99 mercruser 502 loping in idle??

[hammer250v8]

i just bot this boat and it has a 502 mercruser. this is my first inboard motor. the problem is when it's cold or after it hasn't been started for a few days it will lope up and down till it warms up good. plugs are new, fresh oil and filter and fuel filter. fuel is fresh with pri-g additive. i dropped it at the local dealer to fix but learned a few days later when i called that they are 3 weeks behind! i'm going to pick the boat up today and hopefully with the help from this baord et it figured out. i think it may be the MAP sensor. thanks for any help...james

 

[Don S]

Re: 99 mercruser 502 loping in idle??

Have you tried a good ole tune up. Cap, Rotor, and spark plugs?? Can we assume you have EFI?

 

[hammer250v8]

Re: 99 mercruser 502 loping in idle??

it looks like it has new wires on it. i pulled a few pulgs and the look new. it runs strong above idle. i'll pull the cap off and check it out...james

 

[newport dave]

Re: 99 mercruser 502 loping in idle??

RPM variations like that can be caused by a few different things and even with the right diagnostic equipment can be tricky to diagnose. I would have someone look at it. It's usuallly not something serious, but I have seen this symptom on engines that were starting to ingest water due to bad manifolds/riser gaskets.<br /><br />Dave

 

[llerrad]

Re: 99 mercruser 502 loping in idle??

Try vaccum gauge to check low idle adj. screw setting at carb. Research web sites for correct setting and adj. method.

 

[llerrad]

Re: 99 mercruser 502 loping in idle??

Oh ya if you have EFI check for vaccum leak.