1976 Johnson 70hp timing/high idle issue

[jadoty]

Had this boat three months and idle was set really high when I got it. 2500-3000 RPMS in neutral and 2000-2500 idle in gear. Rebuilt the carbs and tried to link and synch to set the idle down - it still won't idle at less than 2500 rpms in neutral in tank - sneezes back at less than that. I understand it will run at less than that under load, but will still be way too high. My question is, assuming the WOT timing is off, which I haven't checked yet, will adjusting the WOT timing be likely to allow me to set down the idle timing, or should I be looking for some other issue here?

 

[Walker]

Re: 1976 Johnson 70hp timing/high idle issue

Make sure the timer plate is all the way against the stop at idle. Make double sure your link&sync is correct with just a hair's gap between the throttle pickup cam and the throttle roller. Check all three carbs to see that the throttle plates are in sync together and that they are fully closed at idle.
Iff all checks out try backing down the idle stop screw on the timer plate.

 

[jadoty]

Re: 1976 Johnson 70hp timing/high idle issue

I'm assume what you call "timer plate" is what I call the throttle lever, that is connected to the yoke/throttle cam. If not, I'm definitely confused. With that assumption, everything is as you said - throttle plates are closed, are synched, roller is aligned where it is supposed to be on the throttle cam and idle stop screw is against the lever. I failed to mention that at 2500 rpm, 'idle' timing is at TDC. If I back it down, timing goes way AFTER tdc, it begins sneezing back and eventually dies.

 

[Silvertip]

Re: 1976 Johnson 70hp timing/high idle issue

Flywheel key partially sheared giving you incorrect timing???

 

[jadoty]

Re: 1976 Johnson 70hp timing/high idle issue

Wouldn't that make the timing really erratic? I've checked it several times and it's exactly the same.

 

[jim_in_day]

Re: 1976 Johnson 70hp timing/high idle issue

Make sure the timer plate is all the way against the stop at idle. Make double sure your link&sync is correct with just a hair's gap between the throttle pickup cam and the throttle roller. Check all three carbs to see that the throttle plates are in sync together and that they are fully closed at idle.
Iff all checks out try backing down the idle stop screw on the timer plate.

Walker has it completely correct, I have a 76 Rude 70hp that I fought a bunch doing the same things you have. The thing with these 3 cyls is that idle timing at TDC is where you want the carbs to pick up. before that, from about 1100 rpm to the 2500 RPM at TDC is strictly timing advance, no carburator. If it can't idle down to 1100 RPMs by slowing down the timing, you are having a carb float setting issue and it is probably to lean at lower timing settings. I would take a real close look at where your float level is set, that motor is very sensitive to float setting (since the jets are fixed). Good luck

I edited this shortly after posting it because I went back and looked at your symptoms and it appears to be lean sneezing as you slow it down. Be careful, too lean will kill that motor quickly (thats why I'm doing a total rebuild on mine right now)

 

[jadoty]

Re: 1976 Johnson 70hp timing/high idle issue

Thanks for everyone's input - I didn't mess much with the floats when I rebuilt the carbs because they all looked parallel, but I didn't actually measure the 1/16th in. clearance, so I will check that again. The TDC timing at 2500 rpm still confuses me though. Maybe it's totally irrelevant, but I am interested to know where the WOT timing is set, so I may check it on the ramp. Is anyone familiar with the Joe Reeves timing method without the motor running?

 

[jadoty]

Re: 1976 Johnson 70hp timing/high idle issue

Here's a reference to discussion of exactly the same problem, in case it provokes any further thoughts. Apparently no solution, unfortunately.
http://www.outboardrepairs.com/topics/002962.html

 

[Theoutdoorsman]

Re: 1976 Johnson 70hp timing/high idle issue

jadoty.........maybe you could post a photo of your current link and sync to give everyone a birdseye view. It could possibly be a very simple fix if these guys could take a look at it. Is this a recent rebuild?

 

[Silvertip]

Re: 1976 Johnson 70hp timing/high idle issue

Wide open throttle timing is just that -- it affects ignition advance at WOT. If you've performed link & sync properly and set idle timing properly something is amiss in your carb rebuild or there is an air leak somewhere. Just as an aside, a sheared flywheel key does not generally cause erratic timing. It means the flywheel has slipped on the crankshaft. The fact that the engine is sneezing may be the cause of that. It may be totally sheared or partially sheared -- either of which will present incorrect timing readings. It's easy to check. Look at it. If you are making these adjustments without a service manual, check your local library. If its any size at all they generally have an assortment of them. They may not have the exact version for your engine but at least it will give you an idea of the parts involved, their purpose, and what effect the adjustments have.

 

[jadoty]

Re: 1976 Johnson 70hp timing/high idle issue

Unless the pointer itself is off, I don't think it is the flywheel key. The pointer is at TDC when cylinder No. 1 is at TDC. So I think the timing is right and it has to be a carb issue somehow. I did just do a rebuild because when the idle was originally so high, somebody told me the idle screws were plugged. But when I did the rebuild, everything was clean as a whistle. I did install three new idle screws anyway so I know that isn't an issue. Have Seloc, Clymers and the factory manual so I'm about 99.9% sure I've done things right. I didn't mention before that there was a blown head gasket in the middle of this process but I replaced it, and compression is good. Have redone the link and sync three or four times and I'm really back to where I was when I got the boat. Unfortunately no digital camera. When I said sneezing back I probably used the wrong terms - it was really coughing through the exhaust which I'm guessing was due to severly retarding the idle timing to get the rpms down, maybe firing on the down stroke? I haven't checked for air leaks yet but if that isn't it, I'm at a loss.

 

[jim_in_day]

Re: 1976 Johnson 70hp timing/high idle issue

jadoty, I know how frustrating this process is, I rebuilt my carbs 4 times in 2 weeks trying to solve the problem. I finally got it to run by playing the link and sync and timing game. Like I said, at TDC on the 76 70hp the RPMS on mine are 2000~2500 (I don't remember exactly where, but in that range). I then back the timing off to slow it down. If yours isn't wanting to stay running you may have the same problem I found, both my top and bottom seals were shot. Of course while I was in there I found a problem with my top piston, but I still had compression, it just didn't run right. Keep plugging, you will eventually find it. I am sure that I found my ghost, It just cost me a complete rebuild to fix it. I would be very interested is hearing how your problem gets resolved, so be sure to post it here

 

[Theoutdoorsman]

Re: 1976 Johnson 70hp timing/high idle issue

jadoty......... I recently had a problem with my evinrude 140, which was similar to your problem, after my rebuild. I found that I had two coils switched on the starboard side. The only difference in your description of your problem and mine was that your rpms are a little higher. I switched the two coils around and all is well now. No more coughing and the outboard idles great. You might consider double checking yours. Could it be that they got switched after replacing that head gasket? Good luck................... ALAN

 

[jadoty]

Re: 1976 Johnson 70hp timing/high idle issue

I'm glad there is someone with the same motor paying attention, so I will let you know if I come up with a solution. I assume the top/bottom seals fall into the air leak category by allowing air into the crankcase. I'm still a little confused on that in general though. Am I off base or doesn't an air leak result in running lean? Because in my case the plugs don't show any evidence of running lean. The coils, BTW couldn't have been switched because they don't come all the way off when the head comes off, they just unhook. Other than the timing itself, though, I haven't really done any real testing on the ignition.

 

[jim_in_day]

Re: 1976 Johnson 70hp timing/high idle issue

jadoty, test all your ignition components, not only making sure that you have the proverbial 7/16" spark across the gap, but pack output test, stator test and trigger test. I ended up replacing every electrical component in my motor (they all failed within a short time of each other) and still had the problem. I also ended up replacing my flywheel because we suspected a weak magnet when the motor warmed up was causing one of my problems. While it did help, its something I don't recommend as a new flywheel is $820 (I found a used one off a dead late model 3 cyl) keep after it, these engines run really sweet when they are finally dialed in.

Also, make sure that your wires from the pack go to the correct coils, since you got the boat with the idle set high, it may be that the PO switched one of the wires while replacing something.

 

[jadoty]

Re: 1976 Johnson 70hp timing/high idle issue

Had the boat on the lake Monday, and it is idling fine in neutral (although still high) but can't get any power in gear, so I assume that weighs in favor of an air leak in the fuel lines somewhere. I've already replaced the pump, some of the lines within the housing, and the quick connectors on each end. That leaves lines between the carbs, the pulse line or maybe the primer bulb or fuel tank pickup. Would an air leak in the crankcase such as top/bottom seals result in such a lack of power also or should I just be looking at the fuel flow? I'm getting no power at all in gear - got it up to 3500 rpms max.

 

[jadoty]

Re: 1976 Johnson 70hp timing/high idle issue

Idle level is down, maybe not where it should be yet, but found that despite all the link and syncs, the throttle plates were not all the way closed, so I backed the throttle cam even farther away from the roller, and am down to about 1200 rpms in gear.

Still have fuel delivery issue though, dies above about half throttle, and will die after awhile at idle. I can keep it going at low rpms by squeezing the primer bulb, so I know it's not getting fuel. Neither of the two brand new quick connectors I replaced seem to fit right, they wiggle, especially the tank end, which has a gap of about 1/32 inch where you can see the check pins on the pickup not being pushed all the way in. Is this likely the problem, and is there any reason why I can't bag the OMC tank and $120 pickup and go with a generic plastic tank?

 

[DJ]

Re: 1976 Johnson 70hp timing/high idle issue

Also check the barrel end on your throttle cable. I had one coming loose once and it did exactly as you described. Because of the slack, the timing plate wouldn't return to the rest or idle stop.