Idle adjustment

[steviecops]

I have a 1980 Johnson 55, 2 cylinder. My engine seems to be idling too slow, although it does keep running and is fine at all other speeds.<br /><br />I've learnt, through this board, that I should adjust the idle speed to 750 rpm, with the boat on the water and the engine in forward.<br /><br />Is it alright to adjust the idle speed with the engine running in a water butt whilst in gear? Would the load on the engine be the same as it would be with the boat on the water?<br /><br />Finally, what is it exactly that I must adjust? Is it the idle jet, the timing or the little wheel that is fitted on my throttle cable?<br /><br />I would be very grateful of any advice and information on this subject, including description and whereabouts of the idle jet, etc, etc.<br /><br />Many thanks in advance<br />Steve

 

[steviecops]

Re: Idle adjustment

Any info at all guys? I was hoping to have a go at it tomorrow.<br /><br />Thanks.<br />Steve

 

[rickdb1boat]

Re: Idle adjustment

If you don't have an actual idle adjustment screw, adjust the trunion nut(little wheel) a bit to raise the idle. Idle mixture screws should be turned out from a lightly seated position and backed out 2 turns to start and go from there until it runs best at idle. You don't want it higher than 800 RPM's while in gear on the water in gear.

 

[steviecops]

Re: Idle adjustment

Thanks a lot Rick.<br /><br />I'll give it a go tomorow and see how It goes from there.

 

[steviecops]

Re: Idle adjustment

Didn't get to adjust anything today, as I discovered that my engine had NGK spark plugs fitted. Another thing I've learned through this board is that OMC engines were designed to use Champion spark plugs, so I spent the rest of the day tracking down the correct plugs.<br /><br />Is it possible that my engine has been idling poorly because of the NGK plugs?<br /><br />I'll fit the Champions tomorrow and then make any necessary adjustments.

 

[jimchere]

Re: Idle adjustment

I ran NGK plugs in mine ('82 rude 55hp) for about 20 hours then changed to champion plugs during a tuneup after reading on this board.<br />The NGKs ran okay, but the idle did seem a bit smoother and better response with champions. Granted, my experience with NGKs was only about 20 hours. I wouldn't say that the NGKs are incompatible, just that the 'rude does seem to like the champion plugs a little better. Darnit another edit: Also have to add that the reason it ran a little better may also have to do with the minor tuneup more than anything else.

 

[steviecops]

Re: Idle adjustment

Jimchere<br />I have only recently bought the boat and engine, so I have only run it a few times with the NGK's. It does run fine at all other speeds, so the NGK's must be O.K, just that the idle is a little rough and I thought before I go fiddling with things, I ought to try the Champions.<br /><br />If they seem to have improved things, I'l post the results on here.<br /><br />Cheers<br />Steve

 

[rickdb1boat]

Re: Idle adjustment

Use Champion plug QL77JC4(Resister Plug) or L77JC4's gapped at .030. Same heat range. Walmart will have them for a couple of bucks.

 

[jimchere]

Re: Idle adjustment

One more thing to think about. Your idle on the muffs from the garden hose will be a bit higher than in the water because of the backpressure on the exhaust. I'm no expert, but in think the 55hp in this year vintage is a commercial/military version, and mine has carbs with no idle adjustment. All the adjustments at idle are done either with the cable screw trunnion nut or the idle timing.<br />Not being an expert, I will stop here and hope that maybe someone of the likes of Joe Reeves stops by. Another thread I need to start is to ask someone like Joe what the idle timing should be, as my Clymer manual is only semi-useful for this engine.

 

[steviecops]

Re: Idle adjustment

Rick. Got the QL77JC4 plugs today, and will fit them tomorrow.<br /><br />Jimchere. I've looked all round my Carbs, and can't find any idle mixture screws anywhere. Like you say, I think the idle speed has to be adjusted using trunion wheel or timing.<br /><br />I'm going to run my engine in a large water butt whilst making any adjustments. I'm hoping that if I also put the engine in gear, it will load the engine the same as if I had the boat on the water in forward gear.<br /><br />Thats my theory anyway ;o) If anyone knows different, I'd be glad to hear from you ;o)

 

[AUGIDAWG]

Re: Idle adjustment

If you fill your large butt with water, you might end up with messy results.

 

[R.Johnson]

Re: Idle adjustment

My 1980 OMC service manual shows this engine to be a 60hp twin. This engine has a idle stop screw as most all OMC engines have. It is located on the large link arm on the strbd. side of the block. Adjust this screw with the engine under load. To make this engine idle properly, you must do a complete sync & link process. The trottle cable trunnion is part of this process. It is not meant to be used as an idle stop. It is used to adjust cable to insure idle stop screw is against it's stop at idle, and carb's are wide open at full throttle. The 1980 60hp has a idle speed needle located on the right hand top of the carb. You would adjust this after all other adjustments are correct. This large twin engine is not noted for it's idle quality. If the engine shifts smoothly, and idle's with out stalling, it is probably correct.

 

[steviecops]

Re: Idle adjustment

R.Johnson<br />Thanks for your invaluable advice.<br /><br />My engine will idle all day long without stalling, and the gears shift very smoothly. It just seems to jump around a bit when idling, which lead me to believe that the idle speed was too low. But from what you've said, I'd better leave it well alone, as it seems to right for the engine.<br /><br />Thanks again<br />Steve

 

[jimchere]

Re: Idle adjustment

Even when perfectly tweaked, verified compression, et.al. mine still "jumps a bit" at idle; never has nor never will idle perfectly. I'm not saying it idles like crap, just not a perfect sound. I think like someone mentioned above it is typical for these engines. When I take her just above idle (1100 RPM or so) it purrs like a kitten, very smooth (in my 16' boat, that's about 4-5 miles per hour). Has lots of power/holeshot, doesn't run hot, and starts great. Plugs look great everytime I check them.<br />Just accept it as a small fault in an overall durable and reliable motor, in my opinion, if running great and idling as you described.