Need some input on 50 HP Johnson problem.

[Itsallalie]

Need some help figuring this out please. 1987 50 hp Johnson. Idles/runs fine until you reach the point where the boat should be coming on plane. After that it struggles to increase rpms. Does this about 90% of the time. Some times it will lag as described and then come up in rpms and run as it should. Engine has good spark and new plugs. Compression in both cylinders is around 160. New power pack. VRO system removed and new fuel pump and filter installed. Carbs and choke solenoid just rebuilt. All new fuel lines. Have 2 tanks and problem persists with either tank used. Non ethanol always used. Boat ran fine after above work was done for about 10 hours and then this started. Thinking about pulling the carbs again and looking them over but would appreciate any input on what else it might be. Thanks

 

[racerone]

Run with timing light hooked up 1 cylinder at a time and observe spark.

 

[Itsallalie]

Pulled flywheel and the key is fine. Not sure what I'm looking for with a timing light per your post?

 

[jimmbo]

To see if the Ignition System is not malfunctioning when the problem occurs

 

[Itsallalie]

Got it. Make sure each cylinder is firing when trying to come up on plane.

 

[racerone]

Sounds like it might be running on 1 cylinder at times.----Does spark jump a gap of 3/8" or better on a test device.----Sparkplugs are NOT used during this maximum output test.

 

[Itsallalie]

I have a tester. I'll check. Thanks

 

[juno pierrat]

i'm that guy that says" that happened to me", and i read its a new pump, anyway, turned out to be diaphragm in fuel pump leaked back into crank case. remove pump with lines still attached, pump primer bulb, if fuel come out small in back of pump, diaphragm bad, ( fuel will probably leak between halves of pump because not clamped tight like when in place), the only reason i checked was because local shop said maybe getting to much fuel.

 

[Itsallalie]

Will do. Thank you

 

[Itsallalie]

Sounds like it might be running on 1 cylinder at times.----Does spark jump a gap of 3/8" or better on a test device.----Sparkplugs are NOT used during this maximum output test.

Both cylinders jump over 3/8".

 

[Itsallalie]

i'm that guy that says" that happened to me", and i read its a new pump, anyway, turned out to be diaphragm in fuel pump leaked back into crank case. remove pump with lines still attached, pump primer bulb, if fuel come out small in back of pump, diaphragm bad, ( fuel will probably leak between halves of pump because not clamped tight like when in place), the only reason i checked was because local shop said maybe getting to much fuel.

Pulled pump off but see no leakage past diaphgram so the mystery continues.

 

[racerone]

Part # of the pump that was installed ?----Was it mounted over the pulse port on side of top cylinder ?----Replaced plug leads ?-----Water pump impeller replaced ?----Compression values today ?

 

[juno pierrat]

is the armature plate under flywheel moving freely? may need cleaning and lube. if removing flywheel again , is there any dark goo under electrical items? and compression numbers are basic needed info

 

[oldboat1]

sounds like it's a spark problem at higher rpm, or an overly rich fuel/air mix. Run 50:1 for the oil ratio.

 

[Itsallalie]

Part # of the pump that was installed ?----Was it mounted over the pulse port on side of top cylinder ?----Replaced plug leads ?-----Water pump impeller replaced ?----Compression values today ?

omc PART # 0438556 Mounted on pulse port. Plug leads not replaced. Water pump 2 years old. 160#

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