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  #1   IP: 137.200.32.6
Old 07-10-2018, 02:01 PM
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2 dead engines in 1 week

My son commutes to work by boat. Coming into work, his Yamaha 15 HP outboard quit. We could get it to run at full throttle, but it dies at part throttle. Took that engine home and put the 6 HP Johnson on. A few days later that one died too
The 6 HP has 30 PSI compression on one cylinder and 50 on the other. That may have something to do with it, it probably blew the head gasket between the two cylinders.
The Yamaha was not improved by two carb cleanings and a new fuel filter. I gave up on that one, it is at the dealer now. Obviously there is some part of the carb I am not getting to or a real oddball issue and I am out of time to mess with it. Taking the head off the Johnson soon to see about the gasket. That may not be too hard of a fix.
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  #2   IP: 172.95.97.58
Old 07-10-2018, 02:13 PM
Dave Neptune Dave Neptune is offline
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Joe, the lack of compression on many 2 strokes can be from something stuck in a reed or the reed is not fully closing. Can make them a bit hard to start and rough running at idle and low speeds however you may not notice at all above 2500 or so.

On the Yamaha carb were you able to get an air gun to the intermediate and idle circuits?

Dave Neptune
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  #3   IP: 32.211.28.40
Old 07-10-2018, 02:22 PM
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My last two-stroke outboard engine problem was due to a piece of plastic lodged in the reed valve.
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  #4   IP: 137.200.32.6
Old 07-10-2018, 02:25 PM
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I did blow it out. Not sure what would get in there, the engine has a fuel filter that in theory would be grabbing any crud. The dealer says they pretty much could stay in business doing nothing but carb cleaning, so obviously something does get in there somehow.
Frustrating numbers:
New carb $250
Dealer repair $187
Chinese knock off fleabay carb $49. No idea how many days that would last
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  #5   IP: 137.200.32.6
Old 07-10-2018, 02:26 PM
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Quote:
Originally Posted by Al Schober View Post
My last two-stroke outboard engine problem was due to a piece of plastic lodged in the reed valve.
I'll take a look at that. Also I think there is a crankshaft seal at the top that is needed for compression. If I get ONE of these working, I can take my time with the other one. Unfortunately this isn't for fun, it is daily transportation to work.
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  #6   IP: 24.224.194.51
Old 07-12-2018, 05:42 AM
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Hi Joe. My outboard 4 hp single cyl Suzuki wouldn't start. I'd left it on the dinghy at the dock the year before last and hadn't used it for over a month. When I went to use it the engine wouldn't start. Tried cleaning carb etc and then checked compression...it was 60 psi. Ended up taking it home and never got at it until this spring. It's a 2 stroke.

This spring: Ordered a reed valve for it and broke the engine down. Found that the reed valve was fine, however the rings were stuck and I had a heck of a time freeing them. Finally, after an hour or so messing with it carefully...and with no luck, I poured some acetone on the piston right out of the can. After a few minutes they loosened up and I was able to remove the rings and clean them. It was like they were super glued in there, no rust, no evidence of water incursion etc...just like the lubrication turned to glue. The rings, piston and piston bore were all in great shape. Put it all back together and it worked.

I'd never seen that happen to an engine that was laying up before. I know the sun was beating on it all day long during that summer but boy, that was some serious "glueing" effect going on there. Last weekend I used the zodiac and engine (worked perfect) and as soon as I got home I took it all home again and put it in the garage...out of the sun.

I am wondering if something has changed in the oil composition with these 2 strokes or if this is a known thing. I use only high test gas as well, no ethanol.
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Last edited by Mo; 07-12-2018 at 05:48 AM.
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  #7   IP: 137.200.32.6
Old 07-12-2018, 06:44 AM
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This engine died as it came off full power to pull into the dock. The mechanic that has my Yamaha told me he thinks the head gasket blew between the two cylinders. If so - that is about $20

I am not sure about the oil, but I always run the gas out when done for the day and use fogging oil when the engine sits over the winter. I left a motorcycle at flight school for 3 months once and when I got back the engine was frozen solid
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  #8   IP: 137.200.0.109
Old 07-13-2018, 11:26 AM
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The 6 HP Johnson cylinder head gasket had essentially vanished between the two cylinders
One head bolt snapped off too There is some nasty corrosion in the cooling passages. I would guess at 18 years old, this engine is about 50% of the way to corroding right through in a few spots.
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Old 07-13-2018, 12:24 PM
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Joe, you could try some acetone to break up the corrosion around the stud left in the block. I draw some up in a syringe and put a bit right where it's needed. For stuff like that I don't mix it with transmission fluid...just need it to work it's way down and do it's thing. Worth a try if you have something to grab onto and back it out.
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  #10   IP: 172.95.97.58
Old 07-13-2018, 01:55 PM
Dave Neptune Dave Neptune is offline
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Joe, vinegar works pretty well in OB bolts too. Propane torch as a last resort.
Put the head on with Av grade and coat the studs/bolts~this stuff seals great. Will take a few more torque sequences though.

Good luck.

Dave Neptune
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  #11   IP: 137.200.0.109
Old 07-13-2018, 02:59 PM
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I still have about 3/4" of the bolt showing now the head is off. The center two bolts needed full force on a breaker bar and some of the others were almost finger loose.
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  #12   IP: 172.95.97.58
Old 07-13-2018, 03:22 PM
Dave Neptune Dave Neptune is offline
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Joe, smack the offending bolt "IN" a few times. The reversal of the "strain" often breaks them loose.

Dave Neptune
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  #13   IP: 137.200.32.54
Old 07-20-2018, 10:43 AM
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The Yamaha lives The shop found a carb blockage that was someplace I hadn't got to. This does raise a question: The engine itself has a "mini-Racor" fuel filter that is about the size of 2 35mm film canisters. Granted it isn't going to hold much if any water, but whatever clogged the carb made it through that filter screen or was created in the carb itself
This seems to happen to A4s now and again as well. The mechanic suggested adding an actual Racor type filter - done! - and ALWAYS running the gas out. My son has been advised
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  #14   IP: 137.200.32.54
Old 07-20-2018, 10:45 AM
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Quote:
Originally Posted by Dave Neptune View Post
Joe, smack the offending bolt "IN" a few times. The reversal of the "strain" often breaks them loose.

Dave Neptune
Doing that today - thanks!
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