the motor got too hot.

So it gets so hot for the thermostat actually over extends and gets stuck open so if have you ever motor that overheats it's well worth checking the thermostat. What I'll do now is just put this little rubber washer on the back of the new thermostat so that's ready to install. What I'll do now is take those bolts back over to the wire wheel same thing just clean up the threads on those ready to reinstall. All the threads are cleaned up like this now so ready to install all right we'll head over to the outboard now and start putting this together.

The torque spec for these is 79 Newton meters in the usual. Start the middle and spiral outwards sort of pattern the Imperial sockets I have for a 3/8" ratchet and I don't have a torque wrench that'll do 79 Newton meters until I go down to a quarter inch ratchet. So I'm gonna get some metric sockets that I've got a little fit so I'll use a 10 mil for the 3/8" and 11 mil for the 7/16". I'm just going to clean some of this mud and corrosion out from where the thermostat goes before we put it in then I'll also just do a bit around the lip where that rubber washer goes okay it's not incredible but it's better than it was.

First thing I'll do is just take our new thermostat and then pop that into the cylinder head then going to take the new gasket your sealant on it feed that temperature sensor wire through and just get that in position. Next thing I need to do is take the new spring put it against the thermostat feed the cover over the sensor wire and then compress the spring down on top of the gasket. Now I'm just gonna grab a few bolts the ones for the very top here where my 3/8" bolts I'll just get one of those in get it started then get one of the lower ones started just to hold the gasket and everything in place. Now that I've got a couple of the elevens in lower I'm gonna run these 3/8" down because it's really just the spring pressure coming back pushing the cover off so I might as well get that under control.

First just gonna use a regular ratchet to run them down I'm gonna use the torque wrench to finish them all up. Now I've got these all run down lightly with the ratchet I'm just going to go around with the torque wrench now and do them up to 8 Newton meters. So I'll start with the center now I've got this Center 7/16" bolt tightened up I'm going to start with the top left on here come round then we'll finish up with the three 3/8" bolts.

Reconnect temperature sensor and we're pretty much done so it's a slightly bigger job than it is on other outboards where you have just a separate cover for the thermostat alone but it's not too hard. Definitely say you can do it yourself. Really the keys are be careful not to break bolts by testing them slowly and making sure you clean all the surfaces before you reinstall everything. I wish I'd had a thread chase or a tap to go through those threads I think I could have got more corrosion out than I did. Just by using compressed air and sort of solution the cleaner they are the more accurately torque specs are going to be but I think it's alright.

Alright well sorry this video took a little while to get out because of the false starts out on the weekend but we'll get the parts we need for those and we'll push on with this motor next week. Alright we'll take care catch you soon.