Johnson idles too fast and timing is strange

[tinhog69]

I have a Johnson 70 which is having problems. When it is not in gear it idles at 1100 to 1300 rpm. When put in gear at idle it goes to 900. The manual says it should idle at 600 to 700 when put in gear and the timing is adjusted on the lake in gear at idle speed. <br /><br />After inspecting the engine I found that the throttle linkage was not set up properly. The throttle arm was not set against the its idle stop. I adjusted that and the throttle cam and throttle cam follower to .010inches. I took it on the lake to see if this made any difference and to check the idle timing. The idle timing was set to -4 degrees and the spec was 4 (ATDC). I changed it to 4 and adjusted the idle mixture. It idled ok but would not accelerate at all. It bogged big time when trying to advance the throttle even out of gear. The idle was 900 rpm after all of the adjustments, the same as before. I changed the timing back to as it was. <br /><br />The thing that is concerning is the manual mentions if the idle is too fast there could be a leak to check induction system for air leaks. How do I do that and is 900 rpm too fast for this motor in gear? And the timing is 8 degrees off and runs good above 1500 rpm? Any chance of damage? <br />I am going to buy a tool to insure the timing pointer is at the correct location so when it indicates it at a particular timing it is correct. This tools checks top dead center of piston # 1.

 

[ICEMAN]

Re: Johnson idles too fast and timing is strange

HI, What year 70 hp? Model number please

 

[tinhog69]

Re: Johnson idles too fast and timing is strange

Iceman,<br /><br />The year is 1999 and model # J70PLSSD

 

[jegervais]

Re: Johnson idles too fast and timing is strange

You've got a 2000 model. The idle speed spac is 800 +/- 50 rpm's in gear, in the water, boat unrestrained. Make sure all throttle plates are completely closed when setting the carb linkage up. Loosen all the linkage screws and tighten the bottom one first (hold up on the link as you tighten the screw), than do the top one. Make any carb (idle needle) adjustments in the water, not on the hose.<br /><br />I'm unsure about your timing description, please clarify for me. When you look at the timing grid on the flywheel you see (left to right):<br /><br />BTDC 24 20 18 16 14 12 10 8 6 4 2 TDC 2 4 6 ATDC<br /><br />The spec is "bold" in my example, is this what you've got it set to?<br /><br />-John

 

[tinhog69]

Re: Johnson idles too fast and timing is strange

John from Illinois<br /><br />The numbers/letter on the flywheel from left to right are:<br /><br />28 20 12 4 T -4 <br /><br />There are no letters for BTDC or ATDC and no numbers for -6 and -8 but there are marks. <br /><br />When I checked the timing it was -4. Compared to your example -4 is equivalent to your 4 ATDC. Is that correct? The idle speed is 900 or 875 with the boat at idle, in gear, with the boat unrestrained. So that must be ok given your info.. Let me know if the above is not a correct assumption. <br /><br />My original problem and still is it dies after putting in gear and advancing the throttle. If I can get past 1500 rpm it runs great, usually after several tries. The problem goes away after warming up and keeping the engine going. After sitting for 5 or more minutes the problem is back and takes several tries to get over 1500 rpm with out dieing. Funny thing is that when the boat is first put on the water it is ok. After that it only runs good after running and kept running. <br /><br />I did a carb overhaul and going to test it today. The carbs looked clean, no gum, varnish, or plugged holes. If this doesn't take care of it do you think the VRO system maybe a problem? I saw in other postings some guys took their VRO system off and helped a problem similiar to this.<br /><br />much thanks!

 

[jegervais]

Re: Johnson idles too fast and timing is strange

Yes, -4 = 4 ATDC, I wasn't certain if that's where you had it. Are you able to, or have you done a compression test. Your idle speed is a touch high and that engine doesn't stall like that...<br /><br />The vro is also your fuel pump, if fuel pressure is low, it might be part of, if not the problem.<br /><br />-John

 

[tinhog69]

Re: Johnson idles too fast and timing is strange

John,<br /><br />Took the boat out and tested the carb rebuild. No difference. Also shutoff the oil supply and used aux. tank with 50 to 1 mix. NO change. Even ran the boat with the 50 to 1 and the oil tank line connected,No change. <br /><br />Only thing that was noticed (sometimes worked) if I momentary pushed the choke for a split second it did not bog (die)when advancing the throttle in gear. The other thing that worked sometimes if I put it in gear and push the throtte forward quickly enough (3/8 inch) to get thru the 1500 rpm bog area when the motor is cold. There is a little bog sound but gets thru the bog area. <br /><br />If it is the fuel pump shouldn't wouldn't there be more problem with high speed and not at takeoff?<br /><br />The problem is really noticable when the engine has sat for about 5 minutes and engine put in gear and the throttle very slowly advanced. Dies like a mother then. Worse when the engine is put in reverse. <br /><br />So far I have tried (not in order):<br /><br />1. carb rebuild <br />2. adjusted throttle linkage<br />3. adjusted throttle cam and roller to .010 inch<br />4. new gas in aux tank<br />5. disconnected oil supply and used aux. tank with 50 to 1 mix<br />6. checked idle timing<br />7. sea foam carb cleaner gas additive<br />8. new plugs<br />9. adjusted idle mixture<br />9. engine checked over by boat shop. They thought they had the engine fixed. Ran good in the test tank. <br /><br />Have not tried a new prop. The one on it is a 15 degree. Boat gets up and plane pretty good with this one. <br /><br />The boat shop did a compression test and said it was fine. <br /><br />If it is the fuel pump shouldn't wouldn't there be more problem with high speed and not at takeoff?<br /><br />Any possibility of a temp controller or thermostat being a problem?<br /><br />It was explained to me to turn in idle mixture screw until it died and back off 1/4 turn. It really did not like to idle at that so I backed off an additional 1/4 turn. Is the best way?<br /><br />If the throttle cam and roller was off (greater than .010 would this make it do this?<br /><br />thanks for the help

 

[Brian L]

Re: Johnson idles too fast and timing is strange

Hey Tinhog69,<br /><br /> All my suggestions you have allready covered and actually some I would have not even thought of, so I am sorry I cant help out....but I really am intrested in what is going on with your motor. Sounds like you have one of those "ghost" problems that haunts you till your blue in the face, and you cant find what it is. I feel for you..... I would like to know what it was when you finnaly get an answer, in the mean time I will ask around too on some other bulletins. Well good luck, and please let me know what it turns out to be. <br /><br />blowell@clcats.com<br />Thanks, Brian

 

[jegervais]

Re: Johnson idles too fast and timing is strange

Is the ignition timing advancing as you advance the throttle?? Are all the throttle plates 100% COMPLETELY closed when idling??<br /><br />-John

 

[tinhog69]

Re: Johnson idles too fast and timing is strange

John,<br /><br />The butterfly valves look 100% closed to me. <br />I don't know about the advancing. I will check next time. <br /><br />Looking at the engine this morning I found that when you screw in the slow speed needle that when they seem seated they really are out 1 turn. The spring does not allow the screw to seat before backing out for the 2 3/4 turn out start point. When the spring is fully compressed it keeps the screw out about 1/2 to 1 turn. Maybe the carbs were not all the same for slow speed setting. Two of them may have been off by 1/2 to 1 1/2 turn from each other. I don't know if having the carbs 1/2 to 1 1/2 turn different from each other would do this. <br /><br />Going to test this Weds. or Thurs.. <br /><br />Any other ideas or suggestions welcomed or comments on above welcomed <br /><br />thanks!

 

[Franki]

Re: Johnson idles too fast and timing is strange

The way I was always taught to set the mixture is pretty simple..<br /><br />Set it 2 turns out(from fully in position).. then start the motor..<br /><br />slowly screw it in until the motor dies or bogs right down..<br />count how many turns in it too to reach that point. (from its two turns out position)<br /><br />then put it back at two turns, and start again..<br /><br />when screw it out until the motor starts dying again.. again count how many turns out from the "standard" two turns you started with..<br /><br />now you have to find the middle point between the two (inner position and outer position) and set the mixture there,, its not perfect, but its not that far off the mark.<br /><br />obviously its easier on single cylinder motors, but it can work on multiple cyl's..<br /><br />perhaps you should give that a go.. <br /><br />regards<br /><br />frank.

 

[Franki]

Re: Johnson idles too fast and timing is strange

The way I was always taught to set the mixture is pretty simple..<br /><br />Set it 2 turns out(from fully in position).. then start the motor..<br /><br />slowly screw it in until the motor dies or bogs right down..<br />count how many turns in it too to reach that point. (from its two turns out position)<br /><br />then put it back at two turns, and start again..<br /><br />when screw it out until the motor starts dying again.. again count how many turns out from the "standard" two turns you started with..<br /><br />now you have to find the middle point between the two (inner position and outer position) and set the mixture there,, its not perfect, but its not that far off the mark.<br /><br />obviously its easier on single cylinder motors, but it can work on multiple cyl's..<br /><br />perhaps you should give that a go.. <br /><br />regards<br /><br />frank.