1990 Johnson 15hp only start with carb disengaged

sinkingscones · Oct 23, 2024

Model: J15RESR
Previous owner couldn't get it to run, I cleaned carb, swapped plugs and wires, and replaced carb body cover which I found was cracked. Only thing left is cam roller missing a rubber sleeve I haven't fixed. Running 50:1

With needle idle set at 4 turns out and choke engaged (butterfly closed) I can't get it to start. It'll only start with the choke disengaged (butterfly wide open).

I'm wondering if it's running too rich, not sure what to check next.

Crosbyman · Oct 24, 2024

what cleaning did you do on the carb.....sprayed carb cleaner or full take down and rebuild ?

sinkingscones · Oct 24, 2024

Crosbyman said:
what cleaning did you do on the carb.....sprayed carb cleaner or full take down and rebuild ?

I sprayed it down and put it back together, but also the plastic carb body cover was replaced since it was cracked so the idle needle and the cam barrel had to be adjusted.
Also while it's running on neutral with tiller twisted towards start, is it supposed to die off when I twist it back the other way?

Crosbyman · Oct 24, 2024

the other way being SLOW... yes some engine use the throttle to shut down some have a kill button... as long as it idles nide in gear you should be all set

seems to have IDLE STOP adjustments(Screw spring...) see parts diagram or user manual for adjustments or... wait for expert here to comment

racerone · Oct 24, 2024

I have learned ( long ago ) that trouble shooting on outboards starts with a compression test.-----Post the numbers here.-----Walked away with a low hrs 1964 model 5.5 Johnson from an---- AOMCI----meet.-----Half a dozen folks looking at it basically declared it SCRAP because of low compression on top and bottom.--------I said right there that the head gasket was blown.-----When I got it home I took the head off and there was the head gasket blown between cylinders.

jitterbug127 · Oct 24, 2024

4 turns out is too much. I've always started at 1 and 1/2.

sinkingscones · Nov 4, 2024

Crosbyman said:
the other way being SLOW... yes some engine use the throttle to shut down some have a kill button... as long as it idles nide in gear you should be all set

seems to have IDLE STOP adjustments(Screw spring...) see parts diagram or user manual for adjustments or... wait for expert here to comment

I have the red kill button at the end of the tiller hande so I'm assuming its probably not supposed to die when it's turn fully to the opposite end.

sinkingscones · Nov 4, 2024

racerone said:
I have learned ( long ago ) that trouble shooting on outboards starts with a compression test.-----Post the numbers here.-----Walked away with a low hrs 1964 model 5.5 Johnson from an---- AOMCI----meet.-----Half a dozen folks looking at it basically declared it SCRAP because of low compression on top and bottom.--------I said right there that the head gasket was blown.-----When I got it home I took the head off and there was the head gasket blown between cylinders.

I think they're close enough to not be a problem.

sinkingscones · Nov 4, 2024

jitterbug127 said:
4 turns out is too much. I've always started at 1 and 1/2.

4 turns out is the suggestion from the service manual but I've tried it all, it doesn't affect anything. Seems to be running too rich, spark plugs are wet and today it suddenly only starts with throttle open.

sinkingscones · Nov 7, 2024

Is this too much oil for 5 mins? Almost looks like a leak

saltchuckmatt · Nov 7, 2024

No.

In a barrel that's what they look like. What it wants is to be taken out on a boat.

OptsyEagle · Nov 8, 2024

"Only thing left is cam roller missing a rubber sleeve I haven't fixed. "

Without that rubber sleeve I would think you would be having problems synching the carb to the timing advance. Also, the throttle starting positions would be all messed up. I would fix that first. For a band aid fix I found that 1/2" pex pipe almost fits around that sleeveless carb roller perfectly. I took a round file and filed out the inside a little so the pex pipe fit better and held it on the carb with electrical tape and it has been working for me that way for 3 years now.

Anyway, I suggest you fix that and then make sure your carb is synced up by ensuring the line or arrow on the throttle cam is in the middle of that fixed roller just as the throttle cam touches the roller.

sinkingscones · Saturday at 5:19 AM

OptsyEagle said:
"Only thing left is cam roller missing a rubber sleeve I haven't fixed. "

Without that rubber sleeve I would think you would be having problems synching the carb to the timing advance. Also, the throttle starting positions would be all messed up. I would fix that first. For a band aid fix I found that 1/2" pex pipe almost fits around that sleeveless carb roller perfectly. I took a round file and filed out the inside a little so the pex pipe fit better and held it on the carb with electrical tape and it has been working for me that way for 3 years now.

Anyway, I suggest you fix that and then make sure your carb is synced up by ensuring the line or arrow on the throttle cam is in the middle of that fixed roller just as the throttle cam touches the roller.

View attachment 403346 View attachment 403347 View attachment 403348

That was a great idea! I finally got to it and it all looks good but the line is far right and it's not close to lined up. Can just line it up by adjusting the linkage or is there a more proper way to do it?

sinkingscones · Monday at 2:47 AM

Cam looks just slightly off to the right. Can someone confirm, it SHOULD be lined up dead center when the handle is at the START position and not SLOW? This is as far as I can twist the handle towards slow trying to line up and at START it's even further off being that it's already past the mark.

racerone · Monday at 4:42 AM

For starting you ignore the " start " on the throttle grip.------Turn the throttle till it hits the shift interlock.

OptsyEagle · Tuesday at 6:26 PM

I believe the line on the throttle cam should be in the middle of your roller when that cam just touches the roller. If it is off adjust the linkage until it lines up. Don't worry about where the throttle is saying it is positioned when doing that, just make sure the roller touches the cam at that line

After that, If it does not start when you set the throttle to "start" then turn the throttle more to give it more gas. Don't worry about positioning the throttle to the start position. Just turn the throttle to give it more gas until it starts.

sinkingscones · Wednesday at 3:01 AM

OptsyEagle said:
I believe the line on the throttle cam should be in the middle of your roller when that cam just touches the roller. If it is off adjust the linkage until it lines up. Don't worry about where the throttle is saying it is positioned when doing that, just make sure the roller touches the cam at that line

After that, If it does not start when you set the throttle to "start" then turn the throttle more to give it more gas. Don't worry about positioning the throttle to the start position. Just turn the throttle to give it more gas until it starts.

Okay so I just set the roller to line up center as it touches and looks good now. I've gone through the service manual and the part that it doesn't mention is how much range I should have from full "Slow" to cam/roller lining up. As of now there is zero range.

From the picture I posted few posts above, the roller is set centered to the cam but at the tiller arm it's maxed full slow so I can only go full throttle from there. From some videos I've seen, they have some space before cam/roller lining up.

So far your model look closest to mine so I'm curious what your range/cam position looks like full slow and full throttle in neutral.

Crosbyman · Wednesday at 7:26 AM

the roller is set centered to the cam but at the tiller arm it's maxed full slow so I can only go full throttle from there. ????

if the cam follower is centered on the mark the tiller should be at or close to START....works like that on all obs ... if you rotate the tiller to FAST the mag plate should move CCW and the cam will push the roller to max throttle .

if that does not happen (in gear) then something is wrong in the linkage or the mag plate is being stopped from rotating. Check that nobody messed with the tiller teeth match in the joint

racerone · Wednesday at 7:32 AM

I do not believe there are " tiller teeth " on this 1990 motor.-----It uses a cable set-up.-----But I do prefer the older model set-up.

sinkingscones · Wednesday at 7:35 PM

Crosbyman said:
the roller is set centered to the cam but at the tiller arm it's maxed full slow so I can only go full throttle from there. ????

if the cam follower is centered on the mark the tiller should be at or close to START....works like that on all obs ... if you rotate the tiller to FAST the mag plate should move CCW and the cam will push the roller to max throttle .

if that does not happen (in gear) then something is wrong in the linkage or the mag plate is being stopped from rotating. Check that nobody messed with the tiller teeth match in the jointView attachment 408152

In gear and full throttle, the butterfly is wide open no issues there. My concern is the other direction doesn't have as much range. I found another thread where OptsyEagle mentioned at some point toward slow, the cam roller moves off which isn't my case right now. I will be adjusting the linkage and see where that gets me.

In neutral I have about less than a half inch range shown in the pic which is really just the slack from point of cam/roller lining up and hitting the stop towards fast. Makes me think someone shortened the range from fast-start-slow to just fast-start.

Also racerone is correct that it is cable only.

1990 Johnson 15hp only start with carb disengaged

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