94 Johnson 120 V4

[johnboyj]

I have a 94 stratos with a Johnson 120 V4. It idles great and jumps up on plane great, after about 30 seconds the motor dies back down to a skipping and spitting idle, it will try to get back on plane but doesn't have the power. We have replaced plugs, VRO pump, rebuilt carbs, replaced fuel lines, and fuel filter. Not for sure but the only thing left that could cause it is power pack or ignition coils. Wanted an enlightend opinion on what it could be.

 

[tashasdaddy]

Re: 94 Johnson 120 V4

well, you haven't check the spark when it is acting bad. take and induction timing light, and check the spark on each plug wire, when it acts bad. this will lead you to the ones that are missing.

 

[ezeke]

Re: 94 Johnson 120 V4

The 120 has a fairly sophisticated ignition system with QuikStart and S.L.O.W.

S.L.O.W. cuts the engine to 2500 RPM when the overheat switch connects. It should sound the horn alarm at the same time, though.

 

[tashasdaddy]

Re: 94 Johnson 120 V4

that's also a good possibility. downing into slow mode.

 

[johnboyj]

Re: 94 Johnson 120 V4

well we thought the same thing and no alarms go off, we didn't have the timing induction done though. See my brother thinks its the power pack, I think that one or two of the coils are going bad which will be causing the skipping. But Im definitley not a pro on outboard motors

 

[HighTrim]

Re: 94 Johnson 120 V4

I agree with Tash, determine if you are dropping a cylinder once it starts acting up. Using insulated "spark plug" pliers, pull one boot at a time, noting the RPM's. If there is no noticable difference, that cylinder is dead. You should notice a considerable difference in RPMs. The inductive timing light is the safer/easier route however.

You could also try heating the ignition components up with a hair dryer, then testing the spark with an inline adjustable gauge set to 7/16 of an inch.

 

[ezeke]

Re: 94 Johnson 120 V4

I would agree with HighTrim that it is safer to test with the inductive timing light.

The last time that I checked a looper by pulling wires I killed a perfectly good powerpack. I have never had that happen on any crossflow, and I still don't know why it happened, but be forewarned.

 

[johnboyj]

Re: 94 Johnson 120 V4

Thanks for the warning. Havent tried anything yet been nasty weather round here. I put it in the shop monday, they checked everything out and said nothing is wrong with it. They brought it out on the lake and it ran great, but it was a warm day so i was wondering if it might have an intermittent program, run great on a warm day and die out on cold days. Its gonna be a little cooler on sunday so we are gonna try it again and see if that may be the case. If so then I will be positive that it is the power pack.

 

[johnboyj]

Re: 94 Johnson 120 V4

Ok guys we tried it out today the boat is still running bad. We started out it ran great, (temp was about 45 fh) we went about 3 miles wot without any probs, we stopped and fished for about 20-30 mins and decieded it wasn't a good place. So we got back on plane wot for about 5 miles stopped and fished for an hour. No probs. We started to go south and about 2 miles into it, it started its problems but not as bad as before it only came down to just right above plane and kept it that was for a half a mile, then completely stopped to an idle. No ideas why it would do that. I had someone tell me that the power pack may get too warm and start shutting cylinders down but any way, we were babying it back in and the alarm went off, solid long beep. Which made us think it may have been an temperature sensor. We shut the motor off for about 5 min. , and trolled for awhile. I started the motor back up and no alarm but was still skipping. We were probably about 1/2 mi. from the dock so I just let it idle back in. Then, about 1/4 mi. from the dock, it was like someone flipped a switch, all of the cylinders were firing and running smooth. With it doing that it really has me pulling toward power pack idea. Or would the power pack make it shut the cylinders off and on like that. I know its not the coils because, it was all simultanious. Just like you were pulling the plug wires on two cylinders at the same time. Any advice is greatly appreciated, I may not have too much hair left.