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Posts: 260
Location: Almost Heaven | Low compression on #1 cylinder on 150 horse Johnson. What have you guys found to be some of the causes and fixes in general? Thanks much.
Edited by Turkeyt 3/26/2013 6:42 PM
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Posts: 256
Location: plant earth | It could be a few things. Bad rings, cracked, warped,or excessive wear on cylinder wall. Possible bad valve or the valve seat. Head gasket is another. Check the oil and see if the is water in it. You may find some type of oil additive to make a temp fix but I wouldn't trust it. Good luck. |
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| jdeezay74 - 3/20/2013 4:30 PM
It could be a few things. Bad rings, cracked, warped,or excessive wear on cylinder wall. Possible bad valve or the valve seat. Head gasket is another. Check the oil and see if the is water in it. You may find some type of oil additive to make a temp fix but I wouldn't trust it. Good luck.
check oil? valves? how do you even know its a 4-stroke? I think he is gonna have to be a little more precise with his make model and year?
Edited by leech lake strain 3/20/2013 6:47 PM
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Posts: 260
Location: Almost Heaven | leech lake strain - 3/20/2013 7:45 PM
jdeezay74 - 3/20/2013 4:30 PM
It could be a few things. Bad rings, cracked, warped,or excessive wear on cylinder wall. Possible bad valve or the valve seat. Head gasket is another. Check the oil and see if the is water in it. You may find some type of oil additive to make a temp fix but I wouldn't trust it. Good luck.
check oil? valves? how do you even know its a 4-stroke? I think he is gonna have to be a little more precise with his make model and year?
It's an older 2 stroke 150GT Johnson |
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Posts: 3486
Location: Elk River, Minnesota | Hiya,
If you take the motor to a service shop, have them perform a leak-down test on the cylinders. This will determine if the problem goes beyond being bad rings on the piston, as they can determine if the cylinder itself is shot, a head gasket is bad or the head is warped. In all three of these situations, the leak down test can determine if the leak is external or internal, whereas a compression test usually determines only if rings are bad.
A quick test with compression is to squirt some oil in the cylinder and then re-do the compression test. If the compression stays high with very slow leaking, it is probably in need of new rings. But...this only works if the head is not leaking.
The leak down test will determine where the leak is happening as the cylinder is maintained under pressure, and external leaks are found by spraying soapy water or windex around the head (bolts, gasket, etc.) If the leak is external, it will show in the form of bubbles. If it is internal, you can literally hear the air moving by. If the latter of the two happens, it's rebuild time. With the Age of the motor, though, the cost of a rebuild may not be worth it as it could cost more than the motor is worth... It may be less than a replacement, though, and a good rebuild will have that motor running for years to come.
Steve
Edited by VMS 3/20/2013 8:07 PM
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| It would be a quick thing to do a de-carb and then check it again. Could just be carbon deposits. Maybe not but worth trying and cheap. |
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Posts: 1091
Location: Hayward, WI | Decarbon and retest. If still low pull the head and look for scoring on the cylinders wall. You might be able to take a small flash light and look through the spark plug hole and see some of the cylinder. If there is scoring it will need to be rebuilt. |
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Posts: 260
Location: Almost Heaven | I decided to check the low cylinder on 2 stroke 150 Johnson today. I could not even get any compression. Not good, when i pulled the head the cylinder was coated with metal and the edge of the piston on the left side was missing. Man, that thing got scorched. The motor had a new VRO pump but who knows what happened. The plug had crusty deposits and all the other plugs looked good as well as the other cylinders on that side. What could have cause this and can these motors be reworked? It is a project but i would like to get it going someday. Thanks and tite lines
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 150GT Johnson 006.JPG (92KB - 139 downloads)
150GT Johnson 001.JPG (99KB - 146 downloads)
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Posts: 532
| Is the #1 cylinder the top cylinder?
I had an old merc 90 tower of power that heat seized the top piston because of an air pocket in the cooling chamber. Wondering if that maybe what happened to you. |
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Posts: 260
Location: Almost Heaven | anzomcik - 3/26/2013 8:33 PM
Is the #1 cylinder the top cylinder?
I had an old merc 90 tower of power that heat seized the top piston because of an air pocket in the cooling chamber. Wondering if that maybe what happened to you.
Yes, it is the top one. Motor is a V6 crossflow. |
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Posts: 540
| anzomcik - 3/26/2013 7:33 PM
Is the #1 cylinder the top cylinder?
I had an old merc 90 tower of power that heat seized the top piston because of an air pocket in the cooling chamber. Wondering if that maybe what happened to you.
Looks like scoring to the cylinder walls so no issue from above like spark plug or pre detonation. Must be inadaquate lubrication to that one like a faulty oiler or it could have just wore a ring out and broke it off in there. If it is wore rings you might of heard some engine noise like piston rattling ect?
After looking at it some more looks like the exhaust side is wear most of the scoring occured wich tells me inadequate lubrication!
Edited by leech lake strain 3/26/2013 8:55 PM
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Posts: 1184
Location: Iowa Great Lakes | Nothing a couple grand wont fix....Had my 115 rebuilt last spring was over $2300 on a 4 cylinder... I could have got by cheaper by just doing the bad cylinder but my mechanic would not warrenty it then.... |
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Posts: 260
Location: Almost Heaven | I had a man tell me it may have got water in the cylinder from a bad gasket. Whatever the problem it did not let up until it was toast. This pic is from the other side of the cylinder. Not as bad but not pretty.
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150GT Johnson 002.JPG (70KB - 144 downloads)
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Posts: 5874
| All that pitting on the top of the piston is pre-ignition damage. That thing got HOT, and the piston got so hot that it ignited the fuel well before it was supposed to. Scorching is a symptom. I'm saying that cyl lost lubrication, and that's started the inevitable. |
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Posts: 373
Location: Maine Township, MN | Might want to run pre-mix from now on. |
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Posts: 51
| Bad gas caused the problem.
+2 disconnect the vro and premix. |
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