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Tan, MerCruiser Certified Technician
Category: Boat
Satisfied Customers: 10979
Experience:  40 yrs. experience with complete engine repairs both inboard/outboard and MerCruiser Certified Technician.
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1993 70 outboard baugs out when in forward gear but not in

Customer Question

1993 Johnson 70 outboard baugs out when in forward gear but not in reverse. Had same problem a year back which prompted us to replace the fuel pump. this solved the problem until now. Any idea of possible or most probable cause? Any idea of what I should expect to pay for carb adjustment. Is carb adjustment something that I could perform (I am somewhat mechanically proficient - to a point) with some direction?
Thanks, *****
Submitted: 1 year ago.
Category: Boat
Expert:  Tan replied 1 year ago.

Hello Dave. My name is Tan.

This will take more than one reply to find the cause of your issue.

We need to do a couple of checks to find the cause of your problem. The symptoms are of fuel starvation from the carburetors. But lets be sure.

We need to check spark and compression on all cylinders to be sure they are good. The spark must jump a 7/16" gap on a spark gap tester. Then the compression must be 90+ psi on all cylinders.

Then when you are running the boat choke the engine when it starts to bog? Does it run better?

If no change squeeze the primer bulb when the engine bogs. Does it run better?

These carburetors have fixed jets so there is no adjustments you can make to make the engine run any better.

You have one of 3 problems 1) loss of spark 2) loss of compression. 3) Fuel starvation problem.

Do these checks and post back with findings and questions.

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