Dirty Cyls 73 20 hp johnson

[chiefcatchemall]

Well the other day I was trying to fire up my motor. I would get it to run for about 15 seconds then it would die. It would run rough however. I did get it to run for about a minute and a half one time. But again, it was running quite rough. After each time it quit I pulled the plugs to look at them. They were wet with gas, but they were BLACK! So I pulled the plugs and shined a flashlight in there and noticed that noticed quite a bit of black build up. Is there anything that will take care of this? Can I hit it with a good squirt of sea foam and let it sit for a while?

 

[CatfishMN]

Re: Dirty Cyls 73 20 hp johnson

Sounds like carbon build up to me. Look in the Top Secret Files about how to do a decarb.

It also sounds like you are having unburnt fuel/oil in the cylinders. Have you checked your spark on both leads?

 

[chiefcatchemall]

Re: Dirty Cyls 73 20 hp johnson

Thanks for the speedy reply. Yes it is deff carbon build up. Yes, I replaced almost all electrical in the motor. New ignition coil, new points & condensers, etc...Great spark that jumps a 1/4'' on a spark tester. This was a motor that I bought over the winter that hasnt run in about 4 years. So im sure he had some electrical problems with it before I purchased it...

 

[steelespike]

Re: Dirty Cyls 73 20 hp johnson

Won't hurt to do the decarb but carbon is not your problem.Is this motor new to you? Or first time fired up in a long time?
If it has sat a long time the fuel system will likely need to be gone through from tank to carb.
If the coils havewn't been replaced they are probably in need of replacement. pull the flywheel and have a look.
The points probably need cleaning and adjustment anyway.

 

[chiefcatchemall]

Re: Dirty Cyls 73 20 hp johnson

New gas, mixed 50:1. New ignition coil, new points gapped to .020, new condensers. Rebuilt carb, used compressed air in jets and all passages. Rebuilt water pump, changed lower unit oil. Thats everything I have done to it...This motor is new to me. Bought it off a guy just before winter. 300 dollars. It was a steal I thought. Motor is in great shape, very clean. Compression is 105&108...

 

[itsaboattime]

Re: Dirty Cyls 73 20 hp johnson

May sound silly, but are the plugs and wires new as well?
I understand the spark makes the jump on the tester, but if the plug has issues your spark strength won't amount to a hill of beans.

 

[chiefcatchemall]

Re: Dirty Cyls 73 20 hp johnson

May sound silly, but are the plugs and wires new as well?
I understand the spark makes the jump on the tester, but if the plug has issues your spark strength won't amount to a hill of beans.

Yup, they sure are new!!

 

[AlTn]

Re: Dirty Cyls 73 20 hp johnson

chief..go to the next page over and read a thread ,'Where should I start? Carb?", OP scrit9mm...you have the same ignition system...try those plugs if they aren't already what you have..post back

 

[chiefcatchemall]

Re: Dirty Cyls 73 20 hp johnson

Well right now I have champion j4c plugs in it. Which another poster said would work fine on that thread you just had me read...If I can find the UJ4J champion plugs that the guy used then I will get them and try it! Or like he did I will get them cross referenced and get the auto-lite plugs... I also didn't even think about the fuel tank situation...If I screw my cap on tight and let it sit for a few mins then back off of it a quarter turn it releases some pressure. So from what I read, my understanding is that I should keep the cap backed off a quarter turn so the tank doesnt build pressure on its own?



All of this is great information, that I will be trying here in the next few days. But how does this change the fact that when I look in the cyls they have a lot of carbon build up in them. I still need to perform a decarb on the motor dont I?

 

[BonairII]

Re: Dirty Cyls 73 20 hp johnson

Periodic decarbing is def a good way to keep carbon to a minimum and your rings happy.

Doing a decarb is pretty darn easy, but you're going to have to get your motor running properly before you can do it. It involves running a mixture of premix and seafoam thru your running motor. You can decarb by simply spraying seafoam into the cylinders.

 

[chiefcatchemall]

Re: Dirty Cyls 73 20 hp johnson

Periodic decarbing is def a good way to keep carbon to a minimum and your rings happy.

Doing a decarb is pretty darn easy, but you're going to have to get your motor running properly before you can do it. It involves running a mixture of premix and seafoam thru your running motor. You can decarb by simply spraying seafoam into the cylinders.

Well what if that is my problem and why its not running right?...is this possible? When I had it running for a min and a half I pulled the plugs and they were BLACK. I am assuming that was the problem. But then again thats an assumption...If I cant keep the motor running long enough to decarb it, do I need to tear it down?

 

[BonairII]

Re: Dirty Cyls 73 20 hp johnson

I wonder if it's somehow possible that you're losing spark(or spark is weakening)as soon as the motor starts warming up. Do you have a timing light?

Are all connections to coil etc etc tight/clean?

 

[chiefcatchemall]

Re: Dirty Cyls 73 20 hp johnson

no timing light. connections are tight and clean

 

[CatfishMN]

Re: Dirty Cyls 73 20 hp johnson

I was going to say possibly a bad condenser because I have read that older ones may fail when they reach operating temp, but he says he replaced them...

 

[bbstacker1]

Re: Dirty Cyls 73 20 hp johnson

If I read right earlier you said the carb was rebuilt, what do you have the low speed setting at? Should be around 1.5 turns out to start then adjust from there. There may still be some junk in the carb, will it run long enough to rev it up a little, off idle, if so does it run better, if so I would be thinking, adjustment to low speed or dirt/junk in circuit. You said new plugs, maybe one is bad try a new set and make sure of your point settings and that they are clean. Do the cheap easy stuff first.

 

[scrit9mm]

Re: Dirty Cyls 73 20 hp johnson

When it ran for that min or so did it sound like it was running at a high rpm or barely running. How far is your low speed needle unscrewed?

 

[BonairII]

Re: Dirty Cyls 73 20 hp johnson

How far is your low speed needle unscrewed?

I'm wondering the same thing. Maybe running so rich it's smothering the plugs.

Chief,
Did you inspect the needle for wear or possibly the tip has been broken off and still in the carb?

 

[chiefcatchemall]

Re: Dirty Cyls 73 20 hp johnson

Deff no gunk in the carb...Needle looks really good to me...I am going to have to play with the low speed jet...So I screw it in all the way then turn it out a turn and a half to start?

 

[BonairII]

Re: Dirty Cyls 73 20 hp johnson

That's normally a good starting point.

 

[bbstacker1]

Re: Dirty Cyls 73 20 hp johnson

Chief, just remember when turning it in (seating it) to go easy, lightly seat it so as not to damage the tip.