1977 Johnson 55HP starting problem

[CobisCaller]

Hello

I have owned this motor for a couple years and have used it minimally. The previous owner said it had an intermittent starting issue. I ran it a few times last season and started it several times last season in the garage with muffs on and it seemed to fire right up most times. Last fall I had it out on the lake and it started and ran fine and then started bogging down at WOT. It only seemed to be going about half speed or so with the control all the way open. It would occassionally rev up to full speed and then slow back down. That was the last time I used it last fall. Over the winter I would occasionally put muffs on it in the garage and it would start okay.

This spring/summer I started it with the muffs on and it started fine each time.

I took it out to the lake tonight with the hopes of narrowing down the problem. I put it in the water and it fired right up. Idled kind of rough (kind of "popping") for about 5 minutes but kept running. I took it out on the water and it ran good at WOT for a couple minutes and then bogged down, only running about half speed. I slowed it down and it would rev up a bit and then back down. I put it in neutral and it died. Tried starting it several times and it would fire a little but not run. Then not firing at all. I put on a spark tester on both cylinders and each lit up. I let it sit and checked the linkages and nothing obviously wrong. Tried starting it a couple more times and it finally started. Still a little rough idle but it was running. Went right to WOT and cruised around fine for probably 15 minutes. Backed off the throttle on the way back to the ramp and it seemed like it wanted to die if I got too close to neutral. Got close to the docks, and slowed it down and put into neutral.
It died. Tried starting it several more times at the dock and nothing. Put it on the trailer and hauled it home.

Not sure if the WOT issue and starting issue are related but hoped to get some advice on a starting point. I kinda need it to start reliably in order to see if I'm losing spark or what at WOT. Any help would be greatly appreciated.

Thanks

 

[ondarvr]

Clean the carbs.

 

[Joe Reeves]

Good explanation of problem.... The carburetors do sound like they need cleaning... BUT... before jumping in that direction, do the basic trouble shooting.

Remove the spark plugs.
Compression: What is the compression psi of all individual cylinders?
Spark: The spark (with all s/plugs removed) should jump a 7/16" gap with a strong blue lightning like flame... a real SNAP! Does it?...... Check this on a cold engine and also when hot with the problem being present if possible.

What spark plugs are you using.... make, heat designation, gap setting?

(Spark Tester - Home Made)
(J. Reeves)

You can use a medium size philips screwdriver (#2 I believe) inserted into the spark plug boot spring connector, then hold the screwdriver shank approximately 7/16" away from the block to check the spark or build the following:

A spark tester can be made with a piece of 1x4 or 1x6, drive a few finishing nails through it, then bend the pointed ends at a right angle. You can then adjust the gap by simply twisting the nail(s). Solder a spark plug wire to one which you can connect to the spark plug boots, and a ground wire of some kind to the other to connect to the powerhead somewhere. Use small alligator clips on the other end of the wires to connect to ground and to the spark plug connector that exists inside of the rubber plug boot.

Using the above, one could easily build a spark tester whereas they could connect 2, 4, 6, or 8 cylinders all at one time. The ground nail being straight up, the others being bent, aimed at the ground nail. A typical 4 cylinder tester follows:

..........X1..........X2

.................X..(grd)

..........X3..........X4

Let us know what you find.

 

[CobisCaller]

Hey thanks for the responses. I hope to dig into this this weekend.

As far as the carbs go, when I have them disassembled, is there any thing I should look for to know if I should be replacing any parts? I read the link about running wire through the jets and blowing out with air. Just wasn't sure if I should replace anything while I have them apart.
I plan to get a compression tester and check that first. Then check the spark gap and the plugs like you recommended.
I will report back with what I find on those two things.
Thanks again.

 

[CobisCaller]

Okay I got a compression gauge today.
As long as I'm doing this correctly, here is what I found.
Removed both plugs. They are the correct number. The top plug looks "good", but the lower one definately is burning different. There is a black carbon looking coating on the electrode.
I get about 110psi on the top cylinder and maybe 10 psi on the bottom cylinder. When I plug the bottom cylinder with my finger and rotate the flywheel I can feel decent suction but very little pressure out. If i partially uncover the hole, i can hear air push out, but the upper cylinder definately has more pressure by feel.

Soooooo, what would you recommend next?
Is there an exhaust valve or something stuck open? Like I said, the problem seems to come and go.

Thanks
Josh

 

[Joe Reeves]

With 100 psi compression difference between cylinders, remove the cylinder head to inspect the piston, cylinder wall, sealing surface of the block and head, the head gasket, and the dome of the head.

 

[ondarvr]

Is there an exhaust valve or something stuck open? Like I said, the problem seems to come and go.

Thanks
Josh

​You have a 2 stroke, there are no valves.

If you're lucky it could be a head gasket, not so lucky and the piston and rings are toast.

 

[CobisCaller]

Okay I got the head off today and the gasket looks okay. Unfortunately the piston ring looks to have gone bad.

The cylinder wall is scored in a couple places at about 5 o'clock and 7 o'clock. The upper piston wiggles a bit but the lower one definately feels looser. The lower piston has a little carbon colored coating on it also.
The dome of the cylinder head has a bunch of little "pits" in it, while the upper one is smooth and shiny.

I now realize I have some major problems.

1. Is this motor repairable?
2. Is this model of motor worth rebuilding in the first place?
3. If so, at this point what would I be looking at as far as a parts list goes? I would like to determine a dollar amount for parts alone.
4. Is the pitting of the top of the cylinder head a problem? I'm guessing that can't be machined and would need replaced? Not sure if this part is available for purchase.

Thanks for the advice so far.
I don't have much invested in the motor thus far, so I am willing to put some into it. Just not sure what I would be looking at.

Thanks again.
Josh

 

[CobisCaller]

To add. I bought this from the original owner of the motor. It was their family boat since new and I was told the motor had been rebuilt by a "competent" outboard shop at some point during its life.
Not sure if that matters as far as what parts may need replace, but thought I should mention the history that I know of.

 

[ondarvr]

Those "rebuilt at some time" stories are frequently hearsay from someone that doesn't know anything about motors not understanding that all they did was rebuilt the carbs.

​It can be rebuilt, but I hate rebuilding old motors because at that age the entire motor is past it's prime and many other components could be expected to fail at any time. And for the cost of a rebuild you could upgrade to decades newer technology for the same money.

 

[CobisCaller]

Does anyone have a link to a past thread on rebuilding this type of motor? I thought I saw a reference to one awhile back but can't seem to find it now.