Want to add that Volvo did a bit different also as for the spacer. Keep in mind they are heavily rooted in the European markets so they can do some things a bit different than Merc.

Keep in mind With Mercruiser you have to changed all the BS to newer apps including the reluctor, timing chain, timing chain cover and the rest of the stuff. .

Also with Volvo you could have a 2004 boat but a 1 or 2 year older brand new engine still installed. that's why I say this engine can be boarder lined and the wrong cam sensor installed upon replacement.

you need the spacer with Volvo penta also

The oring was installed on the sensor when I got it. The one I pulled off had a small shim (0.062" thick i'm guessing) not really a spacer. But i think you might be onto something. From what I've read thru volvo's literature they changed design mid 2004. I've got the other sensor on order already (I can always return it if its not right)

It appears also that from that picture I could verify what timing cover I have by looking and seeing if the sensor input is raised or flat like in the picture. Also, can you elaborate on the spacer needed? does it come with the sensor?

What would cause the camshaft sensor to throw a code? Is the computer smart enough to know if the timing pulse isnt as expected? or is it simply a voltage thing and if theres continuity it thinks everything is ok?

Volvo calls it a spacer in their parts look up. with that said we can call it spacer shim. I have no idea what Standard has nor does Standard products actually test their sensors in a Volvo 496 to make sure it operates correctly and for years to come ?. I do know Volvo does and with the engineers. I have zip experience with Standard products and any of their actual testing for boat apps. I doubt they ever even thru a sensor in a boat to see if works, again Volvo tests all of this especially when things change from GM.

This is just one of the many reason why I do mess with online cheaper priced aftermarket china stuff. With that said if it works great for whomever but for me time is money and and the unknowing if Standard products will work in a 2004 GXI 496 Volvo s is not even worth a 1000 dollars of savings for me. - I buy what works and known to work.

I gave you the Volvo part number so until we can 1000 % verify that you have the correct spacing and the correct cam sensor installed in your engine - I am out until then. Volvo has what you need and the tech support. It might be worth the try or unless someone can prove to me 1000 % that the Standard cam sensor listed actually will work in 2004 496 GXI Volvo Penta. then we can move on. Just saying.

This cam sensor / reluctor from GM and the marine side of it has been a lunch eater for many including people who work on this stuff. When it first changed way back and those sensor were NLA but listed a newer part number with no info about it - what cluster Fukk that was.

Is the sensor magnetic, hall effect or magneto ? Can you scope the sensor with your scanner ?

Pssst: The AcDelco (read: GM) cam sensor's are typically same price as aftermarket POS sensors. And yes, I'm qualified enough to say most aftermarket anything sensors are POS's. LOL.

^^^^ Exactly and don't get me started about ebay ignition modules for a third of the price either.

Don't quote me, but i think Chevrolet has some bulletins out on the 8.1's plus other motors where the cam sensors may need shims especially if the timing cover has been removed and put back, replaced, or etc. And you can get these shims, of course, seperately.

Here is one of the 3 types of 8.1L cam sensors. ACDelco OE series for only $25.55 . Can't beat that with a stick. LOL.
http://amzn.com/B000NW6X6A

That wont work for the early 496's they are NLA but Volvo did a somethings differently.

In the pic for the cam sensor, the notch for the connector is on the wrong side for the early models as well plus the length is different FYI. I have seen 2004 & 2005 and I believe 1 2006 boats that had had the older 496 motor that uses the older NLA cam sensor. The boat manu would buy engines and let them sit until someone ordered a new boat wanting a 496 in it. Not uncommon.

Like I said this engine can be just a tad bit older than the boat year model. If so the spacer and the cam sensor that is currently installed is incorrect causing your issues - THE OLDER CAM SENSOR FOR VOLVO 3859082 I believe DOES NOT REQUIRE THE SPACER SHIM but is needed if the engine block falls under certain GM block codes in which VERY POSSIBLE your does. I am not there looking at it hence my info.. .

If your engine is a mid 2004 built then the cam sensor 3808513 is used with the CORRECT spacer shim. You have to order it thru Volvo as they have that correct. Anyways all of this NEEDS to be confirmed and the proper cam sensor and if applicable the proper spacer shim used before moving forward . I have to go get stuff done and wanted to make all of this clear beforehand. Hopefully this clears this up finally, if not we keep on truckin ahead.