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Ask Dominick Your Own Question
Dominick, Marine Mechanic
Category: Boat
Satisfied Customers: 1009
Experience:  25 Years Experience as Mechanic, 20 Yrs Boat Yard Owner/Mechanic, Factory Certified
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I have a 1987 70 Johnson that runs great when in gear, but

Customer Question

I have a 1987 70 Johnson that runs great when in gear, but cant idle.
Submitted: 11 months ago.
Category: Boat
Expert:  Tan replied 11 months ago.

Hello. My name is Tan.

Has the boat been sitting? If you push in on the key real quick will it idle? Does the use of the primer/choke help at all?

Customer: replied 11 months ago.
Hi Tan,The boat had an engine rebuild done and then sat for a couple of years. Following that I had the boat taken to a mechanic and had all the carbs overhauled. Following the overhaul the boat ran great when in gear, but couldn't hold the idle. I took it back to the mechanic and he replaced the jets on the carbs and turned the idle up slightly. I have not attempted to use the primer/choke.
Customer: replied 11 months ago.
Also, boat idles perfectly on the muffs, just not in water.
Expert:  Tan replied 11 months ago.

Ok usually poor idle is fuel related. Do you know what he has the idle timing set at. Usually this can be bumped up a little. There is no idle adjustment on the carbs so something is set up wrong. If he is adjusting the linkage to get the idle speed up the syncronization and linkage is out of adjustment. These engine should run with the carburetor plates completely closed.

Try the primer/choke. If it runs better then the idle tubes in the carbs are clogged still. If no change the idle timing and syncronization to be be adjusted.

Customer: replied 11 months ago.
Ok I will get the boat on a lake and give it a try. Since you say it may be fuel related would it be a good idea to run a can of seafoam through the motor?
Expert:  Tan replied 11 months ago.

Can't hurt. Usually if the idle tubes in the carbs are plugged real bad the carbs have to be cleaned in a ultrasonic carb cleaner.

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