Idle speed question

[fishhard]

The motor is a 1975 Evinrude 85 H.p. the manual says to set the idle at 600 to 650 rpm when I do this and then replace the engine cover the restricted airflow causes the rpm's to drop to 500 or 550 I know this is not a major issue but out of curiousity when designed was the idle supposed to be measured with the hood on or off?

 

[jbjennings]

Re: Idle speed question

With the hood on it should idle at the stated rpms.
Actually, if it idles really smooth at 550, I'd be glad and leave it at that. I would think you would want it to idle as low as possible without leaning out and sneezing. That should be about 650 but maybe your tach is off 100.
The slower it idles, the better it is on your clutch dogs.
JBJ

 

[Vic.S]

Re: Idle speed question

Are you sure the drop in revs is due to the cover restricting the air flow and not due to exhaust gas leaking in. From a defective gasket below the power-head for example.

If the cover restricts the air flow that much at idle you wont stand much chance of getting it up to max revs out on the water!