Idle Rpm

[Captain1175]

Took out the boat today, 1st time since replacement. 1984 75 Merc. Boat ran fine 7 to 10 runs about a mile each. Get back to dock, turned off to load, when I went to fire back up it took its time to start and once it did when I went in gear it stalled, finally got it on trailer by hitting hard on throttle. Here are my other symptoms that I think may be an issue. First of all the 75 had been sitting for a year, did the sea-foam treatment, 2nd and I think is defiantly a problem at Idle my Rpms are about 1300 -1500, I would assume too high. I know a carb job is in order but is there something else I should check before a tear down, which I will no doubt do in near future, just want to fish for a few weeks while weather is still good (Ga.). Finally what about the high Rpms could i just adjust Idle stop screw.

 

[oldman570]

Re: Idle Rpm

The motor shoul idle at 700 to800 in FWD and will run up when not in FWD. If the motor wants to stall when putting in FWD then the carbs are needing attention. I would get a can of Mercury Power Tune or Omc Power Tune and try to clean the carbs without taking them off first. Best done by disconnecting the fuel line at the carb and spraying it in the carb till it foams up in the carb throat. Also put in the Idle jet after counting turns of the jet to lightly seated then remove the jet and replace it after spraying in the jet itself. Do this to each carb one at a time before moveing to the next carb. Replace all fuel lines to carbs and leave it set for 20 min. then prime the bulb and fire it up. It will smoke quite a bid till all the Power Tune is gone. Then hit the water and see if it helped or more work is needed. JMO
Oldman570

 

[Captain1175]

Re: Idle Rpm

It does seem to calm down once I move the throttle, so the way to check Idle is when in fwd gear , not just at rest with motor running

 

[oldman570]

Re: Idle Rpm

That is correct Capt. The Idle RPM on all motors needs to be set with the motor in FWD and in a test tank or in the water and not on muffs. With the motor on muffs there is no backpressure and resitance of the prop trying to push the water as it would do on the water. Hope this explains things better.
Oldman570