dlange

the alternator is charging fine. Always over 12. Drive fluid is fine, I check it before every time out. Also, all the connections look good, and I have used contact cleaner on all the ones I can see. Next step will be,

- check exhaust manifold sensor
-and the impeller and water pump

Also, I have checked the diagnostic manual and nothing really matches up. Thanks for all the suggestions.

SDFever

If by chance, the rpm racing and the beep are NOT related, then you could check to see if the foam piece is in the throttle body.

If it's missing, it will race at medium idle in or out of gear and will go away above 1200.

That's its job - to prevent varying engine speeds in the range you are talking about.

SDFever

With regards to the beep, why don't you graph the various parameters and time it with the engine rev?

You may find it that way.

Is the reving fairly consistent? If left in neutral, will it race or rev about the same amount of time every time?

Regardless of how broken up or bound up the impeller could ever become...... There is NO WAY that engine would ever "feel" or notice that type of load. It would idle as normal as no small piece of veined rubber could ever change the rpm of that engine.

dlange

you may be on to something with the foam. The surge is consistent with the beep. thanks

SDFever

If they are related symptoms, the foam will not trip the alarm. The lack of the foam will ONLY cause a racing symptom.

Run it under load with the scanner and graph the sensors.

Check plugs, wires etc. It's real hard to troubleshoot on the internet.

What Merc Scan tool did you use? The DDT can be too slow for certain issues. The symptoms can fall between the refresh rates...

Get someone to help you locally. Good luck -

merctwofive

Check the ignition wires under the dash... after a week of chasing my tail that's what it was.

pstorti

iTrader: (2)

if I remember correctly there is a ground stud on the back of the block that is hidden under the water hose that runs across there, my stud was all corroded and those ground wires weren't making a good connection. I sold my boat a few years ago but I think I am remembering it correctly it was a 2002 28 daytona with 496's

dlange

ok gentleman, ran the boat today and have a update. First the foam was missing, and a new piece fixed the rough idle, and extra noise i had. Sweet. But, I still get and a temporary surge in rpm any place under 1200 rpm with a beep. It sounds just like when you start the boat from key off. Also, it died a few times at idle when shifting. Any suggestions? Thanks for all your help.

SDFever

Check the digital trim limit sender on the starboard side.

FYI - the foam is to prevent a slight & consistent engine race; it does not have anything to do with a "rough" idle but you will notice a difference without it for sure.

dlange

ok new update. Purchased the diacom software to help solve my problem and still cannnot trace it down. The problem engine still does the surge. It is worst at 1000 rpm. At that rpm it will surge and throw a warning beep almost every four or five seconds, its just like when you first start a engine. It will beep, rev up, then come down again. Just like the ecm resetting? I scanned it multiple times, one time it threw map hi, crank sensor, and cam sensor codes, but after clearing them and running again with same issues no codes after? Also, after about 40 minutes of using the diacom software the ecm would not connect to the diacom software anymore so i am stuck for now.

Thanks for all the time and help so far guys, I appreciate the help. Also, this is a idle to 1300 rpm issue only. Fine running above 1500. Sorry about the long post..