Replaced CDI,now what?

[5150abf]

1981 Evinrude 50
Won't run past 1800, replaced CDI with no effect,could it be the coils?
Absolutely not a fuel problem,starts and idles as normal but won't accelerate beyond 1800 rpm, even stumped the guru at work,.
Could weak coils cause it to not run at higher rpm?
Thanks for any help

 

[Silvertip]

Re: Replaced CDI,now what?

Let's start with some basics. Why did you replace the CDI unit?. You said it's definitely not a fuel problem! How did you determine that? Just because it idles does not mean its not a fuel problem. You also said it idles normal. An engine running on half it's cylinders will appear to idle normal. You need to verify spark will jump a gap of 1/2 inch on all cylinders. You need to do a compression check. You need to do a link & sync and verify that the throttle plates are opening fully. Have you tried pushing in on the key and squeezing the primer bulb when you have reached that 1800 RPM threshold. If the engine takes off momentarily you indeed have a fuel issue. If that doesn't help you probably have a linkage or spark problem (throttle opening or spark advance).

 

[5150abf]

Re: Replaced CDI,now what?

I have been trying to figure this out for awhile so I have already cleaned the carbs, the linkage is properly adjusted and there are no restrictions in the supply and the fuel pump is working, you can feel it pumping when you hold the bulb.
Yes I tried pumping the ball and it had no effect
I even looked at WOT with the carb cover off and you can't see the back of the carbs because of the gas fog so the high speed jets are flowing plenty of gas.( used a spot light down the throat).
I jumped a spark 3/4" from both cylinders.
compresion on both cylinders is 140,engine cold and it has new plugs and the timing is correctly set(2BTDC at idle 22-23 BTDC at full advance) and advances with the throttle,confirmed with a timing light and the butterflies are flat open.
For whatever reason it will come just off idle and that is it,runs steady, no surging or misfire and the choke will kill the engine if you hold it on.
It just won't acelerate beyond 1800 rpm.
Coils just seemed the next logical step.
I am going to pull the flywheel in the morning to check for any broken wires or something obviously wrong.
I am mystified, I have the money and they are 26 years old so they could probly use replacing anyhow.
If you can figure something out from what I have told please let me know, Thank you

 

[Walker]

Re: Replaced CDI,now what?

You've got compression, timing is correct and you have good strong spark. Next test is for spark when it is under load. If that checks then I suspect your carbs aren't as clean as you think, or if you removed the jets to clean them you put them back in in the wrong places.

 

[AntsGrady]

Re: Replaced CDI,now what?

I have a similar issue on my 84 35hp johnson. New plugs, new coils, new power pack, compression is good.....and idles super strong and high. However when I put in gear and go about 2000rpm's it starts to buck and the more gas I give it....it just shuts off rather abruptly. No clue where to go from here. Took the fuel filter/pump apart....looks good.....bulb seems ok.......probably gonna have to call a mechanic. This post seems very similar to my issue so I thought I'd chime in!!!

 

[5150abf]

Re: Replaced CDI,now what?

Mine doesn't stall, the exhaust tone just gets flatter.
I have run this by the 2 mechanics at work(40 years marine experience between them) and they are baffled by it.
Just tried to pull my fly wheel, broke 2 grade 8 bolts and it didn't budge,figured the good Lord was trying to tell me that wasn't where the problem is so I quit before I really broke something.
I was about to throw some heat on it but didn't want to melt anything,would that hurt anyhting to get the flywheel hot so it will come off?
Soaked the darn thing with WD 40 for a week and it still wouldn't budge using a 1/2"impact.
My thinking there was it is such a strange problem,everything works but doesn't, maybe one of the wires under the flywheel was broken and it seperated as the timing advanced, I'm up for anything at this point.
Gonna go order coils and plug wires now, like I said, they are 26 years old and it certainly can't hurt and the boat isn't going anywhere.

 

[Lubosleftboot]

Re: Replaced CDI,now what?

Sounds like an advance ignition timing problem to me.Just a thought for you to check out as if the ignition timing is out at above 1800rpm (i.e not advancing in time with the engine revolution) then the motor will run rough.

 

[5150abf]

Re: Replaced CDI,now what?

I have run it with the hood off and the timing arm advances to the stop like it should and I checked the timing at the stop and it is where it should be.
There is a group of wires that go under the flywheel and they move when the throttle advances and I was wanting to see if one of those was broken
That is why I wanted to pull the fly wheel but that didn't go well.
Will it hurt to put some heat on the fly wheel to get it off, I'm not talking cherry red but just heat it up to try and loosen it up.

 

[iwombat]

Re: Replaced CDI,now what?

You don't want to do that. Your magnets are held on with glue. If it's stuck, just place a solid whack with a hammer on the center bolt of your puller.

 

[5150abf]

Re: Replaced CDI,now what?

That is kinda what I thought,that's why I came here first.
My manual specifically says not to whack the center bolt but I may try that.
I am gonna go get a test tank and the coils off of a friends motor and try them before I buy new,we'll let you know how that goes.
Thanks

 

[5150abf]

Re: Replaced CDI,now what?

Got his tank but his motor is a 71-77 so the coils won't work.
At least I can mess with it running now and not have to drag it to the launch every time I try something.

 

[5150abf]

Re: Replaced CDI,now what?

Okay ran it in the tank,the rectifier is fried,tach won't work and it is putting out less than 1 volt to the battery cables with them disconnected from the battery.
Tach hasn't worked for a while, thought it was a wiring thing,hate wiring so I just let it go and I periodicly charge the start battery so I didn't catch that it wasn't charging.
With it running I pulled the top plug wire and it slowed the engine alittle, pulled the bottom one and it stalled almost imediately,same result with throttle so I will go ahead and order coils and a rectifier.
Plugs are new and compression is equal in both cylinders(140 cold) so it sounds to me like a weak coil.

 

[iwombat]

Re: Replaced CDI,now what?

Swap the coils and see if the symptoms change cylinders.