Johnson outboard blowing steam!?!

[dhaglund]

Here is a tricky one for you all...

I bought this Johnson 30 hp -05 2-stroke recently. First trial run we were three in the boat and couldn't get on plane unless we kept pumping the fuel primer. The motor started easily enough and ran fine at idle and up to about half throttle, after that it would bog down completely unless someone was pumping the primer at a slow steady pace. I figured it was most likely a carburetor issue. The previous owner hadn't run the engine this year but it ran fine last year. Nothing had been done to the motor since.

So my son tore down the carb only to find that it was spotless! The PO cleaned it last 4 years ago. I changed the whole water pump since the PO couldn't say when the impeller was changed last and I had noticed white smoke coming from the exhaust when we ran it. I figured this was steam and perhaps a new impeller would make a difference, although it seemed ok already from looking at the telltale.

The new water pump made the stream from the telltale even stronger. Second trial run it ran just the same. Fine until half throttle. But after a few minutes it started to blow steam badly and finally died. I could not start it back up, there was no ignition at all. But pulling the cord felt as usual. I didn't have time to mess with it more that day.
https://photos.app.goo.gl/fhdd6FSeZkLAUq8S9

The next day I had switched to another gas tank/fuel hose and fresh fuel. The motor started easily and ran with earmuffs on high idle producing a nice stream from the telltale. So we took it to the lake and it ran like before. Fine up to half throttle but after a while it started blowing steam and died. This time I was able to start it back up after letting it cool some.
https://photos.app.goo.gl/XK7MRU3nYwcsGj767

So, what is the verdict on this one? Since pumping the primer at full throttle makes a positive difference this indicates a fuel delivery problem. For some strange reason the engine is getting hot and I'm guessing that the temperature sensor is killing the ignition until it cools down. Can anyone confirm that this engine has that feature?

Spark plugs look good to me. A nice tan colour and not wet. I tested the compression before I bought it and it was great. I took the thermostat out and it tested ok. Opened and closed in water like it should.

I will check the fuel pump next. Can a bad head gasket cause issues like this? Or can lean running cause the engine to overheat like this? I've only run the 10 minutes or so at a time, mostly at part throttle.

[dhaglund]

Tip. If you download the videos (hit Shift-D when playing) and watch offline you will probably get better video quality.

[neil.mccrirrick]

I’d be looking at the fuel pump and the water pump, specifically the housing to see if it’s losing pressure.

[dhaglund]

Originally Posted by neil.mccrirrick

I’d be looking at the fuel pump and the water pump, specifically the housing to see if it’s losing pressure.

It would be strange if two different water pump are defective. Since both the old and new produce similar results.

[dhaglund]

I just took the fuel pump apart. Apart from the odd two strands of hair I found in a corner inside it is really clean. Gaskets look like new and I can't find any holes in the membrane. It looks very good as well.

[dhaglund]

Fixed links:
Second run

Third run

[Peter_C]

The engine will run off of full carb bowls for a over a minute. Most likely not a problem with fuel getting to the carbs, with the issue being from the carb into the engine. A simple vacuum leak would most likely show up by not idling well at all.

Pumping the fuel bulb with it running might help induce just enough to help it get a little power. Running lean will cause more heat but it will be inside the cylinder.

If you ever see steam from the tell tale shut it down as it is overheating and not getting water over the cylinder head, damage is occurring.

The thermostat could have failed. Removing it and testing it in a pot of water while measuring temperature can confirm. I would be severely worried about steam and not having proper water flow.

If a water way is close I would take the boat out with the engine cover off, and spray some carb cleaner/brake cleaner/or better still starting fluid into the plenum while trying to go past 1/2 throttle. If it runs better it is totally a fuel issue and cleaning the carbs more thoroughly is in order. Cleaning carbs requires complete disassembly including ALL the jets and orifices, then using high pressure air and cleaner to blow thru everything, multiple times and multiple directions. You may never see the difference visually but all of a sudden the motor will run like a champ again.

I used to have a 40hp Evinrude and when the black box for ignition failed it ran great at idle to about 40% throttle, then proceeded to fall flat on it's face. After verifying it wasn't a fuel issue I took a wild guess and replaced the ignition box and it was back to running great. No real diagnostic without a lab scope for which I tried a Snap-on MODIS 4 channel scope but failed to capture the failure for absolute diagnostics. *shrugs* sometimes you just gotta throw parts at things.

I would guess you have two separate issues.

[AdamB1]

It sounds like an overheating issue to me. If it were an eTec, I would suggest the vapour separator tank, but you don’t have one.

The telltale looks strong but that doesn’t mean water is flowing through the whole power head. If you find a diagram of the water route, you will probably find there are some shortcuts the water can take.

By taking the cylinder head off, you could see if the water jacket is blocked. If you don’t have the experience, tools or € for that, you could try an acid water flush. One hour at tickover in a deep bucket of diluted brick acid solution, followed by a proper flush. It is not for the faint-hearted and risks aluminium damage, but it might clear a blockage in the water jacket. I did this on my eTec in the summer and it seemed to work a charm.

[Peter_C]

I would think it would be a lot easier to remove the lower drive unit and using high pressure air blow into the water pump ports to check if things are clear. Taking the head off is hours of work to R&R. Would also be a good time to verify impeller is still looking good, which should be the first inspection for the water cooling issue.

[Tommy c]

Originally Posted by Peter_C

I would think it would be a lot easier to remove the lower drive unit and using high pressure air blow into the water pump ports to check if things are clear. Taking the head off is hours of work to R&R. Would also be a good time to verify impeller is still looking good, which should be the first inspection for the water cooling issue.

I suppose it all depends what the obstruction is if there is a blockage.
Salt build up/corrosion won't shift using that method

[Nos4r2]

Thermostat (IF those had one) or more likely the gasket between the leg and the powerhead is leaking gas into the cooling water.

It's not an expensive fix, unless there's corrosion in there. Pop the powerhead off and have a look.

[dhaglund]

Thanks for the input!

I tried spraying starter gas into the carb while running in the lake. It ran well immediately. So there is a fuel delivery problem for sure. I seems to be leaking a little fuel somewhere so I'll get that sorted first. I also added a transparent fuel filter to the fuel hose just before the motor inlet. The fuel filter does not stay full.

Next I will check the impeller again just to make sure I didn't mess that up. While the lower unit is off I will also try to blow compressed air backwards into the cooling system and then flush with water the normal direction.

[Peter_C]

Most likely the carbs are still plugged with debris. Tear down again and use high pressure air to clear out each passage after removing all jets, emulsion tubes, etc. If you have access to a ultrasonic cleaner do that first with cleaner. You could soak just the jets and emulsion tubes in acetone or lacquer thinner for a little while to help clear them too. Something like torch cleaners for welding can also help to clear jets.

Fuel leaks are REALLY BAD on a boat. Please do fix it properly. The fuel filter being partially full is normal. If you can pump the fuel bulb hard, then the carbs are most likely full and all is well...unless fuel is now dripping somewhere. Hopefully you got a plastic fuel filter not one of the glass ones with pot metal ends? Those fail and gush fuel. Plus they do not filter nearly as well as a paper element.

Carefully inspect the water impeller gaskets and the impeller itself. My bet would be on a simple failure in that area.

[dhaglund]

So, I tore down the carb again, like my son had already done before. When putting it back together and watching this video from Dangar marine really carefully I suddenly saw him pull off a small gasket in the middle of the bowl that was not present on my carb!
https://youtu.be/x4AeAX6l8-M?t=715

Well, I've ordered a carburetor kit now. Meanwhile a made my own gasket and it made a big difference for the fuel delivery. I think it is fine now. I was only able to try this for a few seconds since the more serious issue, cooling, is not sorted yet. Also, fuel leaks seem to be fixed now after going over all fuel fittings and reconnecting the primer circuit.

I pulled the lower unit and some oily black water came out. This surprised me a bit but may be normal. The water pipe from the midsection came out with the lower unit and it was seated a bit too far down into the grommet so I reseated that at the top and hoped it would make a difference but no such luck. Cooling is still erratic. I can idle/high idle for 15 minutes with earmuffs without any problems. Temp is max 60C on the warmest spot on the block. But in the lake under some load the temp rises and the cooling starts acting up. Block temp went up to 73C before I shut it off. I will disassemble the water pump next.

[dhaglund]

Originally Posted by Peter_C

Hopefully you got a plastic fuel filter not one of the glass ones with pot metal ends? Those fail and gush fuel. Plus they do not filter nearly as well as a paper element.

Yes, I got a Mahle plastic filter so all should be good, but thanks for the tip.
Mahle filter

[Peter_C]

Originally Posted by dhaglund

I pulled the lower unit and some oily black water came out. This surprised me a bit but may be normal.

2 strokes often have black oil leaking from the prop area. Only a concern to the environment.

Originally Posted by dhaglund

The water pipe from the midsection came out with the lower unit and it was seated a bit too far down into the grommet so I reseated that at the top and hoped it would make a difference but no such luck.

Is it possible the tube isn't sealing? When running off the muffs does water leak out of weird areas? The muffs provide positive pressure which would lead me to surmise the water impeller is not sending pressure to the power head properly.

[dhaglund]

Originally Posted by Peter_C

Is it possible the tube isn't sealing? When running off the muffs does water leak out of weird areas? The muffs provide positive pressure which would lead me to surmise the water impeller is not sending pressure to the power head properly.

I tried to look for that without seeing anything out of the ordinary. I also lowered the pressure in the hose as much as I dared without seeing a weaker telltale.

[dhaglund]

I took the new impeller out, the one that has only 30 minutes of runtime or so. It is TOAST! Even the housing is toast! Note the large plastic shaving in the outlet hole. I don't know what happened here but the O-ring under the metal housing is ground down flat and part of the plastic housing is shaved off! But the metal cup was very firmly seated in the correct position when I pulled it out. And the metal tabs are intact! It does not make sense.

My only conclusion is that I must have twisted the impeller the wrong way when installing it. I've never been too concerned about that since I thought it would correct itself, if necessary, at first start. Well, it doesn't!




Considering the terrible state of that impeller it is impressive how well it worked, providing a decent-looking telltale. Luckily no parts seem to have fallen off the impeller.

[dhaglund]

Today I installed a second new impeller. Here is the video of that.
https://photos.app.goo.gl/frzg9KZPR2L6YYDD8

I also installed the correct missing gasket in the carb as well as a new needle and seat. The motor runs fine now but the white smoke is worrysome. I measured the temp while running and it was around 75C at the hottest place on the block.

[beamishken]

Originally Posted by dhaglund

I took the new impeller out, the one that has only 30 minutes of runtime or so. It is TOAST! Even the housing is toast! Note the large plastic shaving in the outlet hole. I don't know what happened here but the O-ring under the metal housing is ground down flat and part of the plastic housing is shaved off! But the metal cup was very firmly seated in the correct position when I pulled it out. And the metal tabs are intact! It does not make sense.

My only conclusion is that I must have twisted the impeller the wrong way when installing it. I've never been too concerned about that since I thought it would correct itself, if necessary, at first start. Well, it doesn't!

Attachment 141806
Attachment 141805

Considering the terrible state of that impeller it is impressive how well it worked, providing a decent-looking telltale. Luckily no parts seem to have fallen off the impeller.

Something wrong with the install or its been run dry to do that damage to a new impeller, they do correct if installed the wrong way , you often find one vane flipped the wrong way because engines rock back as they stop & invert the odd vane. Only time they dont correct is if its an old knackered impeller thats sat for a long time & "set" or gone hard. Even if every vane was wrong way you wouldnt have that damage, you need to look for another cause

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