Evinrude E-NATION, for those dedicated to water, power, fishing and fun
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Skipper
Posts: 5
Registered: ‎03-21-2020

Is Compression too low?

My 1994 60hp Johnson outboard starts up and idles just fine.  It runs great at full throttle, however, whenever I slow down it begins to spit and sputter and when I stop, it is hard to start just like its flooded.  I installed new plugs, cleaned carbs and new kits, replaced stator, timer base and power pac and plugs.  Compression reads 89,80 and 80. When I trailored the boat I noticed fuel coming from breather cover and running down outside of motor shaft.  Could compression be too low to burn fuel properly?

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Admiral
Posts: 8,844
Registered: ‎07-14-2011

Re: Is Compression too low?

A large amount of fuel coming out of the air silencer box usually means a fuel leak somewhere or a flooding carburetor.  Spitting while slowing down or at slow speeds means that one or more cylinders are running lean or there is a crankcase air leak.

 

Your compression numbers are low but the speed of the motor cranking over during testing, the accuracy of your gauge, and the amount of residual oil in the piston rings all can cause lower readings even if the motor is in good shape.

 

 

 


"There is never just one thing wrong with a boat";
                    -- Travis McGee, main character in a book series by John D. McDonald 


 



***************

The factory recommends that a properly trained technician service your Johnson or Evinrude outboard motor. Should you elect to perform repairs yourself, use caution, common sense, and observe safety procedures in the vicinity of flammable liquids, around moving parts, near high-temperature components, and working with electrical or ignition systems.

The information offered here is only general in nature and should not be construed as complete factory approved procedures, techniques, or specifications. Always use the proper service manual for your motor, up-to-date service literature, the correct tools, and have an understanding of how to proceed with troubleshooting and repair methods. If you are unsure or uncomfortable with a procedure, a situation, or a technique, enlist the services of a factory trained technician.


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Skipper
Posts: 5
Registered: ‎03-21-2020

Re: Is Compression too low?

Thanks for the advise Bluewater!  I ran seafoam through the motor and retested the compression.  Got 80 psi on all 3 cylinders. Another mechanic told me that since all readings were the same that I probably needed a new head gasket.

Do you agree?

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Skipper
Posts: 5
Registered: ‎03-21-2020

Re: Is Compression too low?

Thanks BluewaterBill for such a quick response and for your advise.
I ran seafoam through the motor and rechecked the compression. Got 80 psi on all 3 cylinders. Another mechanic told me that since all readings were the same that I probably needed to change the head gasket. Do you agree? This motor set idle for 9 years.
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Admiral
Posts: 8,844
Registered: ‎07-14-2011

Re: Is Compression too low?

Try again with a charger on the battery and a high-quality different gauge. If still low, pull the cylinder head and inspect

 

 

 


"There is never just one thing wrong with a boat";
                    -- Travis McGee, main character in a book series by John D. McDonald 


 



***************

The factory recommends that a properly trained technician service your Johnson or Evinrude outboard motor. Should you elect to perform repairs yourself, use caution, common sense, and observe safety procedures in the vicinity of flammable liquids, around moving parts, near high-temperature components, and working with electrical or ignition systems.

The information offered here is only general in nature and should not be construed as complete factory approved procedures, techniques, or specifications. Always use the proper service manual for your motor, up-to-date service literature, the correct tools, and have an understanding of how to proceed with troubleshooting and repair methods. If you are unsure or uncomfortable with a procedure, a situation, or a technique, enlist the services of a factory trained technician.


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Skipper
Posts: 5
Registered: ‎03-21-2020

Re: Is Compression too low?

Thanks again! Will Do!

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Skipper
Posts: 5
Registered: ‎03-21-2020

Re: Is Compression too low?

Thanks Again!  Will Do!

Highlighted
Mate
Posts: 1
Registered: ‎03-25-2020

Re: Is Compression too low?

[ Edited ]

If the compression ends up being too low in any of the cylinders, then your vehicle will not be able to drive normally. Then you will notice your engine performance is significantly reduced, making it difficult to accelerate and drive the car as usual dgcustomerfirst