1975 70HP Johnson

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bkabela

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I have a 75 70HP Johnson that seems to be having fuel related problems. There are 3 carbs on the engine, the middle one being the main one that connects from the fuel pump and then has a separate outlet that splices to the other two. All the lines are getting fuel, but the carb bowls don?t seem to be filling up. I have tried to crank ad crank to get it to start up, but it won?t. When I put some starting fluid in to each carb and it will start up but then die. I hope I'm posting this in the right section, thanks for any help you can offer.
 
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papaterk

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Re: 1975 70HP Johnson

You will probably have to pull the carbs and clean. Float shoud set parralell with carb housing upside down, and drop setting should be about 1 1/2 inches. Check all fuel lines. I understand the ethanol blended stuff will damage the lines on older units.
 
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papaterk

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Re: 1975 70HP Johnson

BTW, don't overdo it on the starting fluid. Yeah it's great to hear it run, but that stuff is too dry and won't lube the cylinder. If it won't start on gas, there is something still wrong.
 
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bkabela

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Re: 1975 70HP Johnson

papaterk, thanks for the reply. My dad and I took off all three carbs and cleaned them up. When we put them back together and fuel started to fill up the bowls. The engine will start up and continue to run, but only if we spray a little bit of starting fluid in the carb, once it starts up it stays running, however if we shut it down and let it sit for say 10 mins it won't start up unless we spray starting fluid back in it, guessing it?s still not getting all the fuel it needs, but it will stay running once started, kind of odd. All the lines are clean and clear, I do plan to replace them though.
 
SparkieBoat

SparkieBoat

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Re: 1975 70HP Johnson

get a spray bottle for oil products, and use premix fuel instead of starter fluid. ..does your choke work?? this should get enough fuel in there to crank without starter fluid. all 3 butterflies must be completely closed when choke is on. I have heard of people upgrading to the solenoid injection system..but choke always worked great for me..I had a 79 85HP that cranked up perfectly with choke. check coils with sparks gap tester and install new champion plugs.
 
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bkabela

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Re: 1975 70HP Johnson

The choke seems to work fine, I have it set to Auto, but I can use the switch on the Remote to choke it. I will have to look at the plugs tomorrow. Thanks for your help.
 
SparkieBoat

SparkieBoat

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Re: 1975 70HP Johnson

make sure all 3 butterflies are closing completely, they can get out of adjustment...this should get enough fuel in pistons to start engine..if you still have issues and you are sure your carbs are ok, check spark and plugs and plug wires. I have also seen situations where the rectifier/regulator was bad and cause hard cranking issues. CDI Electronics have great troubleshooting PDF files in their support page and on the install sheets for each part.
 
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