high idle

[73SCTsunami]

This winter I bought a 94 merc 225 (carbed). Running it on earmuffs in the driveway the idle rpm is around 1500. Is that normal? I would have expected about half that but I wonder if it's due to the lack of back pressure on the exhuast. Also when I try to move the throttle up, the RPMs won't hold steady, they're moving up and down quite a bit. I have no idea what might be causing that. One plug wire looked to be corroded so I'm replacing the set but other than that, I'm at a loss. It starts right up, very easily.<br /><br />Any advice would be appreciated...service manual is on order.

 

[andy6374]

Re: high idle

You are correct, the motor will idle higher with no back pressure. Plus if the motor was cold it idles a bit higher until it warms up.<br /><br />Sounds like you are losing spark. Replace the plugs wires and see if that helps. If it still has problems...while it is acting up have a friend check for spark on all cylinders with a timing light.

 

[73SCTsunami]

Re: high idle

That's what I was hoping to hear. The bottom plugs on each cylinder bank were pretty corroded and although you can't see in to the boots too well I have to assume the contacts on the wires are in bad shape too.<br /><br />I'll get new wires in this weekend, might be abother week or two until I get to water test though.<br /><br />Thanks again.