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75 hp Johnson Stinger 1977

S

Siniscta

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New to this thread hoping for some help. My 1977 75hp Stinger runs awesome for about an hour then the fun starts! When I try to accelerate past idle it gets to a point where it starts to bog down and stalls. If I slip it back into idle before it dies it will idle great. Well....I go between idle and go for awhile and eventually she’ll take off and run great. I put 40 miles on the boat this weekend doing that process. It did it last year so I rebuilt the carbs, replaced fuel pump, gas lines, plugs, and primer bulb before taking it out this year. It had a bit more spunk but this problem never went away. It has spark. I ordered a PVA but I’m confused on how to thoroughly check the ignition system. The service manual talks about testing ignition with a neon tester. I can’t find specs. either. I guess I just need something that outlines the process for a beginner. Any help would be appreciated. Thanks!
 
If pumping the fuel primer bulb constantly by hand, acting as a manual fuel pump, causes the problem to cease... the cause of the problem would be in the fuel system, not the ignition system (faulty fuel pump?), however...........

Do a close visual check of the stator under the flywheel. If it should be dripping a sticky looking substance down on the timer-base and powerhead area, that would indicate it has encountered a meltdown problem. That would result in a AC voltage drop to the powerpack capacitor which, in turn, when hot, would result in weak, erratic, and eventually no spark.

A stator in the early stages of this type failure may very well function properly when cold, but when hot loses its voltage production power.

Also, check the timer-base to see if it has a tendency to stick, more likely to take place when the engine is hot rather than cold... BUT... when cold is also possible.

Fouled carburetors will also result in having the engine fall on its face, so to speak... BUT... carburetors do not come and go, back and forth. If they're faulty, they stay that way... so this being the cause is unlikely.
 
Did a compression test and it looked good. Used new gas tank with new fuel lines and bulb. Replaced impeller 3/4 years ago and motor pumps water through good. I have spark. Did the ol primer bulb thing when sputtering and that did t help. I rebuilt carbs. I’m pulling the flywheel today to look around. Thanks guys I’ll keep at it
 
fdrgator said:
What joe said, check for sticking timer base.
Click to expand...
Hooked an in-line spark tester to motor and set the gap at 7/16 boat fired right up and idled great Did this for all 3 plugs. Just idled for awhile didn’t let it run for loung. Spark seemed strong. I guess I’ll pull flywheel off tomorrow
 
Ok. I’ll do it again in the morning. Thanks. Can anyone tell me how to test the power pack. I do have a DVA adapter. Just don’t know what the heck I’m doing!
 
Siniscta said:
What would cause the timing base to stick? Could it have something g to do with the play in the throttle cable?
Click to expand...

Usually due to someone putting grease on the nylon retainer... collects debris, creates binding... OR... a stator meltdown of dripping sticky stuff dripped on that nylon ring, that'll do it.
 
Removed flywheel. Everything looks good I think. How far should flywheel key stick out of crank. What is the torque on flywheel nut
 
The key only needs to stick out a little bit.------The key locates the flywheel for proper timing.-----The flywheel is driven by the crank / flywheel locking tapers.----That when it is assembled clean and dry with proper torque on the nut.----about 100 FT-LBS on the nut.
 
Install key as shown below. Nut torque = 105 foot pounds.
CS-FW_Key_Align.jpg
 
I'm following this closely. My 1984 3 hole Evinrude does the same crap as your motor and its driving me nuts LOL. I know it is not the fuel system. Its gotta be ignition. That motor is such a cream puff I was going to just replace it ALL. All that stuff is 35 years old. I'm interested in what you find though
 
The stuff is 35 years old.----This stuff is very well made and no need to replace it all " just because " ----some orderly testing can find the culprit every time !!
 
I was reading about that TSB sounds interesting. My boat is a 1977 though not a 76 that the TSB came out for. Is there a chance my carbs have that problem? How do I check?
 
Ok took a little closer look a timer base and those nylon fittings look greasy and old. Where can I buy those. Is there a part number
 
I don't believe that anyone addressed your DVA diagnostics procedure question. Go to the CDI Electronics, free on-line service manual and follow specific testing instructions. When testing the "trigger/timer" be sure you try ALL THROTTLE POSITIONS. If you run without cowling in place are the symptoms minimized. Then we have to direct our attention to electronic components reducing spark strength when HOT! When it drops power, does it come back when you pump up the primer? Mr. Scott will love this next question. Did you, or the previous owner ever use ethanol fuel? What state do you buy your fuel? What is a "neon" tester? Not applicable for your old Stinger, I don't think. I'm working on one here right now.....EXACTLY what you have, but compression is only 110.
 
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