Carb adjustment?

[drwet]

I have a 1972 Johnson 85 that I am returning to service after sitting for about 10 years. I've had the carbs off and rebuilt them. (There are two two barrel carbs.) The manual I have makes no mention of any slow speed adjustment, but the silencer box has four plugs labelled slow speed adjustment which line up with screws on the carbs. When I took the carbs apart these screws were loose by anywhere from 1 to 3 turns. I spent a couple of hours searching this forum and found very detailed instructions on how to adjust these slow speed screws. I also found a couple of postings that said there is no adjustment on these carbs and that these screws should be turned down tight. I should add that these screws are not needle valves. They are about 3/4" long and flat on the end, so I don't see what good it would do to adjust them. So, what's the story? Do I set these things at 1 1/2 turns out, or just wind them in tight?

 

[5150abf]

Re: Carb adjustment?

I could be wrong but on a 72 the carbs were still adjustable, they went to fixxed jets @80, so ya start at the 1 1/2 turns and adjut from there.

 

[drwet]

Re: Carb adjustment?

So what does it do when I adjust those screws? There is no needle on the end of them. They are just a square ended screw. I can't see any way the air fuel mixture will change by adjusting these things.

 

[64osby]

Re: Carb adjustment?

FR had stated this = in a link that was in the TOP secrect file about carb ajustment, http://forums.iboats.com/showthread.php?t=244013

The idle metering jets are in the holes behind the screws that you removed from the outside, to the right and left of the core plugs. Don't mix up any of the jets, put them back in the same holes you got them out of.

I have a 74 rude, and when I look at the manual there is a low speed orifice plug, or jet, in the hole that you removed the screws from. These are listed as fixed low speed jets. I don't think there is an adjustment, you just want to make sure it is clean. They require a special tool or homemade one that is shown in the link above.

I have not rebuilt my carbs since I picked up my motor just before the snow started flying, but I'm sure come summer I'll be messing with it like you are now. So then I'll be askin the questions and you can tell me how it's done.

Good Luck

 

[jtexas]

Re: Carb adjustment?

Those are "screw plugs", they need to be in tight. Airbox cover is probably a common part with the '71, which had adjustable carbs.

There are lots of fixed-jet carbs on pre-80 OMC motors.

 

[emdsapmgr]

Re: Carb adjustment?

The last year for the idle screws was 1971. My 72 did not have adjustable idle jets and the 1972 factory parts list shows fixed jets for the idle on these carbs. It is likely that OMC reused an older type airbox cover in model year 72, from the earlier models (1971) which had idle adjustment screws. You might want to confirm the year of your engine, based on the model number if it's a 72 85 hp, the model number should be: 85ESL72R. You can see the factory parts list for your engine and carbs at: epc.brp.com. The idle jets are fixed on these carbs and all later carbs. The idle speed on the 72 is set by adjusting the idle timing and has nothing to do with the carb settings. When at idle, the carb butterflys are closed and the fuel enters the carb throats thru special idle passages. Though the idle timing adjusts the idle speed, it is still important that the dedicated idle passages in the carb bodies are clear of dried fuel and any debris for proper fuel flow (and smooth idle.)

 

[wilde1j]

Re: Carb adjustment?

If your talking about #24, they just hold the inner airbox in place. I don't see any sign of idle mix adjustments.