sonic prowler 496HO PCM PROBELM??
 

I have a 04 sonic prowler with the 496 HO I have been experiencing the batteries draining over night and now the last time it was taken out it ran fine for about 25 mins then the rpms dropped back toaround 4500 and at idle it would almost cut off then come back like the key was turned off and back on really quick. Has anyone experienced this problem or know what to do. I am thinking it is a PCM problem but wanted to know if there was any testing to make sure before buying one.

are you turning off the perko switch to isolate the batteries, Im assuming you have one

Is it beeping?

If you have a bad plug wire that arcs spark to the block before the plug it affects the pcm running the motor.

the only way the batteries will not draw is if i turn them off through the switch. it did start beeping a couple times a minute and when its cuts out and comes back it beeps like it does when you turn the key on.

You need to have it scanned. If you plan on keeping the boat for a while, buy your own Rinda scanner. Do a search here on OSO on "Rinda" and you will find details. It's the best money you will spend on that boat, longterm.

It's likely a bad IAC, very common on these motors, but can't be certain without a scan.

Always turn your battery switch off. It's not like a car with a frame, and an elaborate ground system. Anything could be drawing the battery down; but it's likely your depth finder and stereo, in that order.

yes i was looking into purchasing the software as i have already had to have a friend scan it for me and i usually make a habbit of turning the batteries off but if i do forget they will be dead in 4-5 hours so it is relatively quick

how old are the batteries, sounds like one or both may have issues, and if the charging system cant keep up with current draw your ecm may be warning of low voltage, JMO

What I want to know is have you been switching the perko to battery 1 to battery 2 or to battery all when the boat is running ? If so never ever do this.

Next load test your batteries - and a good battery is 12.7 volts not 12 volts. Once they drain completely dead over time, it really weakens the cells in them internally. Very hard to have solid battery voltage after that takes place so many times. What is your battery voltage when the engine is running ?

Also check for all connections to the batteries / and perko switch for tightness and no corrosion. Also check backside of engine grounds they need to be clean and tight. Also connections at the starter need to clean and tight. Then scan your motor and report what fault codes have / are showing up.

POST # 4 Jersey Outlaw is correct about the spark plug wires as if it is arcing especially at idle the engine will seem to stall and restart itself. Also bad IAC can really effect idle and off idle acceleration. IAC's have been a huge problem for Mercruiser engines over the years.

What type of warning horn / beeping do have ? Solid or 2 beeps every minute or intermittent continuous beeps. They all mean something different and can lead you to the problem area.

i always turn the batteries to both when i turn them on. the batteries are about 7 years old and i wouldnt mind replacing them if the draw wasnt so quick its almost like the key has been left on. the charging system charges at around 13 at idle and around 14 when cruising. i was getting two beeps a min and if i tried running it wide open it became solid. i will be ordering the diacom software monday so i scan it.

7 year old batteries no doubt YOU NEED BATTERIES. Your lucky they have not stranded you. ECM/ PCM controlled engines need steady and the correct voltage to receive the proper inputs from the 5 v and 12 v reference sensors and signals to command the proper outputs from the computer. It all starts with battery voltage as soon as you turn the key on.

Also I was asking if you change your perko selector switch while the engine is running not after the engine is shut down or before start up. I understand turning the perko switch off when your done using the boat.

Also is your stereo hard wired straight to the battery still drawing power/ amps when the perko switch is turned off. See this a lot and the batteries going dead weeks later after the boat sits .

7 yrs ?
WOW !!!!

BTW: A dead/shorted cell battery will pull a 'good' battery down with it when they are connected.

I suggest using 'all' only for jumping a battery.

2 beeps every minute could be IAC - 4 sure. Solid beep at full throttle could be overheat and or exhaust manifold temp overheat. This also could be throwing the engine into limited power reduction mode. (guardian mode) from 5 % to 90 % available power depending on what the problem is.

Also solid beep can be overspeed / (over reving) bumping off the rev limiter. Hence this also can put the engine into 90 % available power mode or less. You need batteries 4 sure before you do anything else even for scanning the engine. Good luck

ok i will start with some batteries and a scanner and see where that gets me. I never turn the perko switch while the engine is running. The stereo does not work with the batteries off and isnt wired to them either. When i bought the boat the previous owner stated that they would draw down quick if the batteries werent turned off and that he had replaced the batteries seveal times so the batteries drawing has been an on going problem for years. one thing i did forget to mention is last time i had it scanned the crank sensor was reading -112 which is a misreading for sure but the boat ran fine for several months after. Im not sure if the pcm could be drawing these batteries down or something else.

An interesting thing with newer FI motors. It takes much less current to crank them as the small gear reducted starters are quite efficient, but much more current to run and support the electronics. An older carb motor really only needs enough current to run the module and the coil.

The point here is that you may never even here a change in cranking speed but the batteries are not even close to being up to snuff. Battery test is step one, checking terminals for tightness and cleaning step 2. Until you are sure the base electrical system is valid, I wouldn't get too crazy about what is causing the alarm to go off. Once you are sure your batteries are up to snuff you can move on to the alarms and battery draw.

And I had a battery go 12 years on my Regal. I was so amazed after 8 years that I decided to see just how long it would make it. It's easy to take that chance with 3 batteries and a push button parallel switch. When it did quit, it crapped out all at once with no warning.

Yeah I agree I definitely need to get a set of new batteries then go from there. I'd say 7years is a long time for a set of cheap autozone batteries the previous owner put in