Overcharging Mercury 2002 EFI- 200HP

[doctor-wedge]

I am having a little issue with my mercury efi 200hp , 02 alternator-motor. When I get going on the water for a few minutes and get to the higher speeds my boats alarm will kick in , and slow down the boat till the alarm stops. I speed up and the alarm goes off again. I took the boat to a reputable boat dealer with liscenesed mechanics. They told me that the alternator was overcharging and sending a signal to the computer,for safety warning.This diagnosis was done on the mercury diagnostic program available to mercury technicians. I had the alternator taken to be rebuilt at a shop. They phoned me and told me that the alternator is fine with no issues and runs at 14.6 volts under a high load. Any idea what else could casuse overcharging..

[BigSlick]

Voltage regulators. Change email both, it's about 350-400$. Happened to me last year with a girlfriend of mine in 4 footers. Thank God I had a buddy along side to tow us in. The connectors on the yellow wires were burnt. Changed the connectors and regulators in about 45 minutes. My engine is a 1998 though.

[Allimax]

I take it this is a 2002 year motor? I see why Don always asks for the serial #. If that is the case I think this belongs in the 3.0L section. From what I gather you have the newer set up with a seperate alternator that is belt driven. This would make it an internal regulator possibly (regulator inside the alternator unit). If I'm on track so far I would belive the Merc Tecs. These newer ECM's will record information when it happens & hold it so the Tec can pull it out to see what the problem was when it happened even if all is OK now. Most likely the regulator has a problem after it gets hot & testing it on the bench even under load may not have gotten it to the point it fails.
Check the simple things first, battery connections clean & tight? Battery test good with plenty of CCA's? You could also pull up volts on your depth finder/gps and watch the values as you run her and note things when she acts up.

[Props4u2]

I take it this is a 2002 year motor? I see why Don always asks for the serial #. If that is the case I think this belongs in the 3.0L section. From what I gather you have the newer set up with a seperate alternator that is belt driven. This would make it an internal regulator possibly (regulator inside the alternator unit). If I'm on track so far I would belive the Merc Tecs. These newer ECM's will record information when it happens & hold it so the Tec can pull it out to see what the problem was when it happened even if all is OK now. Most likely the regulator has a problem after it gets hot & testing it on the bench even under load may not have gotten it to the point it fails.
Check the simple things first, battery connections clean & tight? Battery test good with plenty of CCA's? You could also pull up volts on your depth finder/gps and watch the values as you run her and note things when she acts up.

Yes the 2002 engine will have an internal regulator in the alternator and if there was a problem with over charging the tech could see it on his CDS under Freeze Frame.
As stated, make sure battery connections are tight.

[Jonestrollingmotor]

Sure by now this has been answered and put to bed so to speak, but the problem is going to be a bad ground on the motor. If the alternator shop ran/tested the alternator, if it had a bad regulator it would show up then. A bad ground will make the regulator think the battery is low and increase the field current causing the alternator to overcharge. Check the battery ground, the ground at the block, the ground strap from the alternator to the block and clean all the connections and surfaces.

[CaptKarl]

following - having alarm problem for no obvious reason of heat and oil... will report back after checking all electrical bits and also cleaning large on board oil tank

[SilverFox579]

No need to follow an 8yr old topic, open a NEW thread for your specific engine including serial number (one engine per topic) so the pros can help with YOUR specific issues.

See the Announcement for more information - Please READ BEFORE Posting

[JOE54]

[CaptKarl]

As suggested above by JONESTROLLINGMOTOR - http://www.bbcboards.net/member.php?u=4458 ; I went through entire system of my Mercury 2001 250XL EFI; all connections cleaned and tightened all grounds and hot leads; previously done were new thermostats, new impeller, new oil tank and sensor; cleaning on board oil for sludge; new fuel/water seperators; new heat sensors and alarms still occurred about 3000RPM; after wiring checks made the alarms now came at 1800RPMS ... so things got worse (better?) ; now to eliminate over-charging as alarm source the small sending wire from alternator was disconnected and NO ALARM at any RPM - Problem fixed? maybe... the voltage meter on dash with wire on had been indicating higher than normal output; with wire off it needle sat at 14 showing charged battery reading; re-connecting the sender wire the motor again made NO ALARM at any RPM but now meter shows normal output - SO alarm Problem all along was NOT heat, oil, block water pressure, oil pick up, oil tank, water in fuel... it was a LOOSE or Bad connection at alternator sending wire.... $$$$$ for a loose wire. It was like sex... better than sex to get this resolved...HAPPY DAYS ARE HERE AGAIN!!

[CaptKarl]

wilco to new thread - i found this old thread as may others and it helped immensely...