1983 Johnson 75hp, completely out of ideas.

[DWP]

Ok, I'm writing this on my cellphone so please ignore any grammatical errors. I have a johnson 75hp that is being a total pain in my *** and is one more part away from the bottom of the gulf. My problem is just general bad running motor, sometimes idles in the water, sometimes dies at idle, boggs under acceleration, hard to start when it gets warm. Just an overall slow response motor that can't be trusted, I've had to paddle in about 4 times in the last 5 trips, I've hired a mobile mechanic to look at it and I swear he gave up today, after taking my money of course.... Things I have done, cleaned all 3 carbs at least 3 times, 2 rebuilds on all 3. I've put on all 3 new coils, plugs wires etc, (firing blue spark), compression test 120 120 116, bought an external tank super clean ethanol free gas. Ran all new fuel lines. Still giving me nightmares... I have not changed the fuel pump, nor have I had the chance to run a timing light, I have however lynx and synced the thing so many times I should have a certificate. I've even gone as far to inspect the reed valves and they all look like they are in fantastic shape (I've ordered a new set anyway and will be installing thursday. I've gone over the whole.fuel system everything is striped.up nice. PLEASE help me. Ask any questions you like, lets get specific, I can't afford a new motor, and I can't enjoy the water constantly worrying about this haunted motor... I've also changed the waterpump just because I assumed it needed it... I noticed tonight after my breakdown/limp in ride today that if I blow air back through the bulb toward the tank I can pass air through the bulb into the tank with just alittle.preasure, I didn't know if that was worth mentioning. The trout will be running soon. so.again I beg. Please... Help me.

 

[BonairII]

Re: 1983 Johnson 75hp, completely out of ideas.

Make sure that your timing is advancing smoothly. Are you sure that you did the link/sync correctly?

Not a bad idea to replace the bulb.

From this point on....don't throw parts at your motor until you confirm that the suspect part is indeed bad.

 

[newlogics]

Re: 1983 Johnson 75hp, completely out of ideas.

I doubt I can point you to anything specific to your motor, but speaking from an extensive bike motor experience, I would have to point you to carbs. I've dealt with this more than once, when carbs are fully cleaned, rebuilt and seemingly perfect, but the motor would just not behave. Swapping for a different set of carbs known to run well all of a sudden makes the motor run perfect. If you're out of ideas on this, see if you can borrow a set of known good carbs and swap them in. If your issues continue, your search area becomes much smaller. If not, well, you know what to replace.

 

[mark1961]

Re: 1983 Johnson 75hp, completely out of ideas.

Has this thing ever run any good and if so what's changed since then?......Are the issues you are currently having intermittent?


Btw, what plugs are you running in it?

 

[DWP]

Re: 1983 Johnson 75hp, completely out of ideas.

I promise, no more parts. Other than the bulb. I am following the link and sync from the manual, I do not know where I.well find another set of carbs, I'm afraid that does not seem.like something I would be able to come across, I'll get the plug info in the morning. a note on the carbs, I have used the ole rag trick on then covering the intake on each carb to make sure they aren't clogged. it.ran well until about 2 winters ago, I drained the carbs and covered it up for the winter. Ever since its been like this. Last season was wasted on a busted foot.

 

[mark1961]

Re: 1983 Johnson 75hp, completely out of ideas.

I have used the ole rag trick on then covering the intake on each carb to make sure they aren't clogged.

That method wouldnt convince me the carbs are clean.....if you are truly sure they were clean when you bolted them back up any contamination would be coming from elsewhere.....have you checked the screen in the pump?.....are you running any other filters or water separators?

 

[DWP]

Re: 1983 Johnson 75hp, completely out of ideas.

That method wouldnt convince me the carbs are clean.....if you are truly sure they were clean when you bolted them back up any contamination would be coming from elsewhere.....have you checked the screen in the pump?.....are you running any other filters or water separators?

The carbs were spotless when bolted on, I looked at the screen in the fuel pump just last night. Clean. Sparkplugs are
L77JC4 Champions.

 

[DWP]

Re: 1983 Johnson 75hp, completely out of ideas.

Does the same trick work with boats as it does witg cars if you spray carb cleaner around the carbs and see if it revs up to pinpoint an air leak? Lets say these carbs are old, even though they were all just rebuilt. What exactly would I be looking.for? Fuel leaks? I'm not convinced its a fuel problem, but until I really.know something I won't rule anything out. Any way to preasure test the lines?

 

[AlTn]

Re: 1983 Johnson 75hp, completely out of ideas.

have you ever done a decarb procedure on this engine?..look under the Top Secret Files if you're not familiar with it

 

[danoutbard]

Re: 1983 Johnson 75hp, completely out of ideas.

What about a spark test ? A good spark should jump a half inch gap.

Sometimes, a bad cylinder can still give an apparently good cmp reading.

 

[DWP]

Re: 1983 Johnson 75hp, completely out of ideas.

Ill look into decarb, and passes a spark test with flying colors.


Also I feel it might be worth.mentioning that if in the event.i can creep it up step by step at about 1/2 throttle the engine will catch.up in a hurry and run wot without issues. Ofcourse if I come of the throttle and stop its the same madness again like rolling the dice with the ability.to get there.

 

[mark1961]

Re: 1983 Johnson 75hp, completely out of ideas.

Have you removed the core plugs at any stage while cleaning the carbs?.....Are you sure all the low/high speed orifices are where they belong?....Is the low speed circuit of the carbs adjustable (needle valves) or non adjustable (plugs)?....If they are adjustable what did you set them at after rebuild/tune?

 

[DWP]

Re: 1983 Johnson 75hp, completely out of ideas.

Have you removed the core plugs at any stage while cleaning the carbs?.....Are you sure all the low/high speed orifices are where they belong?....Is the low speed circuit of the carbs adjustable (needle valves) or non adjustable (plugs)?....If they are adjustable what did you set them at after rebuild/tune?

They are non adjustable, the freeze/core plugs were replaced the 2nd time they were rebuilt, I went more extensive when the simple soak and blow yeilded no real improvements.

I'm doing the decarb today, grabbed my seafoam and sparkplugs and am about to had back to the house.


Quick update. Decarb did not help my situation much at all. I have a friend coming tonight to check the timing.

 

[glenn property of pam]

Re: 1983 Johnson 75hp, completely out of ideas.

have you taken a good look at the choke (more off a fuel bypass valve that makes the motor run rich for starting). does it click when you press in the key? (if it doesnt it maybe because its already open). hard to start when warm is normally to much fuel. the reason i think this could be your problem is if i accidently push my key in to start when warm then my 84 70hp punishes me every time

 

[Daviet]

Re: 1983 Johnson 75hp, completely out of ideas.

Just a few thoughts.
All it takes to make your engine run is, timed spark, compression and fuel.
By the numbers you have for compression, I would think you are OK there.
The spark should jump a 7/16" air gap and be bright blue. You said it was OK.
Fuel is all that is left. Use a squirt bottle and squirt fuel directly into the carb with the engine running and see if all the cylinders will fire off correctly.

 

[DWP]

Re: 1983 Johnson 75hp, completely out of ideas.

Quick update, the choke solenoid is functioning properly, I tore the fuel pump down no tears or holes rechecked all those lines while I had it off, my friend brought me the timing light then bolted, only using these on cars before I went ahead and checked all spark with them, everything seemed legit, the motor idles on muffs at around 2300 that felt high to me so I tried to being it down between 1200 and 1400 when I did this it just starts sputtering and dies every time I got below 2000ish (rpm) I thought that was odd, but I'm not sure what to think of it. Just for the record I have never in myyyyyyy entire life had a problem this elusive and all around pita. The motor idling (at around 2300) showed to be just hardly.advanced past tdc, I would say 2 degrees max, but from what I remember you want to set the timing at wot for these, just for info sake the motor calls for 19 degrees, today when I did the decarb I was spraying seafoam into the carbs and they were responding correctly as far as acting choked and the idle would drop. What are the odds I could have an intermittent electrical problem that acts up under motor vibration? I could check my power pack. I'm out of ideas, completely.

 

[BonairII]

Re: 1983 Johnson 75hp, completely out of ideas.

Hook up the timing light and try to lower the rpm by manually retarding the timing....see if you're losing spark.

Out of curiosity...could timer base be shorting out when it rotates back to retard timing?

Just throwing some ideas out there... at this point you(we) need to start thinking outside the box.

 

[DWP]

Re: 1983 Johnson 75hp, completely out of ideas.

You might.think its outside the box but I swear.i saw the timing light "skip a beat" here or there at low idle just before it would spit and sputter, after that happened it would.never really catch up and eventually die, at higher rpm I never saw the sputter but I thought it might hide itself well. I am definately leaning toward electrical issue, intermittent. Or only effecting me under load or at low idle, it all kida fits too, runs well in the yard, higher rpm on muffs, when its in the water, rpms drop under load and it starts acting up, I feel like we are so close.

 

[BonairII]

Re: 1983 Johnson 75hp, completely out of ideas.

Sounds like it's time to break out a peak voltage meter(or dva adapter) and check your PP,stator, and timer base.

I'll be of no help in that regard, though cause I haven't done it before.

Can you test with the timing light on the water? Because of the high idle rpms, you may need to start the motor in gear(have someone else drive the boat) and see if you lose spark under load.

 

[DWP]

Re: 1983 Johnson 75hp, completely out of ideas.

My main question is, do I lose spark under load, or do I lose power because of no spark. Or is something weak on the electrical end that does not function properly at correct idle. Magneto etc...