Tuning of mixture

[Groot Brak]

I have a 1976 35Hp Johnson. Inside the engine you get the mixture adjustment. I leave my cover off the engine for a day or so after being on the water just to dry off things. Now my mixture adjustment got turned and turned and turned by the little people. <br />I don't know where to reset it. I've been told to adjust it until it idles the fastest speed for a fixed throttle. I've been told "right in the middle" I've heard "until it change speed leaner and then back until it change speed ritcher and then halfway back." I have to have someone run the boat at full speed on open water and adjust it until I get the best speed. If the plugs's condition is the key as I was told as well, then the plugs is fairly clean, but with little round blops of carbon and the anode a bit thinner than new. (BTW, I don't know what the excact spark gap should be as well...)That tells me it could be too lean. (I think.) Right now while cold the engine tend to cough and die at idle speeds.<br />All in all, I don't know. Please help cause I don't want to mess up the engine!<br />O yes, and should I use leaded or unleaded fuel and at what octane? I mean this could surely change the fuel/air mixture, right?

 

[OBJ]

Re: Tuning of mixture

Hey Groot, here's what ya' need to do....<br /><br />Turn the needle in till it JUST seats. Don't force it. Back it out 1 1/2 turns. Start the engine and warm it up to ops temp. Put it in gear. Adjust the needle, usually in, about 1/8 turn till the highest and smoothest idle is obtained. Allow 15 to 20 secs' between adjustments. Back out a little, this is to keep it from running to lean. You will be able to hear the engine respond if the carb is in good shape.

 

[rolmops]

Re: Tuning of mixture

Hello Groot.<br />Everything that was said in the first post is good advice.I'd like to add that you should do these adjustments in the water while moving forward.Not in your driveway on the hose.<br />As for your plugs,They should be champion plugs.I think J6C.The distance should be 0.030 inch,which translates into your 0.762 mm.However you should double check these numbers because my manual only goes up to 1972.Unleaded gas is fine and 87 octane is good enough. Although higher octane will not hurt any,it will do you no good either.Just make sure to use a good mixing oil for water cooled engines (TC-W3)and a 1:50 mix.<br />Good luck.

 

[OBJ]

Re: Tuning of mixture

Git a load of this rolmops.....my parts book says and that's with running the suppercedes....the correcto plug for that 35 is a UL81J. The very next year it went to a L77J4 and of course the latest QL77JC4. Go figure... I'm at home but am going to look at the latest P&A book and see what it say. Hang in there Groot....we'll find the right plug yet!

 

[Groot Brak]

Re: Tuning of mixture

Thanx. I'm not 100% sure by the meaning "until it seats" I suppose that is all the way in, i.e. towards leaner? That be the case, then I'm 2 turns back from there, as most posts on the topic suggested. Did not try out the adjusting bit while in gear, though. The current plugs is B9HS10 from NGK.<br />The lowest (only) unleaded octane we can get is 95. Leaded is 93 and 98. Been mixing 1:40 on advice to mix more oil because its safer. Been a bit of a smoker...<br /><br />Took the boat out yesterday, and it started and run smooth. I stripped the carb just before we went out, and it was as clean as a whistle. I found the missing screw as well. After the last trip a screw was just laying in the engine. When I took the carb off, I got the missing screw, boy. Good thing I took it off even though it was clean...<br /><br />Had one problem yesterday. After running around, switching on and offa lot of times, the engine was still OK. At one stage, I stalled the engine, (on a sand spit...) and it refused to restart. The primer bulb was emty even though I restarted immediatly. After that I switched on and off at least three times with no hassles at all. As I was taking the boat out, I accidently started the boat in gear and throwing it into neutral it stalled. Afer that it refused to start. Even back home nothing happened. The engine cranked but it did not start. Fuel was ok, as I wanted to check for spark, it fired up. Did not touch a thing before that. I tried to check the ignition switch wiring as I suspect the problem could be there and the engine was running. The damn thing gave me a very big shock!!! It was hi tension sitting there, not the usual 12V jolts. It was just as bad as holding a plug wire in your hand while running the engine. It was the same spiky feeling as a life plug wire. How is that possible? Surely it can't be. I mean 12V should be the max on the ignition? I've never shocked before with the boat, except directly on the plug wire and the gentle tingle of 12V while pulling battery clamps off standing in the water. This was bad. Was it just some water somewhere or could this be a wiring fault?

 

[OBJ]

Re: Tuning of mixture

Hey groot.....The correct spark plug for the engine is a UL81C, set at .030. If it were me, I'd put the correct Champion plug in it.<br /><br />A "shocking" experience, eh? If you were fumbling around the ignition switch terminals with the engine running, you probably got across the battery and ground posts. I've done this once. Wakes ya' up.

 

[Groot Brak]

Re: Tuning of mixture

Nah, that shock was not coming from the battery. 12V won't do it for me. It was hi-voltage pulsing power. Just grab a plug wire next time you run your engine, that's what it was. I found a wire cable-tied to the one plug wire. I have a hunch that some of the spark was thrown through there to my ignition switch. I removed it now. That could be the reason the engine did not start as well. Hav'nt tested it again yet! That could be the reason the engine did not start as well.<br /><br />Was doing a gearbox oil change, but forgot to buy some more oil , so there won't be much running the engine until Monday, maybe Sunday. Going on a course from tomorrow till Sunday.

 

[Bass Runner]

Re: Tuning of mixture

If i remember right your motor has factory presets and you can only adjust the jets about a half a turn or so, so it can't be to far out of adjustment, if it dosn't have presets on it or someone has taken them off here's how it goes, idle jet gently seat the needle then turn out 1 1/2 turns, high speed gently seat and turn out 1 turn, fire up the motor in the water not muffs or barrel after warm up adjust low speed out untill you are satisfied with the idle let it run a few min to make sure it dosn't load up to much then take it out and run wot adjust high speep for best performance and you are back to drinking beer and having fun.