Need help bringing a Johnson 20R273A back to life

My bad but his worse. Really should have had him call me when he put the pontoon into the water. I also rebuilt the motor mount for him when I repaired the literally "melted" outboard. Used marine plywood, polyurethane, did a beautiful job. Wanted to gain his respect but he probably didn't appreciate it. Never heard from him again until I called him later in the summer and he said everything was working beautifully. That was 4 years ago.

Speaking of seized motors...I may have just seized mine. Im currently letting it (and me) cool down.

So I took off the lower unit today a few times attempting to get it pumping water. I checked several things. Made sure that the water tube was inserted into the impeller housing and that the rubber grommet was in place. Checked that the impeller vanes were oriented the correct way and that the impeller key was in place. Checked that the passageways weren't blocked by poking into them with a coat hanger and blowing through with air. Took off the metal cover on the side of the lower unit which I assume is a water inlet to make sure that wasn't blocked. Made sure the water level in the tank was all the way to the joint where the lower unit attaches to the leg. Ran it briefly with the thermostat and cover removed to see if maybe it was just the pee hole blocked. No water came out of the thermostat housing.

After all that I disassembled the impeller housing again. Noticed that the plate that the impeller sits on wasn't oriented the way it is in the parts drawing. There's a little semi circle cutout in the plate that I assume is a water passage. Mine was oriented to the front and it was oriented to the port side in the parts drawing. I flipped it to match the drawing and then reassembled everything.

When I started the motor it started pumping water out the pee hole after about 3 seconds. Having confirmed that it was peeing, I started tinkering with the idle stop screw and then the low speed needle. I looked down and noticed that it was no longer peeing and then it stalled and hard stopped with a ringing noise. I disconnected the plug wires and tried pulling on the starter rope and it feels seized. At that point I put down my tools, came into the house and got a beer out of the fridge.

Not sure where to go from here. Any thoughts?

Took the recoil starter off and attempted to move the flywheel by hand gently. I can rock it back and forth a few degrees but definitely seized.

Which motor is it? The one that you just bought? Or the one that had gone swimming? Sorry I'm thinking of another post.

I'm gonna review this post and see what's gone wrong.

This one is the only one I have. I know almost nothing about it's history but doesn't appear to have been submerged based on lack of rust in the internals.

Thanks Timguy. Im sure it's hard to keep them all straight when you're helping multiple people. Pretty sure I overheated it due to lack of water flow.

Right....first I gotta say, I am so sorry but how could it have overheated while you were working on it? When they overheat the motor just s l o w s to a stop, they just don't go "clink". Did it feel hot to the touch. Should run about 150 degrees. Maybe something happened in the lower unit. Try removing it again and see if that is your problem. Gotta check the water pump anyway. Maybe you didn't have enough water in your test tank. If you can take a picture with that smart phone, show me exactly what the water level was on the lower unit/leg area. You will need to reduce the photo file size to maybe 1000K max. Come to think of it I don't remember any photos on this post. Here is one of my 25's, 1974. Notice the external coils.

It did feel hot to the touch. I had only been idling about 2 minutes when this happened so I was surprised it could overheat that badly in such a short time. Maybe it is something with the lower unit. I'll take it off and see if that frees up the motor.

I tried to figure it how to post photos early on when I started this thread. I'll take a pic to show the water level when I get back out there and try to resize and post it.

I use lit photo. Seems to work nice.

Well I pulled the lower unit off and it is still seized. Removing the spark plugs doesn't change that. What is the next step in trying to figure out what the extent of the damage is?
Pull the cylinder head?
I think I've attached a photo of my test tank. Hard to see in the pic but the water is right away the level of the head of the rear mounting bolt for the lower unit. The larger bolt that faces down.

Nice photo. Water level is okay but when the exhaust is bubbling out, you may have too much air in the water and disrupt the flow to the water pump. That has probably got something to do with your water struggles. I have another observation. Was the head and exhaust cover always that color? If so then it had already been badly overheated.
Yes, your next job is to remove the cylinder head. Doesn't look real promising. You said early on that you checked compression and I remember it was around 100 PSI, right? If it is seized up from overheating, then we need to find you a good used powerhead. Tim's Outboard in Hackensack MN. 218 682 2331. (Mike or Dan).....Google them up, 5 star. Tell them who sent you, they will cut you a great deal.

Timguy- I'll confirm tomorrow but I don't think I've had any color change since this incident. In other words, yes it's always been this color. Compression was 99 and 102 when I checked at the start of this project. Is that on the low end? Meaning this motor had already been overheated and therefore was in bad shape?

As far as water level... where should it be? I had it lower, about 3 inches above the cavitation plate, when I started. Didn't realize it could also be too high.

I'll remove the cylinder head tomorrow. If it is truly seized from the heat then there will be obvious scoring of the cylinder walls correct? If that's the case I'll be calling Tim's Outboard. A
And once again, thanks for all your help.

Your okay with the water level, the higher the better. Compression is good enough but on the low side. As far as the overheating, it will cause the piston, usually just one of them, but sometimes both, to start melting along the cylinder wall and tightening up.....almost always on the exhaust side.

Pulled the cylinder head and im not sure how to interpret what I found. The cylinders are able to move freely through a part of the bore. Seems to hard stop right about when the top piston is even with the ports in the cylinder walls. The top of the cylinders and the part of the bore I can see appear to be smooth, bright and unscored. The pic above is the top cylinder. Will post a pic of the bottom as well. Not sure how good they are or if they're of any diagnostic value.

If I remove the exhaust cover will I be able to see the exhaust side of the pistons? Maybe inspect them for damage?

Bottom cylinder

2 questions...

1) Is there anything that could cause this partially stuck cylinder other than heat seizure that might be repairable? Broken piston ring? Broken reed valve?

2) Should I remove the exhaust cover to try to inspect the cylinders? Seems like all the little boys that hold it on might be prone to snapping during removal and cause more problems.

It actually looks pretty good. I'm puzzled that it would lock up. Its gonna be bad to try to remove that cover, probably gonna break those bolts/cap screws. A piston ring wouldn't just break and jam in a port, very unlikely. Did something jam it up under the flywheel?

I hadn't thought about that Timguy. I'm working today but I'll take the flywheel off tomorrow and see if it's catching something under there.

Tim... No disrespect or intention of offense aimed your way Tim but I have to disagree on the water level thingy. The photo sort of gives an optical illusion of sorts but it looks to me that the water level is about midway of where the water pump is. I feel that the water level should always be 2" or 3" completely above the water pump area to eliminate the chance of the pump drawing air.

Mike... If the pistons move at all, I'd diagnose that the engine hasn't seized do to overheating but rather then something coming loose as Tim suggests. I'm in agreement with Tim that the magneto is the first place to look, and if nothing is obvious there.... a tear down of the powerhead would be next in line.

I will plan on look iil lol ok

I will plan on look iil lol ok

Apologies for the last 2 posts. My phone posted those accidentally.

Joereeves- since I have been unable to figure out why it's not pumping water I'll definitely get the water level well above the pump to rule that out. I may lower my outboard stand so I can get the leg deeper in the water. I would hate to kill a motor over something as simple as that. I have no experience with outboards prior to this project and I'm trying not to make any dumb mistakes.

I hope that it is something as simple as a loose part under the flywheel. I'll tear into it tomorrow and report back what I find. Thanks again to everyone for all the advice.

Your right, Joe. Now that I zoom into the water level, it should be higher. I also see a mark in cylinder near the edge of an exhaust port, but really nothing alarming. We really can diagnose better when our boaters post accurate photos. We should always encourage them to do that when we know it can help. Sure makes the job more interesting for me because my brain can connect directly to the project. Also we know its not some fabricated thread to try and mess with us.

Now that Timguy told me the best way to post photos I'll be putting in plenty. A picture really is worth a thousand words. I appreciate all the help so I'm happy to do anything I can to help the experts see what's going on.

Easy on the "expert" with me. I'm still learning, but pretty decent on the pre 2000 vintage stuff. I really don't embrace today's technology that much.....you probably can tell. Love my 74 Chev pickup. Wouldn't buy a new one if even I had the money.

Timguy and Joereeves- Looks like you were right again. Pulled the flywheel and found a crunched condenser and bent coil. With the flywheel removed the motor turns over easily. On further inspection the mounting bosses on the armature plate for that coil are also broken.

I know exactly what happened. The mounting hole for that condenser was a bit stripped out. Instead of taking the armature plate off and re-tapping the hole I wrapped the screw with Teflon tape a few times to get it to grab. Thought it was fairly snug and I clearly underestimated the force of vibration on that screw. I think it vibrated loose and the condenser got caught by the flywheel. Which pushed it into the coil hard enough to break the mounting bosses. I removed the armature plate and it looks like the support plate under it, crank shaft and Woodruff key are undamaged.

I took a shortcut and looks like I paid the price for it. But in the grand scheme of things it's way better than the seized motor I thought I had. Timguy I'll be calling Tim's Outboard today to see if they have a used armature plate.

A guy I used to work for building houses always said "If someone tells you they're experienced at doing something it means they've screwed that up before". I'm quickly becoming experienced at working on this outboard.

Mike from Atlanta said:

A guy I used to work for building houses always said "If someone tells you they're experienced at doing something it means they've screwed that up before". I'm quickly becoming experienced at working on this outboard.

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Yeah... us old timers have been down that road. Patch work does have its consequences... having 20 horses smash into that coil, OUCH! Lucky though as I've seen the top flanges of powerheads torn off by just that.

Myself... my fridges ice-maker quit working. Probably used the wrong gear-lube! :rolleyes:

joereeves said:

Yeah... us old timers have been down that road. Patch work does have its consequences... having 20 horses smash into that coil, OUCH! Lucky though as I've seen the top flanges of powerheads torn off by just that.

Myself... my fridges ice-maker quit working. Probably used the wrong gear-lube! :rolleyes:

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What I keep in mind is your life could depend on your outboard,it's not a good policy to cut corners