Help !! Johnson 50 '84

[maggun]

We have a Johnson 50 hp 1984 mod.<br /><br />Mod. nr. J50BELCRM<br /><br />We have problems with running this engine at high rpm's, if I try to give throttle, it just dies suddenly. This happens, even though we have let it run for at least 10 min., letting it get warm.<br /><br />I have tried to overcom this issue by servicing the carburators, disassembling them, and with that replacing the inlet valves on both carbs. I followed the steps from the repair manual when servicing the carbs. cleaned them, and removed any potential debris/dirt in any of the orifices. To my understanding there are no tuning screws, so all was just fastened tightly as usual. We have also replaced and fixed any potential problems with the fuel lines, also, I have tried the fuel pump by running the engine with the starter, and there seems to be a good flow of fuel from the pump, also cleaned the filter with that.<br /><br />I am dead in the water here, literally, the engines runs presumably ok at low rpm, but as said, it dies if I try to use it in normal operating rpm's. I am really frustrated at this point, I have no idea on what can be wrong, do you ?<br /><br />Any hints is greatly appreciated.<br /><br />Thanks in advance.. <br />-Magnus

 

[ob]

Re: Help !! Johnson 50 '84

Perform link and synch procedure as per manual to insure that the carb linkage is in time with the ignition advance.<br /><br />Also when attempting to throttle up you could try repeatedly bumping the primer swutch and see if engine picks up.If so,it would indicate that there is a fuel delivery problem through carbs.

 

[maggun]

Re: Help !! Johnson 50 '84

Linking and synching is now done, but still it dies when giving throttle.<br /><br />I was told by the local johnson dealer that you will not experience problems to the degree of the engine dying if carb/ignition is out of synch. But rather performance problems.<br /><br />I have done some further testing today. And have additional information that I hope will give a clue as to what might be wrong.<br /><br />The engine starts rather easy, one attempt with choke is enough, but it stops shortly after. Start again, and stops shortly.. it takes some attempts before it runs ok. I also took a more thorough inspection on what goes on when I give throttle alone with the linkage connecting the two carburators. And what I noticed is that it seems to missfire/backfire frequently. This happens only when I apply throttle, in idle it runs seemingly ok. In forward there is a limit on how much throttle it will accept before it dies, on this threshold it acts kinda jerky. If i try to add more throttle slooowly, it dies. While in this threshold I tried using the squeze bulb on the fuel line from the fuel tank, to see if the fuel pump was bad, but no help. I also tried running the starter with the fuel line disconnected to check the stream, and sure enough there is a pulsating stream of fuel from the fuel pump.<br /><br />Any ideas ?

 

[The Marine Doctor]

Re: Help !! Johnson 50 '84

When you check your spark plugs...are any of them wet?<br /><br />TMD

 

[maggun]

Re: Help !! Johnson 50 '84

I wen't down and took a look at them right now, the engine was last tested yesterday. The top spark plug looked blakish on the insulator especially and on the center electrode, the shell looked moist and with some black debris, the lower plug was similar but looked to have more black debris on the shell than the top plug and this too was moist. Not soaking wet, but certainly not dry. And as said, it has been many hours since it was operating. The reason I haven't tested and then checked the plug as you said, is that the boat is now out of the water. I hope to do some more testing as soon as help arrives today wich will let me move preferably the engine to a test tank.<br /><br />This TYPE IV carburator wich they are called, are not adjustable to my knowledge, with fixed orifices, wich will not let you adjust the mixture on this engine ?

 

[maggun]

Re: Help !! Johnson 50 '84

Hey<br /><br />It looks like the top plug is more wet than the lower plug. Also after further testing today, I have noticed that if I remove the top spark plug lead, the engine runs pretty ok even though it is running on the lower cylinder alone. If I reconnect the top and disconnect the lower, so that the engine is only operating with the top cylinder alone, it seems to stumble more, just barely running in contrast to running the bottom cylinder alone. Another thing, when the lower is disconnected, sparks fly from the lead, also saw sparks directly from the coil firing to the powerhouse. This does not happen when I remove the top spark plug lead however.<br /><br />Hope this will help lead to a possible solution, as I would _really_ like to resolve this.

 

[OBJ]

Re: Help !! Johnson 50 '84

Hi Mag....from your last post it would appear that the top cylinder is only firing occasionally. The sensor coil is good because the lower cylinder is firing all the time and the power coil is good for the same reason. Only leaves the power pack or coil.<br /><br />Rig a spark tester and test the spark with the power pack connected to the coils normally. You will probably see an intermittent spark on number one cylinder.<br /><br />Now swap the leads from the power pack to the coil. If the top cylinder stays the same, replace the coil to number one cylinder. If the number two cylinder starts firing erratically, replace the power pack. Keep us posted.<br /><br />PS...I have a 84' Johnny 50hp also.

 

[maggun]

Re: Help !! Johnson 50 '84

First of all I would like to thank you guys for giving me some input on this issue, hopefully I/we will be able to resolve it.<br /><br />I will not have the chance to test the procedure you gave me just yet Jim. But I will definitively try it out as soon as I have the chance. And also keep you all posted on the progress. Within next week I hope.<br /><br />Jim: Hopefully you have not experienced any problems with yours ?

 

[maggun]

Re: Help !! Johnson 50 '84

OutboardJim/Anyone else who know's.<br /><br />Won't it cause problems with ignition timing when swapping leads from power pack, to the coils ? The way I figure (With my limited knowledge on this), is that with the swap, cylinder 1 get's timing cylinder 2 should have, and vice versa. I am not doubting your knowledge, I just wonder how it _really_ works, rather than my assumption.<br /><br />Thanks..<br /><br />- Magnus