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, have a 1979 evinrude 4 cyl. cylinder three and four…

Customer Question
***** ***** Mechanic's...

***** *****

Mechanic's Assistant: Thanks. Can you give me any more details about your issue?

Have a 1979 evinrude 4 cyl . cylinder three and four are not working. have great spark. but after running engine, both lower cylenders are dry and plugs look brand new

Mechanic's Assistant: OK got it. Last thing — JustAnswer charges a fee (generally around $26) to post your type of question to Boat Experts (you only pay if satisfied). There are a couple customers ahead of you. Are you willing to wait a bit?

How long

Submitted: 2 years ago.Category: Boat
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1/20/2016
Marine Mechanic: Tan, MerCruiser Certified Technician replied 2 years ago
Tan
Tan, MerCruiser Certified Technician
Category: Boat
Satisfied Customers: 11,282
Experience: 40 yrs. experience with complete engine repairs both inboard/outboard and MerCruiser Certified Technician.
Verified

Hello. My name is Tan.

This is usually caused by a clogged carburetor. The top 2 cylinders work from the top carb and the bottom 2 cylinders work off the bottom carb. Now since you have spark that leaves the bottom carb as the possible issue.

Now it can be more serious the bottom crankshaft seal fails then the bottom 2 cylinders won't work correctly. Now what we can do is remove the bottom drain plug on each side of the bottom carb. Do you have fuel?

Post back with findings and questions.

We should also do a compression test to eliminate a possible compression issue.

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Customer reply replied 2 years ago
fuel in carb. compression is 100 and 100
Marine Mechanic: Tan, MerCruiser Certified Technician replied 2 years ago

How long has the engine been sitting since it ran correctly?

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Customer reply replied 2 years ago
started running weird about three month, has not been sitting. trying to get it right and running each month
Customer reply replied 2 years ago
when I put it in the water and start it up. I get raw fuel coming from around the lower unit and exhaust covers.
Customer reply replied 2 years ago
have to log out. will check shortly. thanks you
Marine Mechanic: Tan, MerCruiser Certified Technician replied 2 years ago

Raw fuel is caused by a flooding carb, bad fuel pump or weak spark.

If you squeeze the primer bulb does it get firm or can you continue squeezing the bulb

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Customer reply replied 2 years ago
the problem is, I am not getting any fuel to the bottom cylinders , even with fuel in the lower carb. my plugs are dry.
Marine Mechanic: Tan, MerCruiser Certified Technician replied 2 years ago

Then you have a clogged up carb. I posted that in my first sentence. That is the purpose of squirting fuel into the bottom carb to be sure the cylinders will fire.

From here we have to verify. This is the purpose of the tests I posted. This is a process of elimination.

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Customer reply replied 2 years ago
blub ferm
Marine Mechanic: Tan, MerCruiser Certified Technician replied 2 years ago

That tells us you don't have a bad fuel pump or flooding carb. Next is squirting fuel into the carb. If it doesn't fire then we have to check the quality of the spark. The spark must jump a 7/16" gap on a spark gap tester to fire the fuel.

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Marine Mechanic: Tan, MerCruiser Certified Technician replied 2 years ago

Ok Bobby I'm logging off for the night. Let me know what you find after the tests I posted and we can continue tomorrow.

If the engine runs better when you squirt fuel into the bottom carb the bottom carb has clogged jets. Remove the carbs disassemble, clean and install carb kits.

Thank you.......Tan

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Category: Boat
Satisfied Customers: 11,282
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Experience: 40 yrs. experience with complete engine repairs both inboard/outboard and MerCruiser Certified Technician.

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