Mercruiser 496 MAG Refresh Thread

[AShipShow]

Hi to all the Merc experts out there... I'm in the process of giving my new-to-me 496 MAG (0W358880) a good once over since I have it out of my boat. I figured instead of creating a bunch of new posts whenever I come across something, I'd just start a general thread that I can ask the questions in.

So far I've checked compression and leakdown and everything seems peachy there. I've also dealt with some corrosion on the oil pan by sodablasting and repainting. Next was the seawater pump which had some serious internal grooving so i replaced it with the Hardin Marine stainless pump. Also threw a new starter on as the old one was very corroded and initially needed some percussive maintenance to get it to turn over. I've also inspected the exhaust manifolds with a boroscope and did an acetone test and all looks well there. At this point I'm reassembling everything I removed to do the work above.

My initial question at this point seems like a basic one but want the experts opinion.
I went to put the flywheel back on yesterday and noticed the dowel pin was missing.
I'm 99.9% sure it wasn't there when I removed the flywheel so I looked at the merc parts diagram and sure enough there is one listed. So my initial gut instinct was just get the replacement and put it in, but then I was second guessing myself on if the motor was possibly rebuilt at some point and balanced with the flywheel in a different orientation... Not sure what the likelihood of that is and honestly would like to meet the guy that would have balanced it with the flywheel in a different orientation. I assume I'm overthinking it and should just buy the dowel and reinstall it, but wouldn't mind a second or third opinion.
Side note: if I reinstall, do I need the merc one or will any GM 8.1L dowel work? Anything special about it?

Thanks

 

[Scott Danforth]

the 8.1 is internally balanced. just align the non-tapped hole with the locating hole in the flywheel.

 

[AShipShow]

the 8.1 is internally balanced. just align the non-tapped hole with the locating hole in the flywheel.

OK, so no worries over like shear forces on the bolts or anything? I'm assuming not simply because from what I can tell, the dowel pin is a spring pin anyways, not solid, so it couldn't really provide much rotational resistance anyways.

 

[AShipShow]

Back again with more confusion... I'm an idiot and removed my power steering pulley with a 3 jaw puller before finding out that thats a terrible idea and you need to use the PS puller that you can rent from autozone/etc.. So after reinstalling the pulley and checking my alignment, I realized the pulley was now bent and has a decent wobble to it..
I went to search the part and I'm getting conflicting info... it seems like its either no longer available or a special order item...
This is one of the Saginaw Type 2 pumps and the older ones had 19mm shafts and the new ones are 17mm shafts.. The confusing thing is, my serial number should be the "newer" style, but my bore size is 19mm (the older style)... I'm having a hell of a time finding the right pulley... The only thing I've found that looks like an option is the hardin marine billet pulley kit, but thats $190 dollars.. lol

Just curious if anyone else has run into this issue with this PS pump. I was hoping the pulley would be an easy to find $30 part but of course its not.

 

[Scott Danforth]

go to NAPA, talk to the pot-bellied grey haired guy behind the counter. should be about $20 for a stamped steel PS pully.

you can also straighten yours out with three blocks of wood and an arbor press

 

[AShipShow]

go to NAPA, talk to the pot-bellied grey haired guy behind the counter. should be about $20 for a stamped steel PS pully.

you can also straighten yours out with three blocks of wood and an arbor press

I'll have to give the pot-belly route a shot...

I don't think the arbor press route will work because its not warped like a potato chip, its more that the angle of the bore of the pulley no longer perpendicular to the plane of the pulley. If it put i on a flat table, there aren't any raised areas... I almost thought about putting a 3/4" steel shaft in the bore and clamping the pulley to my workbench and trying to bend the bore back into alignment..

If none of that works, I already threw my wallet at the computer monitor and ordered the hardin marine billet pulley out of frustration.

 

[Scott Danforth]

put in a 3/4" bolt and straighten the bore.