Logo

Diagnosing a Partially Seized Outboard Motor

In this video I disassemble a partially seized Johnson 40HP outboard to find out why the flywheel isn't turning smoothly.

Dangar Marine

About Dangar Marine

MarineEngine.com proudly sponsors the Dangar Marine YouTube Channel. Our friend Dangar Stu draws on his experience as a commercial boat skipper and mechanic to make some great how-to videos. Dangar Marine videos cover a range of relevant topics in outboard repair, boat repair/upgrades and seamanship. Subscribe on YouTube to be notified when new videos are released.

Diagnosing a Partially Seized Outboard Motor – Video Transcript

Hey there Dangar Stu here. Today's video proudly sponsored by MarineEngine com is about outboards, where you can turn the flywheel sort of halfway then it locks and turn it back, but you can't do a complete rotation on it. So this isn't a particularly uncommon problem and when it does happen, unfortunately, it's generally an indication that the rings are catching on the ports or that a bearing is fouled inside. So, we're going to be pulling an outboard apart - have a look inside and see what's happened in this instance. Before we look at this outboard though I've got another viewer t-shirt photo and this one is Christopher from Virginia in the US, on board his nice vessel. Apparently, Christopher also spent a bit of time on the Hawkesbury so some of the videos are a bit familiar to him.

Alright, let's go and pull this outboard apart and see what's going on with it. In case you're wondering,, this outboard is a Johnson 40 horsepower two-stroke from 1999.First thing I do is just undo a handful of 3/8 fasteners that hold this lower cowling so you can get this off. This outboard already has the airbox and the auto mixing oil to the unit off, so we're not starting from complete scratch. Sorry about that. Because this outboard's already been taken off the boat, it also has things like, four control linkages and the battery cable is disconnected. So far there's been one bolt below the forward latch for the cowling, two below the aft latch and then there is one just here, underneath the powerhead. If you notice water dripping out of that, it's just because I gave it a degrease before I started pulling it apart. Port side lower cowling is off, it's got fuel hoses and things you may need to disconnect, they were already disconnected from taking the airbox off. On this side it looks like all I've really got to worry about is the telltale coming through and then three wires, the red blue and green, for the trim tilt switch on the side. Once you've got those wires off that's it.

Because we're only released in the crankcase and I'm gonna be lifting this off by hand, I'm going to take a few of theses ort of ancillary things off to A make it lighter and B just be get them out of the way. So, I'll start by taking this flywheel off, pulling it off, then I'll pull the whole sort of reed valve carburetor plate off as well. I'm not sure what the nut for the flywheel is on the top, it's probably like an inch and a quarter or something, maybe less. I'm just gonna use a twenty-seven mil socket ... Doesn't sound good, does it? Alright let's say I get a puller onto that and get the flywheel off. You can see here the top of the crankshaft has a depression in it and that's why we're going to use a pointed tip like this on the pullers so it seats into that depression and doesn't slip off. Once we've got the puller in place we're just going to thread some bolts through the puller into these threaded holes in the flywheel. With these bolts that go into the flywheel, it's important not to put them in too far, because you can put them right through the flywheel into the coils and damage those. By the same token, you don't want to go too shallow either because then you won't have enough of the threads into the flywheel and it will just rip the threads out. You're also looking at having them in evenly so that the plane of the puller is absolutely parallel to the flywheel. Otherwise, you'll be trying to pull it up at an angle.

Once I've gotten position I'm just going hand wind the beam until it touches the top of the crankshaft, then after that, I'm just going to put the 19-mil socket on the end of here and just rattle it off. I'm just putting a little bit of spray between the flywheel and the crankshaft just to sort of try and loosen some of that corrosion and quite happy to load this up with a little bit of force and let it sit for a little while. You can use a bit of heat, but once again there's insulated wiring under there and you don't to melt that insulation off the wiring. When you're using a rattle gun you can pretty much just hold the flywheel rather than having to lock it off with a wrench or a bit of wire or whatever but, recommend wearing a glove, because the teeth are sharp and it can start to spit on you. All right so that isn't go so well. It's now tomorrow, the pull-up pulled the thread out of the flywheel the whole lot of it pretty much on one of the bolts, which then sort of bent the others so it was a disaster. Anyway, I knew we were dealing with us today and we drilled and tapped and put a time surge into one of our threads on the flywheel, and then replaced the bent bolts with just some head bolts from an old outboard so they're reasonably high tensile.

Once we put the time surge in we cranked it up with new head bolts and everything and managed to snap one of the head bolts completely in half, just sheared it. Then, put a bit more heat on it which I'm always a little bit reluctant to do with flywheels because the coils underneath... just melting the insulation, but bigger heat seemed to do the trick and finally got it popped off. So, I still left it there and thought we'd pick up tonight. With regards to putting in a time surge, I think it's kind of an interesting process but I am going to do a video that's purely on stuck bolts and I think I'll sort of throw it in as a part of that video on how to get stuck bolts out, maybe how to drill them out if they snap and then how to repair the thread once you've got it out. So, I'll do that as a video in its own right one day. Anyway, so we now have this flywheel off looks like we may have nicked this stator with the drill bit when we were drilling and tapping that thread. Anyway, we'll go ahead and take the stator off, take the carbs off, and get the power head off. The stator here is held on by three bolts that are five sixteenths. I'll disconnect the wires coming from the stator before I lift it off. I think it's unlikely to reach otherwise.

Where possible, I try to put screws back in where they came from, just so you know where they're from and you don't lose them. If I can't do that I always put them in a parts tray. Looks like this black wire goes riding behind everything probably just a ground to the block. But it looks like we have to take all this off to get at it unfortunately. For keeping parts from these sorts of jobs together I actually took one of the old oil containers that we had and just cut the top out and use it as a bit of a holding container for bits and pieces and this works pretty well, saves spending money on anything. Ah good, this whole module looks like it comes off as one piece. She's nice. Thank You Johnson. A couple of HT leads off here from the coils and then one bullet connector here from a enrichment valve, runs up to the solenoid then two coming around for this port side. One of those and the port side. went to the tilt trim motor. This one looks like it might go to the trim sensor and then this is the main loom that went up to the front of the boat, just a few smaller connectors onto the starter solenoid, so that's the starter trigger wires and this is obviously a pickup point for some power. These wires I just took off from the solenoid are feeding power through to the other side, all the metrics on the other side, and that's where the main battery lead would have come into the solenoid as well, so once again a really common place to pick up power in an outboard. Okay stator and electronics in the box.

Next thing I do actually is just take the starter motor off and the starter solenoid. The solenoid's held on with some 3/8 fasteners, The starter itself is held on with some half-inch fasteners. Okay, starter and solenoid in the box. Looks like it's a set of seven sixteenths fasteners that hold this whole, sort of reed valve carb assembly on. Not sure how many of these I'm going to be able to get a gun to, so I might go to a spanner on the ones I can't reach. I also quite like these little wiggle head extensions. They're not like a full universal joint but they do let you just get a little bit of angle on a socket so if you push them on gently they sort of wobble around, and if you push them on all the way, they stay solid so they're pretty cool. Alright I'm going to admit defeat. There's a few fasteners that are too hard to get to with the carburetors on, so I'm gonna take them off separately. I was hoping just to keep it all as one big unit but, c'est la vie. So carburetors off, box is almost full already. I'm just going to get a pry bar now and we'll pry the reed valves off.

This is still feeling reasonably stuck and there's four little screws which I think may be holding it on I'll show you those. So now with all the main bolts out there's screws, flathead screws, here, here, here, and here. So I'm going to take those off and see if they're also holding on. Unfortunately, this particular clip on the video got corrupted on the memory card so I missed a little bit of this video and what happened when I pulled the Reed valves off is I could see a few rollers from the bearings just sort of sitting in the crank case down at the bottom. I managed to fish those out and so we're pretty sure now that it's some sort of bearing failure. Unfortunately, though I didn't get that bit of the recording captured properly so we'll push on from there but that's really what I found when I took those Reed valves off. The next thing I'm going to do is take this rotatable Ignition coil off, which is held on by some flathead screws. The screws just hold on these little locking tabs. Underneath there is some little 5/16 fasteners that just hold this plate on. There are three fasteners under the power head on each side, which are 1/2 inch, so I'm going to take all those out and then we should be able to lift the powerhead off.

These bolts are a bit rusty and I'm actually having more luck with a 12-millimeter socket which is slightly smaller. Once again, not sure if that's what they actually are or whether it's just that they've rusted down to. Nah, I think it's what they've rusted down to because the ones in better condition it doesn't fit on. This is the stuff you get in thread that makes these bolts so much fun to get out. Of course, this last bolt's not coming out now. I was using a six-sided impact socket which is normally pretty good, the 12 sides don't get the same grip, but even still it's just slipped to end up rounding this rusted bolt off. You actually had quite a lot of impacting motion on this initially and it still wasn't budging at all. What I'm going to do now is disconnect the shift linkage and then just split the crank case with the power head still attached to the link. The shift linkage attaches up here and there's just a 10-mil fastener holding it on. What I'm going to do next is take the spark plugs out. The reason we do that is because we're going to be splitting the crank case with the motor attached, then pulling the Pistons out through the bottom of the crank case, and this will just make it a bit easier to do as I won't have any compression happening inside the cylinders.

Spark plugs look reasonably equal. I've taken off the smaller crank case bolts around the outside now we've just got a few larger ones on the end caps to the bearings, so we'll pull these out, and then try and separate the case. There were six of these larger bolts aloft, looks like the center ones are a bit shorter. The last thing you need to get is just a couple of fasteners under here at the top of the pivot arm they're heading upwards. You can see here it's just starting to separate a little bit so I might see if I can get something in here. You don't really want to damage these surfaces because if we put it back together, assuming this is worth repairing, you're going to want these surfaces to still seal well. Seems to be coming off pretty easily, which is nice. Small bits of metal, more bits of metal. definitely finding more bits of bearing cage and rollers. There's also quite a deep score in the case along here. Next thing I'm gonna do is take the gearbox off so the drive shaft comes out from the crankshaft, so we can pull the crankshaft out. This gearbox is pretty stuck on. The drive shaft top is a bit corroded into the powerhead. Normally, or it's always a bit of a tricky situation, and I do get asked a lot of questions about this one.

Normally you can't get any heat up there but because we've got the bottom of the crankcase off, we can. So I'm going to go and put a bit of heat at the top of the drive shaft and see if that helps release it. Under here is the bottom of the crank shaft and the top of the drive shaft, so this is where I'm going to put a bit of heat Obviously, this rubber seal's a bit worse for wear, but big deal. It looks like the bottom of this oil seal housing also has more of these fasteners up into the engine block itself, so I don't think we'll be able to pull it off without removing the engine block. Which means, cutting out that bolt that's not coming out. I'm just going to have a go at cutting their head of the bolt off, then hopefully we'll be able to pull the power head off and pull the shank of the bolt all the way through. It might be tight as well but I think it's the best shot we've got so far. We'll see how we go lifting off now I'm actually kind of glad we took the gearbox off now I think about it, because having that stuck drive shaft was only going to be extra force to fight against.

We've still got the shafts two bolts in here to fight against as it is. Looks like there's another nut I have to get off a stud here as well. I think the best we can do now is hook the powerhead up to a crane, lift it, and then probably hammer down on the leg to try and separate them. I'm going to put some heat all around the base here and see if we can get that base to expand away from the remaining bolt shafts a little bit. I think it's pretty obvious what's going wrong here. I'm gonna get a beer. I'm going to try to get a pin on to the end of the bolt that I cut the head off and try and punch it out. That went absolutely nowhere so I'm going to try putting an air chisel on the top of the bolt. This is going nowhere in a hurry, going to try a lot more heat. Powerhead's off. I didn't film it because you really didn't need to see my cranky face as I hit that as hard as I could with a large hammer. I ended up driving a wedge under it, under the leg in the powerhead. Those two bolts that went through broke again, in the second place, that's how stuck they were. If you haven't figured it out already this motor sunk a while ago, hence all these corrosion problems. It's also lived in 20 years in salt water when being used before it even sunk.

So, I'm not thinking this is worth repairing so this date it's about pulling it apart to show you what's going on. This is often a thing with old outboards. Something fails, like bearings in this case, but the rest of the Apple is in such corroded condition that by the time you get it apart, if you can, more damage will happen, you'll spend money machining it, you then buy all the gaskets and everything to put it back together and it just easily exceeds the value of the motor. That's really where we're at with this outboard now. But we've come this far so let's get this crankshaft out and show you what's actually failed, which is kind of the point of this video, because it is quite common particularly for two strokes to have this symptom, and this will give an idea if you have this symptom, what you're gonna be up against. Now we can get to these last two bolts that we couldn't get to, all the powerhead was on. Next thing I do is get the end caps off the con rod so we can pull the crankshaft out. So far that bearing was in one piece this one not, though, so the big end bearing for this lower piston is the one that completely failed. Here's more of the cage, more rollers. We'll get that out with the piston from the other side.

So, there's our crankshaft, a bit of damage to the journal from when those damaged rollers were coming around, so you need to get that machined as well. There's more bits of metal that have been rattling around in the motor while it was running. All right, let's take the head off and pull the pistons out. Not to do damage here, I can't get a socket on so, I'm just going to file it flat again. These are the rollers hitting the top of the head as they bounced around the engine. That's the top of the piston, where all those rollers have been hitting. There's a few completely embedded in the top of the piston. So I don't care what Aaron tells you, bearing failure is not your friend. Is this motor repairable, yes, you saw what we did with the Evinrude before, same style of motor, same end caps etc but the cost of this motor just doesn't justify it. Not to mention drilling out those snap bolts, it's just well out of the realm of what it's worth.

So at least we know. We know what's wrong with it, we kind of knew what was wrong with it to be honest with you because whenever you have an outboard flywheel that turns, a little bit catches, it's quite free until it catches, it's always some sort of bearing failure like this. It can be a ring catching on one of the ports, but in my experience, it's more likely to be bearings. So, if you have that symptom, you kind of know what you're up against. It's up to you then I think. Whether you look at the value of the Motor, if it's reasonably new, been used in fresh water for whatever reason you had a bit of a freakish bearing failure, it's worth fixing up. You know, go for it. But if it's an older model like this, just be aware and you're probably up for a new head, new Pistons, machining, machining the crank shaft, seals, all the labor. Probably better off getting rid of it. Alright well that's it for today and I know it wasn't a very cheery video, sorry, but this does happen you know and you can tell from the outside quite quickly what's going on most of time. So, I just thought I'd let you know, that if you're having this symptom, this is what you can expect. All right, well take care. I hope you never end up with this happening to your motor, and I'll see you next week. Bye