1980 85 HP Johnson - stalls when idling, runs great above 1500 RPM

smak90

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I just installed an old 1980 85 horse on my boat that had been sitting outside laying on its side for probably 10 years. I had bought it a while back for $300 with the intention of a future project or to part out. My regular engine blew a couple weeks ago so I decided to put the 1980 85 HP on my boat.

So far I've done the following to the engine: removed probably 20 mud dauber nests from engine and carb, installed new starter (was missing), 2 new power packs (1 was bad), new coils (from my blown engine), new seals on lower unit, new impeller, rebuilt carbs (one was full of mud dauber nests), replaced all fuel lines with new ethanol resistant lines), new primer unit, verified great compression (125 psi on all 4 cylinders).

I ran her for the first time today. The engine ran perfect above 1500 RPMs. I took her to 5100 RPMs and it sounded tight, as good as a brand new engine. Perfect power through all RPM ranges. Temperature on the heads is 140 degrees after running it WOT.

Idling is another story though. If I run it hard it idles good for a minute or 2. The rest of the time it stumbles, it sounds good for 2 or 3 seconds and then dies abruptly. When starting it usually fires up fast and then may try to die 2 or 3 seconds later. Hitting the primer can help to keep it going.

I'm leaning toward a carburetor problem, especially since there had been a mud dauber nest in one when I rebuilt it. There were also fire ants in there eating the mud dauber larvae from the nests. All jets were removed and cleaned before but I'm thinking maybe one of the tiny passage ways has an obstruction somewhere. Does this sound like I'm looking in the right direction?

Other things I'm wondering about:
Could bad stator cause something like this? I don't see drip marks or anything coming down from under the flywheel.
Could bad rectifier cause this? I'm pretty sure its bad since I don't see any charging happening on the amp gauge.
Could something in the intake manifold or bad reeds cause something like this (it looked clean in there when I pulled the carbs so I didn't think there was any reason to remove the manifold. I'm a little concerned due to the earlier mentioned mud daubers and fire ants though).
If there was a bad wire or bad ground, would the engine be running so good at high speed?
Could cloged check valves on the intake manifold cause a symptom like this? I broke one and replaced it, the original seemed really dirty. I know I should pull the rest of them and attempt to clean them but they were made of plastic back then and I'm concerned with breaking them. Could blockages cause bad idle?
 

bonz_d

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I have to agree with your 1st assesment that it's in the carbs low speed circuit that it isn't idling well.. Otherwise it sounds as if you've done everything right. If there is a tach onboard what is the rpm when Idling?
 

jerryjerry05

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Low speed air/fuel possibly a bit of dirt still in the system??
Had the same problem on a 125 I cleaned the carb 4 times.
The first 3 did nothing.
The 4th did the trick.
Still running great.
The jets are both in the carbs bowl clean again.Also maybe the float needs adjusting
 
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smak90

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I pulled the carbs last night and went through them again. I found 2 different passageways that had a small glob of dirt. One seems completely blocked while the other appears to be restricted but not blocked. I'm anxious to get it back together this evening and run her on the muffs. I'm pretty sure that has got to be the problem. When I was on the water Saturday the RPMs at idle seemed to stay around 1000 so I think the idle speed is ok. I'll let you know how it goes. Thanks for the input.
 

bonz_d

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Good job! now do you know when the last time the fuel lines were replaced? If it's been awhile I'd do it now or you may suffer the same problem.
 

emdsapmgr

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Agree with bonz. If that engine still has any original fuel hoses-that could be part of the problem. They are not ethanol compliant and tend to disintegrate with age. Parts of the hose could break loose (black bits) and migrate downstream into the jets.
 

smak90

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Thanks for the advice everyone. I replaced all of the internal fuel lines and primer lines hoses with modern ethanol compliant hoses about 3 weeks ago before ever attempting to crank this engine. I made long runs with large bends in the places where I replaced OMC custom hoses so I think I'm good with the fuel delivery. I re-installed the carbs again last night and ran it on the muffs. It idles better before but it still had a a slight stumble. I had to keep priming it when it was cold to keep her running but once she warmed up it kept running and didn't die although there was still a stumble. I'll take her out again this coming weekend and see how she does at the lake when there's some back pressure. This project continues to move in the right direction so I'm happy with the progress.

I really got lucky with this engine since it had all the appearances of one ready for the scrapyard. Running it at speed and WOT it runs and sounds like a brand new motor. There are no little rattles or noises that I've always heard on past engines I've owned that were much much newer. This thing is 34 years old and it is the best sounding engine I have ever owned. It's been very rewarding to bring this 34 year engine back from the dead.
 

bonz_d

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Good to hear you are making progress, have you a manual or the written procedure to do a link n' sync?
 

emdsapmgr

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It's normal to have to keep choking the engine periodically for the first minute after it starts-till it warms up.
 

smak90

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I've got the shop manual for my old 1994 88 SPL. Is there enough difference between the 1980 and the 1994 to make it worth it to get the 1980 shop manual. So far working on the 2 engines everything is very similar except maybe the ignition. What do you think Bonz?
 

bonz_d

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I will admit, I'm not a V4 guy so I really don't kow how much difference there is but I can say this. I have a 1975 50hp and a 1987 50hp Johnson which I have manuals for and a 1983 60hp that I don't have one for. There is enough difference between the 2 manuals that it may well be worth it. Much more info in the 1987 manual than in the 1975 one.
 

smak90

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Here's an update on what I've done since my original posts on this.
- Tore the carbs down a third time and went through them again and they are spotless.
- I went ahead and rebuilt the fuel pump. When I removed it there was a mud dauber nest on the back covering the little air hole on the back.
- I found voltage leaking to the kill wire (blk wire with yellow stripe). It was leaking through the wire harness on the engine so I ran a new wire outside the harness to correct the problem.
- Tested all the ohm and DVA voltages for the trigger and stator. I found the following:
- all ohms and voltages within spec although one stator to power pack lead was at the bare minimum
- Found positive voltage when testing single stator leads to ground. The 4 leads all had voltage ranging from 20 volts to 200 volts.. I was using the DVA on my multimeter to get the measurements. According to my 1994 Johnson Manual these should all be zero. I'm still waiting for my 1980 service manual.

- After each thing I've done the engine idle performance has improved but there is still a miss at idle.

I've got 2 questions:
- Am I correct to assume stator must be replaced if voltage is leaking to ground? I can't see any broken wires but I haven't pulled the flywheel yet.
- Is there any point in buying used a stator off ebay or are most of them going to have problems being over 30 years old. I suspect there are better electronics in the new ones manufactured today but I have a hard time shelling out $250 if I don't have to.

Thanks to everyone who has already responded. I think I'm almost to the finish line.
 

emdsapmgr

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This website has some excellent ignition troubleshooting info: cdielectronics.com Their site has exact specs for condemning cranking ouput voltages for the stator and timer base for your engine. You need to see at least 150 volts from the stator and at least 0.6 volts from the timer base. As measured with your peak reading voltmeter while cranking. Anything less and they should be replaced. There are a number of changes from 1980 to 1994. The carbs are different regarding the idle plate on the 94's. The fuel primer systems are similar, but don't feed the carbs like the 94. The 80 uses two power packs, the 94 has one. Since you have a factory service manual for the 94 88, it should cover the simple fuel pump and the rectifier-same on your 80 model. The power trim systems are different. The 80 uses a 3-wire motor and a separate trim box which mounts under the splashwell, the 94 uses a two wire system-these systems have few common parts between them. The shift mechanism under the bottom carb is dissimilar. Most of the other mechanicals are similar.
 

bonz_d

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Sounds as though you are doing a very throrough job and headed in the right direction.
 
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