1974 9.9 one cylinder frustrations

[ironworker]

i have a 74 evinrude 9.9 that insists on running on the number 1 cylinder only. quick rundown... good compression(105 in the number1, 110 in the number 2), fuel pump rebuild, new gas, carb cleaned inspected, new plugs, points filed and cleaned regapped. i felt like it was electrical so i started switching the electrical components to try and isolate the weak link. Coils, condensers, points, chased all the wiring for pin holes. number one runs on all of them, number 2 wont. number two cylinder has spark, (i have a compression spark tester gapped at 1/4 inch and the spark looks the same as 1) is getting fuel mix in the cylinder and is forcing unburned fuel out the exhaust. Starting to feel like a valve issue but i dont know enough... any insight would be greatly appriciated... by the way i am new to this site and already i have learned a lot. thank you to everyone involved

 

[JB]

Re: 1974 9.9 one cylinder frustrations

You have wasted a lot of time and money fixing stuff that ain't broke, ironworker.That is the most used, most expensive and least effective troubleshooting method known to man.

With the exception of the points, condenser and coil for #2 everything you changed or overhauled is used by both cylinders. If any of them were bad it would not run at all.

Consider what is used by the dead cylinder only. Everything that serves both cylinders is working.

Having verified that the dead cylinder has spark and compression I would look to the scavenging. . . pumping action of the piston.

Are the reeds for #2 seating and not broken/chipped?

Are the gaskets for the intake manifold and bypass cover sound, not leaking?

Let us know what you find, and good luck.

 

[ironworker]

Re: 1974 9.9 one cylinder frustrations

sorry about the double post jb, luckily i didnt buy all of those parts, i just used some of the ones on the motor following the notion that if they worked on one they should work on two. the gaskets look okay but not sure. is it possible to get to the reed valves without removing the powerhead? what is the best method to inspect the reed valves and check the gaskets? thanks for your patients

 

[oldrudedude]

Re: 1974 9.9 one cylinder frustrations

By strobe testing I mean timing with a timing light. I believe your motor has two sets of points. My thought was that if #2 cylinder is not timed to fire at the proper time it is not going to give any power regardless of how strong the spark is.

If spark is good, timing on both cylinders is correct, and compression is good, better look to a fuel issue. If you rebuilt the fuel pump, that eliminates the leaking fuel pump diaphram issue mensioned by Rick on the other thread.

Don't get discouraged. You are new to outboards. Look how much you have learned already. Challenge is good!

 

[tashasdaddy]

Re: 1974 9.9 one cylinder frustrations

read this >>> http://forums.iboats.com/showthread.php?t=299680

 

[kbait]

Re: 1974 9.9 one cylinder frustrations

Check for lateral play in the mag plate. If it can move, it will change the point gap.

 

[jay mendoza]

Re: 1974 9.9 one cylinder frustrations

To check reed valves, remove both spark plugs, plug them back into the wires and ground the plugs. Next, pull the engine through slowly while listening and feeling for equal resistance(crankcase compression) and breathing( the reeds will wheeze as the piston rises). You should also hear each cylinder make a "thooop" sound as it's piston reaches the bottom of it's stroke, this is the sound of the compressed crankcase venting into the cylinder as the piston uncovers the transfer ports. If you don't hear this, suspect a crankcase leak (lower seal on crankshaft) or a bad reed valve.

 

[kbait]

Re: 1974 9.9 one cylinder frustrations

jay.. you are like a skilled surgeon! Great description!

 

[Chinewalker]

Re: 1974 9.9 one cylinder frustrations

Also, those maker point ignition systems can be fussy about having the points set at exactly 180-degrees apart. A sloppy mag plate or mis-gapped points can lead to misfires...

 

[Mandrake35]

Re: 1974 9.9 one cylinder frustrations

Just a thought....if your carb float is out of adjustment, it could allow fuel to flood out the lower cylinder.

 

[steelespike]

Re: 1974 9.9 one cylinder frustrations

Water intrusion into the cylinder could cause it to not fire right.
Any evidence of water droplets? Rust on the plug after sitting a while?

 

[bktheking]

Re: 1974 9.9 one cylinder frustrations

Water intrusion would leave one of the plugs sparkly clean plus compression would be off for a leaking head gasket. This sounds like a timing problem with misadjusted points or KBAITS issue. Getting spark, getting gas, getting compression but not firing at the right time causing gas to be expelled before spark occurs. I'd say look at KBAITS post for mag peening (or ask him about it) and check your gap again, something is off.


In the reserch I've done-

Now correct me if i'm wrong, bad reed valves would not cause a motor to not fire, they usually spit gas out the carb if they are bad. They will idle great but have a hard time with WOT. Reed almost never go bad, I pulled a set from my 9.9 powerhead that was full of water, the reeds were rusted on the surface but otherwise totally usable.

If you think they are bad pull the intake and look, it's only a few bolts to remove.

 

[Elbo]

Re: 1974 9.9 one cylinder frustrations

Most reed valves are behind the carburater,They close the crank case to allow a vaccum in the crank case.Most 2 cycle engines use this to run the fuel pump as well as charge the cylinders with fuel and for exhaust. strokes don't have a valve per cylinder like 4's dn a lot of jet skis ,snowmobils they use a huge exaust pipe to hold back pressure so the fuel air charge can,t escape.

 

[OptsyEagle]

Re: 1974 9.9 one cylinder frustrations

What spark plugs are you using? Everytime I mention this everyone thinks I'm crazy but on my 1975 9.9Hp (same motor really) which specifies Champion UL81C plugs, I used to get an intermittant cylinder issue. The boat would bog down then surge and then bog down. I figured a cylinder was intermittantly failing.

I verified compression was good, spark was wonderful and fuel and carburetor were working fine. For some reason I decided to change the spark plugs to NGK B7HS (champion equilivalents) and presto my problem went away. Since this made no sense to me and bothered me over the next few days, I decided to put a brand new set of Champion UL81C plugs in and my motor's problem returned immediately.

Needless to say, I use NGK B7HS plugs in my motor and never had the problem again. I use Champion plugs in other OMC motors with no problem at all, but my 1975 9.9 Evinrude (same motor as 1974-1976 9.9 to 15 HP) just does not seem to like them. I gave up trying to explain it but a few others have noticed this phenomemum on their motors since then and are using the NGKs now as well.

 

[bktheking]

Re: 1974 9.9 one cylinder frustrations

Worth a try, I had a 75 , put champions in it and it ran like a champ, must be motor specific.