60hp 1990 2-stroke Johnson idles too fast

[rebars1]

New to me boat with a 60HP 1990 Johnson: When I start the engine (on muffs) it runs at 2000rpm and will not rev down (it will rev up). I was told the carbs were rebuilt shortly before I got it but I don't know if the boat was run after the rebuild. I loosened the throttle cam flollower and checked that all three throttle plates were closed, however, even with all throttle plates closed it still runs at the high speed. Since the carb cam does not engage until the motor is put into gear, is there another adjustment to make? (there is a threaded adjustment screw on the throttle cable, and I see two large springed screws above and below the pivot point of a lever that the cable attaches to).

I grabbed a Seloc manual to get me going, but I have not found this problem in it. I'll be ordering the facotry manual.

Any help would be appreciated.

 

[rebars1]

Re: 60hp 1990 2-stroke Johnson idles too fast

I got the idle down to 1100 rpm (on muffs) by turning the adjustment screw on the throttle cable and backing off the spring screw on the lever it attaches to. I am not able to adjust the cable any further due to running out of threads. I think I am supposed to get it down to about 600-700 rpm but am not sure how......?

Here is another question: The manual says the idle should be around 600-700 rpm, but I think that is in the water, under way. Would that translate to a higher rpm on muffs?

Sorry for all the questions, I have had more experience with Mercruisers V8.

 

[roger3645]

Re: 60hp 1990 2-stroke Johnson idles too fast

Check to make sure carb linkage is not sticking. Also check idle timing maybe be advanced too much, also check idle stop screw. Also check idle mixture screws on each carb check manual to see how many turns they should be out from a lightly seated position.

 

[rebars1]

Re: 60hp 1990 2-stroke Johnson idles too fast

Thanks for the response.

Can you clarify what the idle RPM's should be when running on muffs? Is 1100 rpm too fast?

 

[airframer]

Re: 60hp 1990 2-stroke Johnson idles too fast

without that back pressure its going to idle fast. try putting it in the lake on the trailor. i bet the idle speed drops to where you need it just from adjusting the tower screw like you had before.

 

[rickdb1boat]

Re: 60hp 1990 2-stroke Johnson idles too fast

1100 is a bit fast, even on muffs. I would shoot for no more than 1000 on the muffs and 700-750 in gear on the water..

 

[rebars1]

Re: 60hp 1990 2-stroke Johnson idles too fast

My son and I took it down to the harbor and floated attachd to the trailer and started it up. The load from being in the water made a big difference and I had to adjust it up to keep it running. Next we'll do the idle speed adjustment while under way and see how that goes.

I think I'll also do a compression test and spark plug (pull the wire off) test to make sure all three cylinders are working.