97 Johnson 50hp 3cyl - idle problem

[bleb]

Hello
I've had this outboard since new and it's never really given my any problem until the past year when it started to quit at idle. It would start ok and once warmed up when I'd bring the fast-idle (or whatever that's called) down it would idle for a minute or two and then quit. Restart would be ok but basically as soon as it was moved back to idle it would likely quit (not always but mostly)
Once moving it would be fine and to top speed was the same as always, sounds fine, etc etc etc but I slowed down to idle, say pulling into a dock, it would most likely quit.

I took it to a local mechanic who was recommended for outboards to do a "tune-up" and once over, he called and said the compression was too low and that was preventing the fuel from being pumped (delivered) at idle and it wasn't likely worth rebuilding rings, bearing, etc.
When I picked to boat back up he said the compression was pretty even but 110 pounds.

ANYWAY, looking for any suggestions for a way to limp through the season somehow and was wondering if there was a way of bumping the idle rpm a little bit but still letting it be shifted out of neutral or well pretty much any input at all.

Thanks

 

[Crosbyman]

can you try to open the LS adjusting screw a bit and run with a good Engine cleaner product to see if the LS carb circuit of the engine reacts at all.

could be just the idle needle crudded up a bit .

better yet ... remove it completely, count the turns and note it down.
get a can of carb cleaner and blast it in the LS needle channel (wear eye protection)

reinstall needle at the same turn count.

get a compression meter or borrow one and measure the compression yourself.... no hard to do !

 

[racerone]

Pull the cylinder head and inspect.-----Quick and easy.----Only costs a new head gasket.---You will learn a lot.

 

[tphoyt]

Agreed
I personally would be suspicious about the low compression theory.

 

[bleb]

Thanks, I'll try the needle bit first and I've got a compression tester (car guy who knows very little about 2 stroke boat motors). I'm going to be playing with it next week sometime and I'll check on the numbers myself as well as try to find a source for part / gaskets (and a head gasket as that sounds like a good second step.

 

[bleb]

Agreed
I personally would be suspicious about the low compression theory.

How do you mean? Again I've got virtually no experience with the workings of a 2 stroke other than some minibikes back in the 70's

 

[Crosbyman]

easy stuff first !!
....Once moving it would be fine and to top speed was the same as always, sounds fine, etc etc etc

 

[bleb]

Not sure if it is in any way related but the motor used to (last year, maybe the year before as well) sort of buck when at idle, not quit just sort of give a buck every few minutes or so, like a random misfire, you could see the motor give a little kick to the side

 

[Crosbyman]

How do you mean? Again I've got virtually no experience with the workings of a 2 stroke other than some minibikes back in the 70's

some shops find problems.....

Ronald Reagan.. "trust but verify" !!

 

[bleb]

some shops find problems.....

Ronald Reagan.. "trust but verify" !!

LOL, I was thinking the other way, this old guy is very busy and I kind of thought he just didn't want to get any deeper into it.... He's the one who said it wasn't really worth spending any more $$$ on it.

 

[Crosbyman]

he should have just said so and not give you false opinions

anyway do the easy stuff

 

[bleb]

He's certainly a different cat (but did come recommended for older boats so that's how I ended up there)
Anyway enough of that, I'll check the compression myself and while the plugs are out stick a scope into the cylinders and see if anything leaps out, then have a go at cleaning those needles / seats up and see if that does anything and report back here with some details.
Thanks to everyone for the suggestions
B

 

[flyingscott]

Your motor has decompression holes, 110 is not that bad for your motor. I would look at the quick start and for any broken or worn linkages.

 

[rowerowe101]

Hello
I've had this outboard since new and it's never really given my any problem until the past year when it started to quit at idle. It would start ok and once warmed up when I'd bring the fast-idle (or whatever that's called) down it would idle for a minute or two and then quit. Restart would be ok but basically as soon as it was moved back to idle it would likely quit (not always but mostly)
Once moving it would be fine and to top speed was the same as always, sounds fine, etc etc etc but I slowed down to idle, say pulling into a dock, it would most likely quit.

I took it to a local mechanic who was recommended for outboards to do a "tune-up" and once over, he called and said the compression was too low and that was preventing the fuel from being pumped (delivered) at idle and it wasn't likely worth rebuilding rings, bearing, etc.
When I picked to boat back up he said the compression was pretty even but 110 pounds.

ANYWAY, looking for any suggestions for a way to limp through the season somehow and was wondering if there was a way of bumping the idle rpm a little bit but still letting it be shifted out of neutral or well pretty much any input at all.

Thanks

Compression shouldn't effect fuel delivery unless your pump is powered by crank case vacuum. Do you have electric pump or manual? But ya, I would suspect the carbuerator first, ultrasonic cleaning is best imo.

 

[racerone]

Has the motor been stored with fuel in carburetors in the off season ?------Fuel pumps are driven by crankcase PRESSURE on these motors.-----Need to look at adjusting low speed mixture.----Bumping up the idle speed with stop screw.-----

 

[bleb]

Has the motor been stored with fuel in carburetors in the off season ?------Fuel pumps are driven by crankcase PRESSURE on these motors.-----Need to look at adjusting low speed mixture.----Bumping up the idle speed with stop screw.-----

I've never drained it so I'll go with yes.
Typical was a bunch of stabilizer in the tank on the last outing, drain and change the gearcase oil, disconnect the fuel and oil lines at the motor, remove the plugs and spray some storage oil into each cyl and turn it over a few times, put the plugs back in finger tight and wrap it up.

 

[bleb]

Had a bit of time this afternoon so thought I'd check the compression to see what it actually is.... All I found out is that my old compression gauge seems to be toast. Need to borrow one from one of my buddies and try that again

 

[bleb]

Rain finally stopped so I managed to get the compression tested. 110 pretty much right on the top and bottom cyl, the middle cyl is just a line thickness under so 108ish
Checked spark on each coil, seems strong
Took each low-speed needle out, all of them seem clean but I wiped each down and sprayed into the seats several strong blasts of carb cleaner, let it soak a bit and repeated. But then it started raining again so that's as far as I got.
Needles were at 3/4 out from seated, book says 1-3/4 but that might have been the mechanic guy playing with them.
Need to find a barrel to cut in half to set the motor in to start it up, can't pour that much water where it sits to run with muffs on.

 

[bleb]

ok so some progress. Managed to get a tank large enough for the motor.
Needles are set at factory 1-3/4
Engine pretty much does what it's been doing, possibly a bit worse
In the start-up throttle the motor will start and rev up but once it's warmed up and I back the throttle down and it quits.
I can't get an idle timing value since I can't get it to idle forget about idle in gear but it looks like it's pretty close if I look at how much advance is still left to take out and check at about 1200rpm it seems to be about where it should be.
The idle stop is all the way in and doesn't contact the arm so I'm not sure where to set the idle. The turnbuckle on the cable is the only other adjustment I can see, There's no mention of that in my manual that I can find.
The "bucking" is still there at low speed and if anything seems worse but it's a lot different comparing the motor in the lake vs in the yard with all the covers removed.

Anyway, what's my next step?
Thanks

 

[bleb]

Disconnected the throttle cam and cranked the cable adjustment in (extended the side going to the timing throttle lever so the timing stays in more at idle) and then brought the rod-end to the cam back 5 turns so that the cam isn't touching the roller and the engine will run there but still only about 850rpm, if I bring the timing back out any more it drops and quits.
Backed the 3 idle screws out one at a time, 1/4 turn at a time and let it settle, (doesn't actually change a whole lot) to get what seems like the highest idle (top one came out 1-1/4, middle about 1 and the bottom about 3/4)

The engine will start again right away, sometimes just turning the key, sometimes I have to bring up the throttle a bit for it to restart, and then it revs way up and I need to drop it back down. (almost like it might be flooding?)

Thought?