496HO issues
 

Put a used 08 496 HO in my 99 Searay 230 last summer and it seems to be in guardian mode. Bought the bluetooth unit for scanningto see what is wrong and it powers up fine, tablet pairs up but no PCM communication. Other issue was I had to jump a ground wire on neutral switch to get it to turn over in neutral to start. Runs fine but cant get any rpm over 3500 and seems like has less power than the old Alpha 350 setup no matter what I prop it with. I have a feeling PCM is issue as the start issue I believe is lack of ground through PCM to complete circuit. Havent found proper diagram for electrical to trace properly. Would a reflash correct this? Do I need a new PCM?

Before you go blaming the PCM I would look at you scan tool, we had the genuine Mercruisers bluetooth attachment thing and it ended up in the lake...........it didn't work very well for us lol. Also the safety natural switch does not have a ground wire, it will be yellow with an orange trace, it's the starter trigger wire. The switch will be closed in natural and this switch is in your throttle/shift controller. If or when the 496 goes into guardian it will alarm and shut you down, read the DTC if none are shown read the freeze frame data, your find your answer in that. Personally I would look at your fuel system pull the fuel filter cartage from the cool fuel, under that filter there is a "pancake" style fuel filter that many people don't change and gets clogged.

before you even get started and a bunch dart throwing for answers gets posted. He the deal. 496's are app specific - meaning what and which 496 did you buy ??? 2008 at least half of the 496 s were DTS apps if not more. so did you get a DTS app ? Next is at least half 496 were installed in inboards and or even jet boat apps and even wake boats. . The PCM 555 is app specific per Inboard and or a app with a transmission or I/O and wake boats.

An engine serial number of the 496 you bought needs to be posted for exactly what what it is and set up

Being app specific with the tune in PCM 555 will automatically cause guardian at 3 K to 3500 K --- ( the set up and wrong cal in the PCM 555 for the wrong app installed.)

How did u wire up your trim wires and so forth with a 99 transom assembly ? Who's wiring harness did you use for the bought 496 ? That should be a 14 pin not a 10 pin - How many spliced wires were done for the complete install ? There should be zero. Too many unknowns here to even come close why you have guardian and many unknown installs. Alot more info is needed for any help.

Most important did you buy an 496 that was installed in an inboard app and then installed in youir I/O app ? if so that is problem number ONE. to start with.

Do you have a shift in gear switch and set up correctly for the install ?

marine apps are marine specific scan tools needed. no go for blue tooth or some internet software. or auto store scan tool will not work period.

Engine is an 08 non DTS out of stern drive. Using Mercury Vesselview with bluetooth. Had to ground the one wire to neutral to get key to start engine in neutral. Used the Mercury 10-14 pin adapter for harness. No splices. I purchased motor used and believe reason I am having issues is why it was removed. Was sold as an insurance claim due to broken starter mount which turned out to be nonissue other than removing rest of broken bolt. Rebuilt the seawater pump ( bad bearings and seals), tore fuel pump down and replaced both filters and pump. Runs and starts good at low power but no performance. Vesselview is supposed to communicate and display codes. Powers up and communicates with Android device but no pcm. Hard to find any marine guys in our area familiar with the 496.

you need a scan tool connected to the DLC - and scanned while lake tested. 4 scans needed - key on only then running at idle - then fully warmed up and one running around all rpms on the lake.

Then know what all means from the scanning. Many think just because they have a scan tool that will find the fix. I wished it was that easy. Many times no fault codes will show but many out of spec parameters are the issue.

ALSO you could have a BAD PCM. If a storm engine very possible for a BAD PCM. Make sure all your 5 V sensor circuits are showing good and not out of spec

and lets forget the people you bought from could possible be hacks. And or they installed an inboard set up 496 for an I/O that did not work for them hence why they sold it. Not uncommon. The used market is full of hacked crap from owners and cobbed jobbed shops. Actually this statement is more true than not. Even a few OSO members selling junk crap. either clueless or think their crap is worth something. I bought some stuff here and it was dumpster chit when I received it. Not even that long ago.

for starters I would and check which PCM u have by the sticker on the back.

Finally got boat out of storage. First new question, would non dts setup need anything plugged into transom harness? I plugged 1 wire in to get trim sender to work, all else seems ok. Vesselview powers up, connects to bluetooth but cant find Pcm. I still think I am missing a power wire somewhere and pcm isnt fully reading something. I have asked other places and searched the internet and cant find a proper diagramfor a non dts 2008 496 HO. Anybody able to help? Found info on an old 496 thread about shift in gear switch. I have mine grounded to get it to start in neutral but that ground may also make computer think it is always in neutral limiting power and rpm. The way I grounded it seems to make neutral switch work as it wont turn over in gear but it is a bandaid partially masking real problem, hence needing a diagram. Engine serial on cover is partially rubbed off, original transom and drive #s there(I dont have the units). Any other place to find #?

Did some more testing today and all harness checks are good but to get engine to turn over with key the 5V signal through in gear sensor needs to be grounded and after engine starts it is limited in RPM. The sensor tests ok. I am thinking PCM is issue as there is also no communication on data lines to vesselview. Analog guages all work. Some numbers on PCM are rubbed off. What is left is XR002E6V on top under bar code, PCM0701 next, build date of 01-29-2008 and then 897906 which I believe only identifies main case as that number seems to apply to alot of these units in different engines. Of the rubbed off numbers Bravo is visible so I believe it is proper sterndrive application.

Any suggestions at all? Do I need a transom harness plugged in? Is start in gear switch on engine a possible issue. I dont want to buy a computer if I don't have to. Serial number is rubbed off engine cover but numbers posted above for computer are all I have. Cant find anyone nearby with a Rinda scanner. No warning beeps unless I unplug a sensor with key on. 5V reference good at all sensors. Dont want to rely on fact vesselview not working to condemn computer either.

Serial number is 1a3100560. Found on heat exchanger. More tests. In gear switch on motor has 5V on ylw/pnk always but blk/ylw has 12v with key in crank position. If a ground is provided to blk/ylw it fires starter relay and starts and runs. 5v on ylw/pnk doesnt provide ground ever. That wire goes directly to harnessA on computer. Blk/ylw goes to start relay. I would think computer would control ground to allow cranking but why 5v on wire? Is my 10-14 adapter wrong for this engine? Is a transom harness with steering sensors and trim control necessary on this application? Few dealers and boat shops called locally have no clue. Nearest boat shops to me dont even have 555 adapter for their scan tool. Hicksville here. Anyone want to sell me a rinda with adapter? Going to run a 17 prop so I can take family out. Boat will run 30 mph like this for now. When asked what engine I say 4.3 not 496 when on water.

When you did the vessel view did you put the correct terminator on it? I had to buy one for my vessel view as it wasn't on my boat. Until I did that, it wouldn't find the PCM.

Is there more than one type? It already had one and that is where I plugged in vesselview and installed terminator on vesselview harness. Check resistance of terminator and it makes connection to join pins.

Well, what color was the one that was installed? I had a cover but not a terminator. I had to buy one. I think the "cover" was purple and the terminator I bought was yellow. I just had a similar problem to you where it wouldn't find the PCM and that was the issue. Hope that helps.

Cover is yellow and I believe it says terminator on it, but will check to make sure. Thanks for the input.

rinda scanner found
 

Scanned engine and repeated codes for pitot sender and fuel level codes, all there as it isnt wired for them. Does this 08 motor need transom harness hooked up and wired to operate properly? Need to water test with scanner still. Still cant find reason why no crank unless I ground 1 side of in gear senor unless that is affected by transom harness as well. No other codes and all pcm and static tests all pass.

Water test done
 

Went out with scanner and all tests and parameters pass. Engine is 100% power available all the time. 42lbs fuel pressure under load. Water pressure at 24 lbs. Ran the original 17 3 blade stainless the alpha setup used to run and boat ran 52 mph @4800 WOT. Seems a little wimpy for a 496 HO in a 23 foot runabout. Engine scan showed much higher hours than was told when I bought engine. 938 after today. Most below 3000 rpm. Is this engine in need of some freshening up? It runs nice and smooth, no smoke and has good compression(170psi) on all cylinders. Anything I can do to get any performance out of her as is or is it rebuild time? I have a spare running 8.1 truck motor I could build as long block to replace this one with and swap but not this summer. Is thru hull exhaust necessary with this engine and maybe that is contributing factor? Install manual I found online says not recommended to just do prop exhaust except in Europe where thru hull not legal. I have merc diverters and compressor, just need to find some side exhaust tips to install.