MarineEngine.com does not offer troubleshooting assistance or repair advice by email or by telephone.
You are invited to join our public Boat Repair Forum to seek assistance from other members.
You may also visit the Boat Motor Manuals section of our site to obtain a service manual.
Get yourself an OMC Factory Service Manual and it will tell all in there.
They will idle high on muffs and you cannot adjust idle properly on muffs. Engine has to be in water tank or lake as it needs backpressure. Yours may be fine as usually out of water RPM will be around 1300RPM