1977 Johnson 55hp half speed?

[Pann Mann]

I have a 1977 Johnson 55hp outboard. I have replaced almost everything on it and it runs fairly well.

New:
coils
plugs
powerpack
fuel filter
fuel pump
complete carb rebuild (duel)
water pump
gear oil
fuel

I can start it and get it to idle pretty well. Dies a few times at low idle but needs more adjustment. The real problem is that when I have the throttle maxed out the motor only goes about 1/3 to 1/2 speed.

When I run it out of water with the rabbit ears hooked up the engine revs high and sounds good. However, under a load while in the water I cannot get it up to speed.

I have not adjusted it too much yet. I synced the carbs per manual including the linkages.

My guess is that I need to do more adjustments and maybe there is a lack of fuel but I am not sure. Any advice would be helpful. I am going to be working on it for the next few days trying to get it to go faster. My guess is that it is only going 10-15 mph

Thank you in advance

 

[1983 ercoa 21']

You can tell if it's getting full throttle by putting the controls at wotand looking to see if the butter fly's are open all the way and timing base it at it's stop without having it started

 

[racerone]

You should do a compression test before doing any more adjusting !!!

 

[Pann Mann]

Compression is good. Did that first when I bought the boat.

"You can tell if it's getting full throttle by putting the controls at wotand looking to see if the butter fly's are open all the way and timing base it at it's stop without having it started"

Not sure what the underlined phrase means. I know what the timer base is but can you clarify? Thank you.

BTW I changed the pump to keep the head cool. I adjusted the floats which were not level. I did not know to adjust them during the rebuild. I also found a few more throttle adjustments in the book and took care of those. I now need to give it a test run in the water.

Still need to do what Chief Petty Officer suggested concerning the throttle. Results will be posted.

 

[Chinewalker]

Also, do a cylinder drop test. Remove and ground one plug wire at a time and see how the motor runs. It sounds like you're only running on one cylinder.

 

[Pann Mann]

UPDATE-

Tested compression = 140 at each cylinder

Adjusted carburetor (floats needed adjusted and linkages also

Adjusted idle

RESULTS-

During a lake test the motor starts and idles great

While idling and in neutral I can rev the engine up manually and it really screams. The way it should while it is at full throttle.

However, while in gear it functions and drives forward and reverse but at full throttle the speed is not that fast. My guess is that it is at about half speed.

It seems like while under a load it is slower. I have watched youtube videos of 55 hp johnsons on the lake and their boats go way faster than mine.

Mine it attached to a 1979 Glastron tri-hull 14 foot.

Also, there is some hestitation with the motor while in forward gear. Sometimes it does not throttle up immediately and maybe will die, but only in forward gear.


As far as doing a cylinder drop test - that sounds confusing and I thing it is running on both cylinders. While in neutral is sounds really good and revs up to full speed.

BTW I checked the butterflies to see if they were all the way open during full throttle and they are.

Any suggestions are welcomed.

Thanks

 

[Michawilden]

If you run the engine with muffs on and rev it. It will rev up very easy. even though it could be running on one cylinder. However, under load, this will cause problems. I would also do the cylinder drop test on the water. Running on one cilinder can also explain the fact that is hesitates when you put it in gear.

 

[Pann Mann]

Can someone explain how to do the cylinder drop test? Some easy instructions. Chinewalker suggested I "Remove and ground one plug wire at a time and see how the motor runs." I am not sure exactly how to do this.

I did notice when I pulled the plugs that the top cylinder plug was not clean like the lower. They are new plugs but it was wet with fuel.

Thank you.

I did replace the power pack, both coils and the plugs. I was suspicious about the spark from the beginning and the electrical components under the flywheel. The timer base, I believe, seemed to be worn, but I could not tell for sure. Especially since I got the engine running.

 

[Chinewalker]

Cylinder drop test. Start and warm up the motor. Turn it off. Remove one plug wire from one plug and stick it on a head bolt. This allow the wire to arc to the bolt (if it is, in fact, sparking). Start the motor. If it doesn't start at all, you MAY have found that the motor is not running on the cylinder still hooked up. If the motor did start, turn the motor off and plug the loose wire back onto its plug. Remove the other plug wire and repeat the start & stop procedure of the first one. Do these tests on the water. It may be necessary to run the motor in gear during both cylinder tests as the cylinder may in fact be firing at idle revs, but not at higher revs.

 

[Pann Mann]

Chinewalker-

Your suggestion worked. I drop tested the cylinders and found one wire with no spark. I swapped some parts around to see if I could figure out why. My conclusion is that one of the new coils I replaced is faulty. I can swap coils and the other cylinder will work. This really threw me off because both coils are new. I ordered a coil and when it arrives I will install and update.

Thank you team for getting me on the right track and fast.

Pann Mann

 

[Pann Mann]

Final Post and Recent Update

Problem solved. I replaced the coil and immediately had both cylinders firing. I was refunded for the faulty coil I was sold. The engine idles perfectly, starts on the first try, and runs like a top.

Thank you all for your expert advice. I really could not have done it on my own without your expertise. I am sure I will chat with you all later.

Happy boating and tight lines.

Pann Mann