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Tan, MerCruiser Certified Technician
Category: Boat
Satisfied Customers: 10587
Experience:  40 yrs. experience with complete engine repairs both inboard/outboard and MerCruiser Certified Technician.
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I have a 1984 75 hp evinrude, was running at top speed, did

Customer Question

i have a 1984 75 hp evinrude, was running at top speed, did not hit anything, engine started to slow still at full throtel. just replaced prop, fuel filter clean. motor reves in idle.
will not get to plain, motor strains in gear
Submitted: 6 months ago.
Category: Boat
Expert:  Tan replied 6 months ago.
Hello. My name is ***** ***** to do a spark and compression test too eliminate these as possible causes of engine loss of power.The spark must jump a 7/16" gap on a spark tester and the compression must be 90+ psi with no more than 15% difference between cylinders. Post back with findings and questions.
Customer: replied 6 months ago.
could this happen suddenly on the compression to make the boat lose power like it did?
Expert:  Tan replied 6 months ago.
Absolutely same with spark.When you have the engine running try choking it when getting on plane. Does it run better?Try squeezing the primer bulb when getting on plane. Does it run better. If no change with these 2 tests that leaves compression or spark.
Customer: replied 6 months ago.
I will give that a try and let you know what happens. Thanks for your help.
Expert:  Tan replied 6 months ago.
Your welcome.If the engine runs better choking then you have a clogged carburetor. If it runs better squeezing the primer bulb you have a fuel delivery issue failing fuel pump or fuel restriction.To determine which run the engine on a different fuel source. If runs the same then you have a failing fuel pump. If it runs better on the other fuel source you have a fuel restriction in the boat side fuel system.If the compression is bad on one cylinder this will require further diagnosis. If you have a misfire or no spark we can do some tests with and ohm meter to determine the cause. Thank you........Tan Post back with questions and findings.Follow up questions are always welcome at no extra charge even after you have positively rated my service. Please don't forget to positively rate me as that is the only way I get paid for my service.Thank you.....Tan

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