Idle RPM's for Merc OB??

I have a 2000 50HP ELPTO Mercury OB. Question.

1. What should the RPM's read while in neutral and at idle?

I used a drum first full of water (to get the exhaust pressure) and ran the motor, and the RPM's are running between 1000-1200.

Without a DRUM and using the flush ears, it rumps up to 2000 RPMs. I expected it would do this.

My service manual (if I am reading it correctly) says this:



It says about 675+- 25 RPMs. When I adjust to get that low it the motor dies. The OB seems to idle OK around 950-1100 RPM mark. Other than that, it seems fine. Any input on this? Leave it alone, or is the RPMs to high for idle? Don't most OB's run pretty high while idling???

Fatten up the idle air/fuel screw to drop RPM a little on muffs. Tune it at the lake in gear (be carful) so it won't stall going in foward and reverse. The numbers are a suggestion so it does not bang or clunk into gear and not stall. Find your happy place and move on. I go as low as I can unless stalling in current or crowded boat launches is dangerouse.

It is not good for the gear case to engage at such a high r.p.m. You should drain some of the gear oil and make sure there is no metal bits.
Poor idle can be caused by any number of things.You can try adjusting the idle mixture making sure not to have it too lean(keep it within spec.)

Before tearing into the carb or doing a link and sync you may want to run the motor from a separate fuel tank and line with fresh fuel or better yet directly to the carb(pre-mix) and before oil injection(fresh fuel) to eliminate the fuel system.

If you want to use your motor in the mean time you can adjust your idle speed down and use the fast idle lever to keep it running turn it down and let the rpms drop and put it gear hopefully without stalling.Check your plugs if you suspect your motor is running lean or hot it should be serviced.

Thanks for the suggestions. I am taking her out next weekend on the lake just to see how she reacts on the water. Carbs were cleaned and gaskets replaced last July. Gas is new. I'll look at the lower unit grease. She doesn't stall when putting into gear, just the RPM's are kinda high for my liking. I did have to play with the idle mixture a bit last year, and think it may have to be adjusted a bit. I'll keep this thread open to report back my findings or if I have more questions. Thanks for the feedback.

675 is the factory specification.

If it won't go to 700 without stalling, it has problems. Carbs, air leak, timing, synchronization issue, fuel quality issue, could be a million things causing it but it should easily go 700rpm or a little less without problem. I remember messing with them years ago and when set properly, they'll idle clear down to around 550-600 and stay running. They'd go lower but get iffy below about 500.

In water vs out of water doesn't make a huge difference if the carb's are set correctly. Maybe 25-50rpm at most.