496 CID Mercuriser won't start

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We have a 2000 model 496 CID 375HP Mercursier sterndrive in a 26 foot Formula boat. The 496 won't start. It seems to be starter flywheel related. It runs great when it starts. We put on a new marine starter and it worked for a while and then when it would not start we could turn over the engine a little with a wrench and then it would start. Then later it would not start at all. Put on another new marine starter and nothing at all. It just sounds like the starter is grinding against the flywheel. We were able to turn the engine over 360 degrees and there does not seem to be any flywheel teeth missing. Any thoughts? Thanks a lot.
 
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So it is not the ignition or fuel system, but it simply won't crank/turn over? Maybe the starter has to be shimmed, like many old GM starters. If turning it by hand a bit helped, then it sure seems like the mating is questionable.
 
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So when it does not start, the starter is running but not turning over the engine? Please expand on what happens when it does not start.
 
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Examine the teeth on the bendix closely. Are they being chewed up? Does it look like it's catching the flywheel in the wrong spot? If you can, look in the hole where the starter goes. See anything wrong in there? This is a big block Chevy engine; is the shim pack correct for the starter? Bendix could be binding with the flywheel(to close) and chewing up the bendix that way. I had a similar problem in a big block Ford some years ago; a couple of teeth in the flywheel were bent just enough to chew up the bendix every year or two.
 
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The problem has to be orientation/alignment or the flywheel. The odds are way too fat (or slim for that matter) at getting two defective starts for replacements.
 

callbay

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The engine will not turn over. It ran and started the day before. The boat has two batteries that are 1.5 years old and I keep them charged with an onboard charger. When it doesn't start, the starter turns over fast but makes a terrible grinding noise (starter bendix grinding against the flywheel?). I have looked at all of the teeth on the flywheel and they look good and none are missing. I doubt that it is a bendix since two starters do the same thing. The teeth on the bendix don't look chewed up. There is some metallic powder around the bendix area of the starter but not much at all. The Merc service manual says to reinstall the shims if the motor is equipped with them. I have never seen any shims on this motor and none came with the new starter. The 496 starters do not have any adjustability built into them. The starter bolts go through holes in the starter and thread into the engine. It seems to me that shims would only serve to move the starter further away from the flywheel and I'm not sure thats what needs to happen. Thanks for all your help.
 
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Are you also using the bracket that goes on the end of the starter that faces toward the front of the engine? Lots of guys throw it away, but it's very important. It keeps the starter from flexing away and wrecking the bendix and ring gear.
 
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il
 Originally Posted By: callbay
The engine will not turn over. It ran and started the day before. The boat has two batteries that are 1.5 years old and I keep them charged with an onboard charger. When it doesn't start, the starter turns over fast but makes a terrible grinding noise (starter bendix grinding against the flywheel?). I have looked at all of the teeth on the flywheel and they look good and none are missing. I doubt that it is a bendix since two starters do the same thing. The teeth on the bendix don't look chewed up. There is some metallic powder around the bendix area of the starter but not much at all. The Merc service manual says to reinstall the shims if the motor is equipped with them. I have never seen any shims on this motor and none came with the new starter. The 496 starters do not have any adjustability built into them. The starter bolts go through holes in the starter and thread into the engine. It seems to me that shims would only serve to move the starter further away from the flywheel and I'm not sure thats what needs to happen. Thanks for all your help.
So can it be shimmed or not? Can you get a picture? I believe it you put a shim under just the outside bolt mount, it'll rotate the starter closer to the flywheel.
 
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Ur starter is incorrectly shimmed When u get a replacment starter sometimes u have to shim them even thou the original one wasnt shimmed
 
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