120 Johnson stalling low idle

[timej]

I have a 93-94 Johnson v4 120 that idles good(stalls ocassionally), starts good, WOT good-but stalls at low rpm or hesitates to about 1500 RPM. Plugs are wet fouled- all are the same. Changed plugs, removed VRO ran tuner through the system. Haven't tried in the water since I disconnected VRO. I figured if I can get the plugs clean the problem would be solved. Plugs seem a bit cleaner after i removed VRO above but still show oil and gas. Also is it normal for fuel to leak out when engine is fully tilted back? Any help would be greatly appreciated [*]null

 

[Dhadley]

Re: 120 Johnson stalling low idle

Are the carbs clean? Has it always done this? What plugs? What fuel? What oil? Did it start doing this right after a carb job?<br /><br />Good luck!

 

[timej]

Re: 120 Johnson stalling low idle

Thanks for the speedy response. The fuel is standard 87 octane with OMC oil 50:1, didn't rebuild carb. This is my first year with this boat and it has always had the problem. Tried advancing timing with little success. Plugs are the QL?78? Though originally I had the ?77? plugs in with same result.<br /><br />Thanks

 

[Dhadley]

Re: 120 Johnson stalling low idle

Since you are starting with this boat and motor I would suggest a carb overhaul job just to make sure the basics are covered. <br /><br />Good choice on the fuel and oil. Either plug is OK also. When you say you adjusted timing, I think you mean idle timing not WOT timing. Right?<br /><br />Keep us informed and good luck!

 

[ed_j4]

Re: 120 Johnson stalling low idle

Do you have a carb on the engine? I have a 1990 Johnson 120hp V4 and it is EFI.

 

[Jonathan Moore]

Re: 120 Johnson stalling low idle

I may have same problem. What is a VRO tuner?<br />Cheers<br />JM

 

[timej]

Re: 120 Johnson stalling low idle

The motor actually has 4 carburetors. The VRO is the variable ratio oil mixing pump.The tuner is for removing carbon deposits-it gets injected into the schrader valve below the fuel pump-should have a red lever. Seems to work well but didn't solve my problem.<br /><br />Let me know if you guys find anything out.

 

[Dhadley]

Re: 120 Johnson stalling low idle

Hey ed_j4 -- You sure you have fuel injection on a 1990 120 Johnson? I'd love to hear more about it.<br /><br />Let me know. Thanks.

 

[ed_j4]

Re: 120 Johnson stalling low idle

I am not 100% on the carb, now that is brought into question. This is a new OB for me. With the cowling off, where I expect the carbs (typically in front of the cam) is a cover that looks like part of a throttle body fuel injection system, similar to '89 car with an 1800 I had, although I did not notice a throttle body. So I made a quick assumption. I'm going to look into it further when I go see the boat this weekend, and get back to you.<br /><br />As for the other question, the motor shouldn't leak much fuel in any position, and is particularly unsafe if it leaked a fair amount of fuel in the tilted position (that it is transported in I assume). This would create fumes under the cowling, which is not typically equipped with a blower and would lead to a dangerous situation.

 

[timej]

Re: 120 Johnson stalling low idle

Hey -I think I solved the leaking fuel problem defective gasket in cowling. Can anybody tell me anyhting about adjusting the timing. My motor is idling about 1600 RPMs with a hose connected and my timing light doesn't seem to work to well-is there something I am not doing right? How do I get my idle down? Also does anybody know the proper procedure for adjusting the air mixture(adjustment screws on the outside of the cowling)- I looked in Clymers and couldn't fine anything about it.<br />Thanks

 

[Dhadley]

Re: 120 Johnson stalling low idle

Don't worry about the high idle on the hose. It's not unusual for a looper. You have no backpressure on the flushette plus the motor may not come out of Quick Start because of the cold water. Or it may come out and go right back in. Anyway set the idle in the water. <br /><br />Now, if the motor won't idle down in the water it's a different problem. <br /><br />As for the needle valve adjustment, get the correct year and go to that service manual. Be careful to pay attention to the suffix in the model number. They used a couple of carbs in those years and the suffix will tell you which one you have.<br /><br />Good luck!

 

[timej]

Re: 120 Johnson stalling low idle

Found the idle air mixture specs in clymer- 2 turns out. I got the boat in the water and in forward gear it idles at ~575-600 RPM. The stalling problem is gone except now the motor runs rough (vibrates) upto 3000 RPMs then runs great at WOT-I noticed the rough operation disappears when the high speed timing advance? engages. I didn't have the problem before when I had the QL77? plugs in-changed to 78 champion plugs. Both plugs are spec'd by clymers with the 78 plug recommended for extended high speed operation.<br /> <br />Questions: Can I advance the idle timing to get to ~700-800 RPM at idle?. Are there any dangers in doing this? Can the different plugs cause the rough operation? What is the difference between the plugs? <br />Plugs are gapped at .030" as per spec.<br />What does preignition sound like? <br /><br />How do you fine tune the air mixture or should I just leave it at the 2 turns and forget about it? There is no instruction in clymers.<br /><br />Any help is much appreciated.