Trouble with 496 HO!
 

I've got a 2004 496 HO thats setting off the warning buzzer every 60 secs from idle up to 4600 rpm. If you accelerate hard or go over 4600 the alarm is constant until you return below 1500 rpms. Then it returns to the every 60 sec beep. The smarcraft guage displays the engine icon and bell icon flashing on the screen. All gauges are normal and the drive bottle is full. Any ideas?

Re: Trouble with 496 HO!
 

I had a similar problem with one of mine. It turned out to be a bad oil pressure sending unit. Easy fix. Put a DDT on it to see what code it is sending. That will tell you.

Re: Trouble with 496 HO!
 

Just so you 496 owners know, Rinda Technologies in Chicago sells a simple DDT scan tool you can hook up to your harness and read any trouble codes. It will also let you clear the codes when the problem is cleared or repaired.
I am sure a visit or two to your dealer, plus your time to take the boat in will cover the cost about $300 real quick.
Ray @ Raylar

Re: Trouble with 496 HO!
 

Thanks Raylar! Called them and the price is $399.00 plus $39.00 for the PCM 555 adapter. Just gonna swing buy a dealer and have them read the codes.

Re: Trouble with 496 HO!
 

I agree with Raylar, having the scan tool will save you allot of headaches, and money in the long run. There are way to many faults that can give you the warnings you are talking about to make an educated guess. I recomend this for anyone who has a PCM 555 engine. Mercury also has a PCM 555 service manual, I believe is manual #33, that has been useful in troubleshooting. Since having this engine I have had to replace, an IAC valve, waterpump, and a MAP sensor. All showed up on the scan tool as hard faults. Good luck, let us know what you find.

Re: Trouble with 496 HO!
 

Hooked up the DDT today and heres what was on it.

Fault Active menu

Pitot CKT LO Yes
Fuel LVL CKT HI Yes
Steer CKT HI Yes
Fuel LVL2 CKT Yes

Freeze Frame Buffers

0- Fuel LVLL2 CKT H
1- Steer CKT HI
2- Fuel LVL CKT HI
3- Pitot CKT LO
4- IAC output
5- Crank SNSR
6- Cam SNSR

Any ideas?

Re: Trouble with 496 HO!
 

Alli,
0- Fuel LVLL2 CKT H
1- Steer CKT HI
2- Fuel LVL CKT HI
3- Pitot CKT LO
These are codes that will always show up being they are unused in most set-ups. None of these are engine related. These would be used for fuel tank levels, speedometer, and steering position. They will always show faults because they are generally not hooked up. They are also not tied into the guardian, or warning system.

However, these can very well cause a problem.
4- IAC output
5- Crank SNSR
6- Cam SNSR
I just recently had the IAC output fault myself, resulting in an IAC motor change. About 70 dollars. But before I went there, I would erase the codes and try it again. In my case the IAC was an active fault at all times. None of the active faults you have shown will cause the guardian warning. Although I have heard people having a hard Crank, or Cam SNSR fault, requiring replacement, I have not yet to come across this as a hard fault, but I will get these this faults locked in on occasion. This tends to happen on occasion during engine start, and lock in a code, but generally has not given me a hard fault causing a warning. I might see this 2-3 times a year. My bet would be with the IAC motor. But being it is not an active fault it may just be sticking, and need cleaning. It is mounted above the bell housing on the back of the motor that has a hose that runs forward to the throttle body. you can remove the IAC by removing the 2 hex head screws, not the bolts. Then unplug the electrical connector. You do not need to remove the hose, it stays attached to the mounting boss for the IAC motor. Once removed you can verify it with an ohm meter. You should get about 10 ohms. Good luck, let us know what you find.

Re: Trouble with 496 HO!
 

Island Hopper,
Thanks for the info and will try in the am.

Re: Trouble with 496 HO!
 

Island Hopper,
Pulled the IAC out this morning at its only reading 0.7 ohms. Are you sure that its suppose to be around 10 ohms. My service manual doesn't say anything technical on the sensors.
Thanks!

Re: Trouble with 496 HO!
 

Also check the exhaust temprature sensors. I had one go bad on one of my 496HO's and it put the motor in the limp home mode. Replaced the sensor and the problem went away. Less than $50.00 to repair and a lost day of boating priceless.

Keith

Re: Trouble with 496 HO!
 

Kr1276, i had the same problem with one of mine on my old boat....

Re: Trouble with 496 HO!
 

Alli,
The information for the sensors is in the PCM 555 manual #33. It lists allot of the sensors, and what the resistance readings should be. The regular 496HO service manual is probably the weekest manual, Merc. has put out to date, especially regarding the smatcraft system. I guess that is why they have an additional one. I just checked again, 10.1 + or - 2% ohms is what is stated in the manual. When I checked my old one it read .9 ohms, and a new one fixed the problem. So I think you are on the right track.

Re: Trouble with 496 HO!
 

Had problem like that end up being a bad low drive oil sensor.replaced the oil jug with new sensor and since then no buzzer except the rev limiter.operator error.

Re: Trouble with 496 HO!
 

Any Luck?

Re: Trouble with 496 HO!
 

Island Hopper,
You the man, for now! Swapped the IAC this morning and no problems running on the hose. Will lake test it on Saturday. Thanks for the help and will update this weekend. Appreciate the help!

Re: Trouble with 496 HO!
 

Sounds good, let us know after you run it.

Re: Trouble with 496 HO!
 

The IAC fixed the problem. Thanks Island Hopper!

Re: Trouble with 496 HO!
 

Glad it worked out.

Re: Trouble with 496 HO!
 

sounds like you know something about 496 mags. heres my issue. twin 496 28ft pantera port has a pop at low rpm. ddt shows nothing , pop seems to go away after 12-1500rpm. shows both motors running within 50 rpm at w.o.t. problem is a sob any ideas???every test imaginable done to no avail compression.leakdown. how about injector problem???

Re: Trouble with 496 HO!
 

Badddog:

On the 496's we have seen some weak injectors that for some reason have a weak operation at idle up to about 1500rpm, then the fuel pressure increases enough to overcome the sticky or weak injector and the motor seems to smooth out, only to start popping again below 1500rpm. First thing to check is fuel pressure. Put a fuel pressure guage on the schraeder valve on the injector fuel rail, disconnect and plug the small rubber vacume line that runs from on top of the intake manifold down to the cool fuel pump system Turn the key on and read fuel pressure, it should be at least 39 to 40 psi. Start the motor and the fuel pressure should be a minimum of 42 to 43 psi. If the pressure is moderatly lower it could be a bad regulator on the cool fuel system cooler. The lower fuel pressure will not generally set a code on the scanner, but the engine just won't run right. If the pressure checks ok, you should probably suspect a bad or weak injector. With the scan tool you can actually fire each injector seperatly and listen for the injector operation with the engine not running, but the key on. The only other item we have encountered with a slight miss at lower rpms has been a bad crankshaft position sensor or sometimes a bad IAC motor, however these usually set codes for themselves on the scanner. Hope these findings help in your search.
Raylar