1990 Force 120 not firing??PICS ADDED

[MJS]

I went to the lake and took off. After about a half mile the engine bogged down and the tach went from 5000 to 3500. I went back to the marina and checked the plugs. The second plug was very fouled. I changed all the plugs and headed back out. The second cylinder was still not firing after new plugs.
My next step is to check the coils.
Could someone please help me figure out why there is no spark and how to track down the culprit?

I went out and started the engine on muffs and pulled the plug wire on the #2 and tried to see if it made a difference. It didnt change it at all. I put it on and removed it several times while the engine was running and couldnt tell a difference in the idol and saw no spark. I switched the coils from the #1 & #2 and started it again. I pulled the plug from the #2 and got a big surprise. I couldnt tell you if the idol changed. I was dancing all over the place trying to let go of that thing. There were blue lightning bolts 3'' long going to the block and my hand. I then tried it with the #1 and I was not shocked and no real change in the idol. Only when I would touch the wire back to the plug it would rev up for a half second then resume the rough idol. It seems the weak spark went to the #1 when I switched the coils.

 

[MJS]

Re: 1990 Force 120 not firing??

Re: 1990 Force 120 not firing??

deleted

 

[MJS]

Re: 1990 Force 120 not firing??

Re: 1990 Force 120 not firing??

deleted

 

[Jiggz]

Re: 1990 Force 120 not firing??

Re: 1990 Force 120 not firing??

Unfortunately, it's hard to follow your posts because of non-standard terminology. I think it will help if you can take pics and then post them while explaining what you did and what you found out. If you haven't done yet, you will need to check compressions on all 4 cylinders just to get that important test out of the way.

 

[MJS]

Re: 1990 Force 120 not firing??

Re: 1990 Force 120 not firing??

Unfortunately, it's hard to follow your posts because of non-standard terminology. I think it will help if you can take pics and then post them while explaining what you did and what you found out. If you haven't done yet, you will need to check compressions on all 4 cylinders just to get that important test out of the way.

Ill try to get a compression tester. I edited the original posts. Sorry. I can rebuild a car\truck engine with my eyes closed but Im trying to learn the layout and terms for the boats. Im new to these.

 

[Jiggz]

Re: 1990 Force 120 not firing??

Re: 1990 Force 120 not firing??

No apologies required. One time or another we all started in the same manner. The only reason I mentioned it so we can start communicating a little better and with pics if required. With digital cameras now almost the standard we should use them more to our advantages. Post your compression tests as soon as you get them and might as well include pics of the CD modules, ignition coils or plug wires you disconnected and switched. While you are at the auto store you might as well pick a spark plug tester the one where you can see the spark going through. It will help you now and in the future. It only costs around $5.

 

[MJS]

Re: 1990 Force 120 not firing??

Re: 1990 Force 120 not firing??

Ok, I have gotten a compression tester and spark tester. Spark looks good, nice and hot and jumps better than a 1/4 inch gap. Compression from top to bottom is 140, 25, 150, 150. Next question is it rings or gasket? Any way to tell?

 

[MJS]

Re: 1990 Force 120 not firing??

Re: 1990 Force 120 not firing??

I guess I should start by looking at the head gasket??
I remember reading something about putting oil in the cylinder to see if compression comes back. I know that won't last but a minute but does that indicate that it would be a ring if it did bump up the pressure?

 

[pnwboat]

Re: 1990 Force 120 not firing??

Re: 1990 Force 120 not firing??

I would start with the head gasket and hope that's all that's wrong. Head gasket is pretty easy to do. If it is the ring(s), with only 25 LBS of compression, the ring would probably be broken and possible piston/cylinder damage. Either way, you need to take the head off to check it out.

 

[MJS]

Re: 1990 Force 120 not firing??

Re: 1990 Force 120 not firing??

Can this head be saved? I dont think there is too much damage except for in the back near the port in the cylinder. Probably too much for honing, but how about boreing? But I dont know, maybe a hone would be fine. Ideas please. I know I would need a new piston and rings all the way around and a couple gaskets. Anything else?

 

[pnwboat]

Re: 1990 Force 120 not firing??

Re: 1990 Force 120 not firing??

To be 100% sure you should take it to a machine shop that does outboards and have them measure it. They'll tell you if it needs to be bored and if so, what over size piston you need. Or you could just try honing the cylinder and replace the piston and rings with the same size. Not the best route because if the cylinder is out of specs, the motor won't last as long as if you do it right. Another option is to get a used power head with good compression and put it on. This is probably the quickest easiest route. Not necessarily the cheapest though.

 

[MJS]

Re: 1990 Force 120 not firing??

Re: 1990 Force 120 not firing??

Can one cylinder be bored, or do they all have to be done?

 

[pnwboat]

Re: 1990 Force 120 not firing??

Re: 1990 Force 120 not firing??

Yes, boring just one cylinder is very common on outboards.