1986 4 hp Evinrude poor idle

[Bayliner 18]

I need some advice. First off, this engine in an Evinrude Deluxe model # E4RDHCDE and it has great compression at 100 p.s.i. on both cylinders. Does anyone know why these engines might cough during idle? I've gone over every aspect, regarding mixture control and idle jets and float level/drop adjustments possible. (And yes, fuel pump rebuilt). These two cylinder engines should just purr. What I believe is going on is a poor set of reeds. I removed the carburetor and placed some thin plastic wrap over the intake then sandwiched it with the carb gasket and some short hose lengths over the bolts (1/4 inch) to hold the plastic in place. Pulling on the starter cord revealed that the plastic fluttered while being pulled. To me this indicates some blow back. Not enough to shoot fuel out of the carb intake but enough to cause issues, (probably)? This motor starts and runs but it also has a throttle spot, that just "takes-off" and doubles in rpm. Not smooth acceleration, that one would expect. Valves and timing are important on 4 strokes but proper valve seals would also be important on these engines as well. Am I right about this? The only other issue I have is with the pickup plate under the flywheel having some slack between it and the tiller handle and linkage train. This is probably normal?

 

[saltchuckmatt]

I need some advice. First off, this engine in an Evinrude Deluxe model # E4RDHCDE and it has great compression at 100 p.s.i. on both cylinders. Does anyone know why these engines might cough during idle? I've gone over every aspect, regarding mixture control and idle jets and float level/drop adjustments possible. (And yes, fuel pump rebuilt). These two cylinder engines should just purr. What I believe is going on is a poor set of reeds. I removed the carburetor and placed some thin plastic wrap over the intake then sandwiched it with the carb gasket and some short hose lengths over the bolts (1/4 inch) to hold the plastic in place. Pulling on the starter cord revealed that the plastic fluttered while being pulled. To me this indicates some blow back. Not enough to shoot fuel out of the carb intake but enough to cause issues, (probably)? This motor starts and runs but it also has a throttle spot, that just "takes-off" and doubles in rpm. Not smooth acceleration, that one would expect. Valves and timing are important on 4 strokes but proper valve seals would also be important on these engines as well. Am I right about this? The only other issue I have is with the pickup plate under the flywheel having some slack between it and the tiller handle and linkage train. This is probably normal?

100 psi is not what I would call great. Usually, coughing and sneezing is a result of carburetion. Sorry, I can answer the other questions.

 

[Bayliner 18]

100 psi is not what I would call great. Usually, coughing and sneezing is a result of carburetion. Sorry, I can answer the other questions.

Interesting comment. The piston diameter on these engines is less than that of a golf ball @ 1 9/16 inches. I've seen other forums where they could be in the 80's. I thought, a new engine might be as high as 110 p.s.i. for these twin cylinder 4 hp motors but I am not sure what they should be when new.

 

[Bayliner 18]

This post was originally from TinBoats.net The original aluminum boat site!
Outboard compression numbers
Quote

Post by cajuncook1 » 07 Jul 2011, 17:21

Well, comparing Mercury motor compression values to Evinrude/Johnson motor compression values is not comparable. That is like comparing apples to oranges, yes they are both fruit but they are different!!

I am a Johnnyrude guy, so I don’t have much experience with Mercury motors. It is my understanding that Mercury motors have always been high compression motors.

Also, you can not use the same values of compression when talking about higher hp motors compared to lower hp motors. Higher hp motors will have and require higher compression psi numbers compared to lower hp outboards. Also using compression numbers from new to late model outboards and comparing them to older outboards is not justifiable.

I am going to make some comments about compression related to Johnson and Evinrude motors, because am more familiar with motors from the 1950’s to mid 1980’s motors.

*** I own several Johnson/Evinrude outboard service manuals and none of them given compression reference ranges.** Over the years outboard mechanics would document in their notes service done on new or relatively low hour motors of compression and work they had done and how the motor ran. As time went on these same mechanics serviced these same make, model and era motors and would document the compression and work done on these now older and higher hour usage motors and how they ran. So, over a period of time the service industry developed an acceptable range of compression based on the make, model and year motors. Some motors were known to be lower compression motor off the bat.

Excellent example of what am referring to is the 9.5hp Evinrude/Johnson motor that where built from 1964 to 1973. It is not uncommon to find compression readings ranging from 55 psi to 80psi on these motors. Most of them are in the 60’s and 70psi range and they run fine. Some people have those same motors with the psi range in the 50’s but they do not have as much power and have dropped a few mph, but idle ok and are dependable.

You can not compare compression ratios from 25hp motor to that of 6hp motor.

25hp Evinrude = great compression would be > 125lb, (but run and idle ok at 100psi)

but

6hp Evinrude = great compression would be >85 to 90psi

Most of the Evinrude/Johnson motors 5.5hp to 6hp from 1950’s to late 1970’s had decent to good compression range from 60psi to 80psi. Then again, most of the motors from that era are found to be running fine with psi ranges from 60psi to 70psi.

So, they are not speed demons, they don’t have quite as much power and has lost a mph or two over 40 to 60yrs. That is pretty dang good if you ask me. If the motor is running fine, idles ok, gets you to the fishing hole and back and is dependable…..then that is what most of us are wanting!! Most of us can find those motors for less than $300 or $400 dollars. Beats paying couple of thousand dollars just for the motor. Any hoo off subject…sorry!


Again you can not compare different makes of outboards and different hp of outboard compression values and extrapolate if the compression is adequate or not.

Please be very careful when telling someone that has little or no knowledge about outboards that there compression values are too low and that should get rid of the motor or junk it. Unless you are very familiar with the year, make or model of the that outboard, you may be giving poor advice and that treasured outboard that belonged to their dad, grandfather or their only affordable means may be junked!!!

 

[racerone]

Compression on 2 strokes can be and is a mystery to some.----But 100 PSI on this motor is fine !----What other trouble shooting has been done. ?-----Does spark jump a gap of 3/8" on both leads ?----Is the high speed orifice clean ?----Is the fuel pump bladder ( orange bit ) in good shape ?----Sneezing is often caused by a lean fuel condition ?

 

[saltchuckmatt]

This post was originally from TinBoats.net The original aluminum boat site!
Outboard compression numbers
Quote

Post by cajuncook1 » 07 Jul 2011, 17:21

Well, comparing Mercury motor compression values to Evinrude/Johnson motor compression values is not comparable. That is like comparing apples to oranges, yes they are both fruit but they are different!!

I am a Johnnyrude guy, so I don’t have much experience with Mercury motors. It is my understanding that Mercury motors have always been high compression motors.

Also, you can not use the same values of compression when talking about higher hp motors compared to lower hp motors. Higher hp motors will have and require higher compression psi numbers compared to lower hp outboards. Also using compression numbers from new to late model outboards and comparing them to older outboards is not justifiable.

I am going to make some comments about compression related to Johnson and Evinrude motors, because am more familiar with motors from the 1950’s to mid 1980’s motors.

*** I own several Johnson/Evinrude outboard service manuals and none of them given compression reference ranges.** Over the years outboard mechanics would document in their notes service done on new or relatively low hour motors of compression and work they had done and how the motor ran. As time went on these same mechanics serviced these same make, model and era motors and would document the compression and work done on these now older and higher hour usage motors and how they ran. So, over a period of time the service industry developed an acceptable range of compression based on the make, model and year motors. Some motors were known to be lower compression motor off the bat.

Excellent example of what am referring to is the 9.5hp Evinrude/Johnson motor that where built from 1964 to 1973. It is not uncommon to find compression readings ranging from 55 psi to 80psi on these motors. Most of them are in the 60’s and 70psi range and they run fine. Some people have those same motors with the psi range in the 50’s but they do not have as much power and have dropped a few mph, but idle ok and are dependable.

You can not compare compression ratios from 25hp motor to that of 6hp motor.

25hp Evinrude = great compression would be > 125lb, (but run and idle ok at 100psi)

but

6hp Evinrude = great compression would be >85 to 90psi

Most of the Evinrude/Johnson motors 5.5hp to 6hp from 1950’s to late 1970’s had decent to good compression range from 60psi to 80psi. Then again, most of the motors from that era are found to be running fine with psi ranges from 60psi to 70psi.

So, they are not speed demons, they don’t have quite as much power and has lost a mph or two over 40 to 60yrs. That is pretty dang good if you ask me. If the motor is running fine, idles ok, gets you to the fishing hole and back and is dependable…..then that is what most of us are wanting!! Most of us can find those motors for less than $300 or $400 dollars. Beats paying couple of thousand dollars just for the motor. Any hoo off subject…sorry!


Again you can not compare different makes of outboards and different hp of outboard compression values and extrapolate if the compression is adequate or not.

Please be very careful when telling someone that has little or no knowledge about outboards that there compression values are too low and that should get rid of the motor or junk it. Unless you are very familiar with the year, make or model of the that outboard, you may be giving poor advice and that treasured outboard that belonged to their dad, grandfather or their only affordable means may be junked!!!

1st of all, I had a

This post was originally from TinBoats.net The original aluminum boat site!
Outboard compression numbers
Quote

Post by cajuncook1 » 07 Jul 2011, 17:21

Well, comparing Mercury motor compression values to Evinrude/Johnson motor compression values is not comparable. That is like comparing apples to oranges, yes they are both fruit but they are different!!

I am a Johnnyrude guy, so I don’t have much experience with Mercury motors. It is my understanding that Mercury motors have always been high compression motors.

Also, you can not use the same values of compression when talking about higher hp motors compared to lower hp motors. Higher hp motors will have and require higher compression psi numbers compared to lower hp outboards. Also using compression numbers from new to late model outboards and comparing them to older outboards is not justifiable.

I am going to make some comments about compression related to Johnson and Evinrude motors, because am more familiar with motors from the 1950’s to mid 1980’s motors.

*** I own several Johnson/Evinrude outboard service manuals and none of them given compression reference ranges.** Over the years outboard mechanics would document in their notes service done on new or relatively low hour motors of compression and work they had done and how the motor ran. As time went on these same mechanics serviced these same make, model and era motors and would document the compression and work done on these now older and higher hour usage motors and how they ran. So, over a period of time the service industry developed an acceptable range of compression based on the make, model and year motors. Some motors were known to be lower compression motor off the bat.

Excellent example of what am referring to is the 9.5hp Evinrude/Johnson motor that where built from 1964 to 1973. It is not uncommon to find compression readings ranging from 55 psi to 80psi on these motors. Most of them are in the 60’s and 70psi range and they run fine. Some people have those same motors with the psi range in the 50’s but they do not have as much power and have dropped a few mph, but idle ok and are dependable.

You can not compare compression ratios from 25hp motor to that of 6hp motor.

25hp Evinrude = great compression would be > 125lb, (but run and idle ok at 100psi)

but

6hp Evinrude = great compression would be >85 to 90psi

Most of the Evinrude/Johnson motors 5.5hp to 6hp from 1950’s to late 1970’s had decent to good compression range from 60psi to 80psi. Then again, most of the motors from that era are found to be running fine with psi ranges from 60psi to 70psi.

So, they are not speed demons, they don’t have quite as much power and has lost a mph or two over 40 to 60yrs. That is pretty dang good if you ask me. If the motor is running fine, idles ok, gets you to the fishing hole and back and is dependable…..then that is what most of us are wanting!! Most of us can find those motors for less than $300 or $400 dollars. Beats paying couple of thousand dollars just for the motor. Any hoo off subject…sorry!


Again you can not compare different makes of outboards and different hp of outboard compression values and extrapolate if the compression is adequate or not.

Please be very careful when telling someone that has little or no knowledge about outboards that there compression values are too low and that should get rid of the motor or junk it. Unless you are very familiar with the year, make or model of the that outboard, you may be giving poor advice and that treasured outboard that belonged to their dad, grandfather or their only affordable means may be junked!!!

First of all I had a 4hp Deluxe and it had much higher compression than yours. It was used so I can't speak about what it had when new. I have also ran compression checks on many small motors that were much higher than you say. Not sure piston size means anything. Most outboard mechanics will tell you that on a two stroke compression doesn't always tell the story why a motor isn't running correctly. They do always say the they should be close to the same though. I ve seen them run as low as 90 lbs though and usually they started even easier because they were so loose. My comment wasn't to say to throw it away, my comment was that 100 is not great....it certainly acceptable and not why your engine is having problems.

 

[Bayliner 18]

Compression on 2 strokes can be and is a mystery to some.----But 100 PSI on this motor is fine !----What other trouble shooting has been done. ?-----Does spark jump a gap of 3/8" on both leads ?----Is the high speed orifice clean ?----Is the fuel pump bladder ( orange bit ) in good shape ?----Sneezing is often caused by a lean fuel condition ?

Yes, I agree "Sneezing is often caused by a lean fuel condition." Spark is great and consistent, fuel pump rebuilt and high speed jets and low speed orifices cleaned out. This engine has a mixture control originally set at 1.5 turns and then adjusted in both directions. The seals are firm and not an issue. However, I believe poor reed performance might the culprit. They should contact (come to rest) on the backing block and not leak any (receding) piston cylinder back pressure. My theory is the engine is not breathing properly or as good as it should. The cylinder draw fluctuates and this might be overlooked, by many?

 

[racerone]

Put new reeds / reed plate in and test run.-----I truly believe it will get rid of the sneezing / cough.