High idle on 35hp Johnson

Elund09

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77' 35hp Johnson, Model 35EL77H. Was on the Mississippi wide open, headed to the fishing hole. Everything was fine. Backed off when I got to the "No Wake" zone and soon after she started knocking a bit. So now at low speed it ran funny but headed back at high speed it was fine. On the next outing things got worse. Engine was shaking back an forth, idle would be normal then high and back and forth. Shut it down and it wouldn't restart.
At home I got it going again but now it is at a very high idle all the time. Put in a carb kit and checked all the linkage. All good there. Still runs on a high idle. The low speed adjustment has to be open quite a bit to slow it down, flooding it, in which it still runs poorly.
The spark plugs are fouled and fuel is visible in one of the cylinders.

Any thoughts anyone? Thanks.
Erik
 

Daviet

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Re: High idle on 35hp Johnson

You said that fuel was visable on one of the plugs, check spark and compression on both cylinders.
 

Elund09

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Re: High idle on 35hp Johnson

I have spark on both plugs. Do I need a compression tester? I placed my thumb over both holes one at a time and they seem to be equal in pressure. I also mixed up a gallon of new fuel, same high idle still.
If it were a compression problem, where would I go from there? What psi should it be?
 

yellowbelly

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Jul 11, 2008
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Re: High idle on 35hp Johnson

every motor will be different but you want both cylinders to be close..
 

Elund09

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Re: High idle on 35hp Johnson

Ok lets recap begining with the original symptoms in the order they occured/increased.
1. At low speed every now and then would, for lack of a better word, go "blah" for just a second then back to running fine. Now and then the "blah" would actually kill the engine. Just fire it up again and back running.

2. At low speed the engine would, on its own, run faster for a few seconds then back to where it was. Sometimes up and down multiple times.

3.Now it only idles at a high speed

4.Ran terrible at a low speed, shaking the engine quite a bit.

5.Ran good at high speed but now this too develops the same rough running as the low speed. Shut engine down and would not restart in the water.

6.A week later, when I found time, got it restarted using muffs. It now runs on a very high idle. Put in a carb kit and it still runs on a high idle.

7.Back in the water it starts, has a high idle. Put it in gear and she kills in seconds. Will not restart. Back at home she still won't start.
----------------------
-So I have put in a carb kit, was spotless in there.
-I have spark.
-Compression averages 105 psi on both cylinders with 4 psi difference between the two
-Fuel is on the spark plugs, visual/smell

Thanks for the help so far, any more thoughts? Thanks, Erik
 

Daviet

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Re: High idle on 35hp Johnson

Just a thought, do you have excessive fuel on both plugs or just the bottom one? Thinking maybe you have a blown fuel pump diaphram allowing fuel into one cylinder. Vacume leak could cause engine to rev up.
 

Elund09

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Re: High idle on 35hp Johnson

Theres accessive fuel on both of them but twice as much on the bottom one. Your response makes sense considering the problems keep getting worse to the point it will no longer start, thank you. I've kept saying to myself theres too much fuel, why. Would a blown fuel pump cause a vacume leak? Is the pump somewhere behind the filter?
 

Daviet

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Re: High idle on 35hp Johnson

Your fuel pump is vacume driven. It is pulsed by the cylinder going back and forth. The pump is mounted on the block, there is a gasket between the pump and the block. If the diaphram is leaking fuel, the piston going back and forth will suck fuel directly into the cylinder, bypassing the carb. Follow your fuel line from the connector on the engine, it will go to the pump, has a large silver screw holding the cap on. The pump then pumps fuel to the carb. Do you have a manual for your engine, The manual can answer lots of questions.
 

Elund09

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Re: High idle on 35hp Johnson

I don't have a manual, I should get one. Every penny counts these days being a Carpenter. I took the pump apart. The gasket under the cover (the one with the big screw) has a nice tear in the center. No sign of a tear in the diaphram, or what I think is the diaphram inside the pump. I'll check the gasket between the pump and block tomorrow. I'll go to the library and get a manual. I just need a fuel pump kit right, not a whole new pump? Learning on the fly here, kinda obvious I suppose.
Thanks for the help, Erik
 

Daviet

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Re: High idle on 35hp Johnson

Need model number to see if you can get just the pump kit. Get the manual and double check everything, I don't want to lead you down the wrong path, hard to figure out some of these problems without being able to touch, feel or hear the motor running.
 

Elund09

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Re: High idle on 35hp Johnson

Fuel pump is good. Getting good spark with even a 3/8ths gap. Went thru the carb again, lowered the fuel level in the bowl. Same high idle. I don't know why but I'm sure its running on one cylinder. Thanks for all the help. Guess ima have to take it to the shop.
 

bagnallt

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Jan 27, 2008
Messages
63
Re: High idle on 35hp Johnson

Hi there... I have a 30 hp jonny that i "play with" you might find that you have a good spark at test but still it may be that are getting a leak or an arc at idle hence firing not on every stroke..... At nigh time run the motor ad look to see if you can see arcing. Thats what i had. Took me 3 weeks.. 4 carb rebuilds one new fuel pump to find it. It was by accident i found it.. I woke in the night though I haddnt checked to see if the stator was melted.
I started the motor and it was like seeing lightning at idle.. it was all over the place.. pulgs out wet with fuel...... so i cheated at first put electric tape arround the leads tried it was lot better. replace the coils and leads and it ran great... It would run "ok" at fast speed but not at idle before i did this....
 

Elund09

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Re: High idle on 35hp Johnson

Thanks, I'll check it out tonight. After checking everything else the guys at Marine 61 said it would be either in the carb or not enough spark. When I checked for spark I held the plug by the wire, grounding it, while my wife cranked the engine. I got one hell of a shock! It never dawned on me that the shock would be from an arching wire. Sure makes sense now.
I'm still trying to figure out why this would cause the high idle. Engine compensating for itself. Or would one cylinder take off when the two aren't working/firing together?
 

Elund09

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Re: High idle on 35hp Johnson

I have installed new ignition coils and spark plugs. It is very tough to get started and if it does it runs fast and rough.
Something different now however. The lower cylinder plug is blackened but dry. The top cylinder plug is wet.
If I disconnect the top plug wire, I could get it to start on the bottom cylinder only. I could not get it to start on the top cylinder only.
I checked for spark again and have It on both plugs.
Went thru the carb again, soaked it for 24hrs, and carb cleaner was visible spraying over iner butterfly while hosing into idle tube.
Looked at the manual and am still stumped. Seems its running on the lower cylinder only. Am I wrong on this assumption, any thoughts?
Thanks again everyone.
 

Elund09

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Re: High idle on 35hp Johnson

Just wondering, could a CDI Power Pack be the cause any of my problems? Could it still deliver power to the ignition coils but be off in the timing? I believe this 77' 35hp runs off a magneto and not points.
Anyone know how to adjust timing on a magneto or is it the job of the CDI to do this?
I replaced the stator a couple years ago.
Haven't been able to get it to start the last few times I've tried. Cranking on is so hard heats up the possitive terminal on the battery.
Any help is greatly appreciated.
 

Elund09

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Re: High idle on 35hp Johnson

Well i decided to start taking everything apart, inspect and replace all the fuel lines. I found a leak in the fuel connector at the tank and replaced it. I removed the flywheel and much to my surprise the crankshaft key was sheered off. Metal shavings were everywhere and it was obvious the flywheel had been spinning around on the crankshaft.
I ordered a new key, will carefully grind out the piece left in the crankshaft tomorrow.
Does anyone know if the seal around the crankshaft can be replaced without splitting the block in 2? I think the metal shavings may have caused some dammage to the seal.
 

Elund09

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Aug 14, 2009
Messages
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Re: High idle on 35hp Johnson

Got the new crankshaft key and after install, she is purrin' like a kitten. This old '77 runs on a CD Ignition, and with the magnets on the flywheel not in the proper location in relation to the crankshaft/stator, threw it way off timing.
The best thing I did in this situation was to remove the flywheel. Tear it apart and inspect everything!
 

jonesg

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Feb 22, 2008
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Re: High idle on 35hp Johnson

Thanks for posting the resolution back, thats what makes this thing work.
 
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