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late 80s 50 hp 2 stroke . Basically idled ok for a while, but throttle up and nothing boat doesn’t accelerate and goes about 4 to 6 mph. I had er running today and pulled the top plug cap off and the motor didn’t sound any different. Pulled the middle plug cap and the motor died. Fired it up again and pulled the bottom plug and it didn’t run any different. When I would reconnect the plug caps I could here a contact sound like a spark ?? Sounds like I’m running on one cylinder . Do I just need to buy some new coils and plug wires ?? Any info is greatly appreciated please and thank you.
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sounds like it is only running on #2, but that is impossible .
check compression, and spark on all 3 and then see what timing is doing with a light -
I pulled 1 and 3 and it ran till I killed it. ??. I’ll get my timing light out tomorrow thanks.Comment
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pulling plug wires off while running can cause the voltage to jump at a place it is not suppose to harming components like a the coils.
did you pull them both at the same time?
as I said check compression 1st to make sure the cylinders are sealingComment
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Good compression. No not at the same time. Trying to locate a timing light.Comment
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Do that, but from age I would be leaning towards a good carby clean may be due. If it runs on one cylinder indicates engine can’t be bad and that timing is OK. Two coil failures at once is unlikely.Originally posted by Misfit171 View PostComment
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how do you know compression is good?Originally posted by Misfit171 View Post
they make spark testers and peak voltage reading meters to make sure the inputs to the CDI and out puts are good.
measure things.
checking timing means idle timing and making sure it advances as it should as the throttle is opened up.
if everything you test is in spec, then it is time to dig into the fuelComment
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Rebuilt the the carbs/cleaned very well actually they weren’t even dirty at all. Drained and cleaned fuel tank/changed water seperator also. Changed out fuel lines and fuel filter. New fuel pump new impeller. New spark plugs even changed out my carbs gas lines. I have a good compression tester and all cylinders tested within one or two psi of each other . I’ll test again with exact numbers. I ordered new coils /spark plug wires today hopefully rule something out. I have tested the spark with a light tester and all lite up? I just don’t think they are getting full power. I’ll do a better test tomorrow. I’ll probably pull my carbs and check them again but I usually do a very thorough job on them. I’ll get back with y’all after all that. Thanks for the help.Comment
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Ok I pulled my plugs again my number 3 plug the bottom one had little water droplets on it. Checked compression again ( mind you I did a compression check a few months ago and all was good?). Anyway was not pleased to see number 3 was reading 10 psi. The other two read 95 and 92 . I checked my spark with a spark tester and all three still make spark in the plastic tube. The piston is not seized . I tried the oil trick but No difference in psi. My google search makes me think possibly a head gasket leak which I’d be more than fine with hopefully no heat warpage. Really hope it’s not a ring issue or valve. Any ideas ?? Thank in advance.Comment
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ring and piston failure is possible, but that would not put water in the cylinder
time to tear it down and seeComment
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Hard to see that 10psi does not indicate a catastrophic failure on a two stroke engine. It would not be worn rings nor head gasket failure.
There would be substantial evidence around this gasket that will be seen.
If it were anything like little end or big end bearing failure or damaged conrod you would definitely hear it.
The only thing would be piston damage. There could be a hole in it from lean running. Or the ring (s) have snagged on a port and ripped a piece of the piston top off. Rings can break by an overheat and the loose ring fouling the port opening.
Water in the lower cylinder invariably occurs as a result of failure of the crankshaft seal. It could also get in there by corrosion or cracking failure of the exhaust cooling jacket.Last edited by zenoahphobic; 02-25-2020, 06:53 PM.Comment
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Took the head off and the Lower piston definitely looks a lot different then the other two. Cylinder doesn’t seem to be damaged. There was signs of water there though. The gaskets felt damp to the touch. The lower end of the head gasket definitely looked to be failing. I’ll try to take some pics for y’all . My biggest problem now is that half of my head bolts broke off. I heated them up, but they weren’t budging. Even the broken bolts were really tough to get out. When I did get them out there would be a greyish sludge on them . So basically I’m dead in the water until I can get them removed. Thanks for all the help. I’ll keep ya updated.Comment
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just how does a crankshaft seal failure put water in #3 cylinder?Originally posted by zenoahphobic View Post
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how did the piston look different?Originally posted by Misfit171 View Post
good luck getting the head bolts out
might need to take the block to a machine shop to have them removed.
but taking apart the motor even farther probably will cause more bolts to break off
if so it may be best to find another motorComment
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