High idle with cover off

New to the small engine world, so this may be a dumb questions.

I have a 1977 55 HP Evinrude (55773D) that I recently purchased. I have noticed that it idles fine with the engine cover on, but the rpm's pick up considerably with the cover off. Is this normal, and if not what should I be looking at?

On a side note, it looks like everything on this boat was done half-assed, so I'm assuming the preventative maintenance on the motor was lacking. What's the top couple of items that I should inspect/replace to start with?

Thanks in advance,

Sam

Is the motor running in a barrel ??----------------Replace the water pump impeller if you do not know how old it is.----Test the hot horn in the control box too.

exhaust leak and adjusted to overcome it? how does the motor run on the water at running rpm with the cover on and off?

I was running the motor in the driveway hooked up to a garden hose. I wasn't able to get out on the water to test this weekend, but will try on Tuesday night and report back.

Thanks!

I got out on the water yesterday, and it idles the same with and without the cover. The idle speed was somewhere between the high and low idle seen when hooked up to the hose, but seemed a little high overall.

Adjust cable or idle stop screw to make it idle at a " happy speed " so it does not stall when shifted.