troubleshooting a 1968 Johnson 6 hp

turbulence

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Sep 17, 2020
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I'm having some issues starting a cd-25r Johnson I just bought. I started it and ran it for a short period but am having problems getting it started again. I'm getting spark and gas and it sputters some. Anyone know what the compression should be for that motor?
 

Rick.

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I just sold my 68 Evinrude 6 hp and the compression was72 top and bottom with the motor warmed up. It ran very well at those numbers.
 

racerone

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Dec 28, 2013
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Test spark.----A good ignition system can jump a gap of 5/16", yes it can.----If coils are original they will be cracked and you need a set.----Pull the flywheel with the 3 holes ( 1/4-20 thread ) and inspect the magneto.
 

racerone

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When I pick-up one of these motors usually the first thing I do is pop the flywheel ( less than 10 minutes ) and see if it has new coils or old cracked ones.------If they are cracked it may indicate a motor that has been stored for many years.
 

turbulence

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Update on my project.
I checked under the flywheel, everything in there looked good but the points were a little close so I reset them to .020. I'm getting a good spark. I replaced the fuel lines which appeared to be leaking a little. I cleaned the carburetor which didn't look bad and the ports are clear. Fuel was spitting back out where the hose connects from the tank when I disconnected it and pulled the starter rope so I looked into the fuel pump. It had a little gunk in it which could have been fouling the valves. I checked the compression and got 35 lbs on each cylinder (cold engine with pull rope). I'm concerned with that but I will try the de-carbonizing process to see if that helps. I want to get this thing where it will start easily then I'll look at the water pump and lower unit.
 

racerone

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The original head gaskets were poor design.-----Replacements are a better quality.-=---SIERRA offers the best price.----Next step is to remove cylinder head.----Blown between the 2 cylinders ?---These are a wonderful motor.----Your grandkids will be running it if you maintain it properly.
 

turbulence

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I figured the next step would be to pull the head and investigate there. I've been looking for parts online and have found gaskets but can't find a set of rings. I may not need rings but would like to know they're available just in case. Any suggestions?
 

turbulence

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If in Canada -----evinrudeparts.ca ----may be able to help you.
The original head gaskets were poor design.-----Replacements are a better quality.-=---SIERRA offers the best price.----Next step is to remove cylinder head.----Blown between the 2 cylinders ?---These are a wonderful motor.----Your grandkids will be running it if you maintain it properly.
I pulled the head and just ask you suspected, gasket was blown between cylinders. Cylinder walls are smooth with no obvious wear:). I removed the lower unit and inspected the water pump, the impeller had a little wear so I will replace it along with the head gasket. I'll update when I get it back together.
 

turbulence

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Sep 17, 2020
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Replaced the impeller, head gasket and the thermostat. Compression is now 70 psi on both cylinders. Starts easy and runs good in the test tank. Haven't been on the water with it yet but I don't expect I'll have any problems with it when I do. Thanks for the help on this.
 
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