2000 Johnson 50 hp engine surging

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Chuck Gibson

Petty Officer 2nd Class
Joined
Apr 13, 2005
Messages
123
I'm back again begging for you guys to help me.
My engine inconsistantly surges. Today I took it out and drove it for a few hours. It ran great through most of the day. Then for no apparent reason while opening up the throttle, it started surging and bucking. Letting off of the throttle to about half speed it still surges just not as violently. At that point, when you drop it back to idle, it smooths out and runs great. It is not consistant. Sometimes after it started surging, you open the throttle, and it runs great again.
I bought the boat several months ago. It had been sitting in a mans shop for years. I pulled and rebuilt the carburetors, replaced the leaking primer solenoid, drained the old fuel and replaced it with fresh gas.
I read elsewhere on this forum that sometimes the gas lines would get contaminated and cause problems. I bought a new gas line and will replace it tomorrow. I just want to pick you guys brains and ask what else I might look for..
Thanks for any ideas you can give me!
Chuck
 
R

racerone

Supreme Mariner
Joined
Dec 28, 2013
Messages
37,820
Model # of this motor ?---I assume a 2 stroke.-------Have you checked the gear oil ?------I know for a fact that these gearcases ( 2 stroke ) are not robust.------See if there are any metal bits on the drain plug magnet !!
 
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tphoyt

Lieutenant
Joined
Jun 10, 2010
Messages
1,260
Any chance of a video of this happening?
There are several things that are possible.
Fuel delivery, intermittent spark, gear case, motor mounted to high, damaged prop caveating and so on
 
C

Chuck Gibson

Petty Officer 2nd Class
Joined
Apr 13, 2005
Messages
123
racerone said:
Model # of this motor ?---I assume a 2 stroke.-------Have you checked the gear oil ?------I know for a fact that these gearcases ( 2 stroke ) are not robust.------See if there are any metal bits on the drain plug magnet !!
Click to expand...
Model # J50PLSSM. 2 stroke. I have not checked the gear oil, but I will. I'm really leaning towards it being a fuel problem because it seems like if it was the gearcase, it would be a consistant problem. That being said, stranger things have happened...
 
C

Chuck Gibson

Petty Officer 2nd Class
Joined
Apr 13, 2005
Messages
123
tphoyt said:
Any chance of a video of this happening?
There are several things that are possible.
Fuel delivery, intermittent spark, gear case, motor mounted to high, damaged prop caveating and so on
Click to expand...
No video. When I get the chance to take it back out, I will video the surging and get it posted on here. I'm in north Texas. Here lately, it is either raining or the wind is blowing 90 to nothing....Today we are getting 39 mph gust...
Fuel delivery and intermittent spark... How can I check for intermittent spark with it not being consistant? I'm sure there is a way, I just don't know how. It seems like it would have to be checked while it is surging... What could cause it to spark intermittently? Maybe I could check that.
 
C

Chuck Gibson

Petty Officer 2nd Class
Joined
Apr 13, 2005
Messages
123
racerone said:
Hook up a timing light.----One cylinder at a time.------you want steady flashing of the light.
Click to expand...
Duh..... I feel stupid! lol. The sad part is, I have worked on old school cars for years. Why didn't I think of that. I tend to overcomplicate things...
Thank you so much for the lesson in common sense. I will probably need a lot more of these lessons before I get this boat running! lol

PS. That will also make it easier to check while surging across the water!
 
C

Chuck Gibson

Petty Officer 2nd Class
Joined
Apr 13, 2005
Messages
123
OK. I changed out my fuel line and found "A" problem. I don't know if it is "THE" problem, but regardless, I found that part of my fuel line had separated on the inside. I will get on my phone in a few minutes and see if I can post a picture of it. I started it in the driveway and it seems to be running ok. I don't know how it will behave once it gets a load on it in the lake. I hooked up a timing light on it and it does not seem to have intermittent spark. I pulled the plugs and they are running nice and tan.
I did notice that when I slowly increase the throttle to about halfway, the engine increases evenly with the throttle. After a few seconds, it revs up quite a bit but it is a steady run, no surge. Is this normal seeing that the engine does not have a load on it?
 
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Chuck Gibson

Petty Officer 2nd Class
Joined
Apr 13, 2005
Messages
123
I tried to upload a video of it running in the driveway but it gets up to 29% and says it ran into problems and stops uploading...
 
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tphoyt

Lieutenant
Joined
Jun 10, 2010
Messages
1,260
That could very well be the problem. Is that the dreaded gray fuel line? May as well check your filters as well and if you have that same line after the filter and before the carbs you may have some debris in the carbs. Do away with that line and go for cruise.
 
C

Chuck Gibson

Petty Officer 2nd Class
Joined
Apr 13, 2005
Messages
123
racerone said:
Testing for power in the driveway is a waste of time.
Click to expand...
I agree. I changed the fuel lines and I wanted to make sure I didn't have any leaks and I also wanted to see if I had a firing problem. That's why I was saying that I didn't know how it would hold up under a load on the lake. I'm just praying my problem is solved...lol
 
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