496: Starter and flywheel teeth don't fit together tight enough
 

Hey guys. Thanks for reading this. My boat is a 2001 Formula 260 BR with a 496 Mag. I bought it used out of a saltwater environment and the boat has about 150 hours on it now. I first had to replace the starter last year because it wouldn't even attempt to turn the motor over. I think starter number one had some internal issues. Anyway, I replaced it with starter number two, a brand new Merc starter from mercruiserparts.com / BAM Marine. That starter fixed the problem and worked for a few hours. Then one time I turned the key and heard a terrible grinding noise. I put the boat up for the rest of the season. Early this year I discovered that if I turned the motor over to a slightly different flywheel position, it would start perfectly. I have run the boat about 20 hours since then with no problems up until recently. One day at the dock it got that horrible grinding noise again so I got out the socket and breaker bar to turn the motor by hand. That time though the motor would not start and would grind no matter the location of the flywheel in its rotation. I figured that it had stripped the teeth in the starter so I ordered a new one (the third starter). On saturday I spent 2.5 hours getting the new starter in only to find that it makes the same, stomach churning grinding noise that the second starter did. The second starter that I took out looks fine except that there is some grease in the bendix end with the gear. The third starter is a Merc replacement made by Mallory. I went with that brand not to save money but to see if it might be better than the Merc unit. The gear on the Mallory starter looks to be slightly smaller in diameter than the Merc starter but still, the make the same noise when on the engine.

I had thought that there must have been a bad spot on the flywheel with missing/broken teeth. When I got the second starter out on saturday I went through the whole 360 degrees of rotation on the flywheel and looked at all the teeth. They all look good and none are missing. The starter gear seems to not be meshing deeply enough with the flywheel so that when I hit the key, they just bump past each other. The weird thing is that I don't see any way of adjusting the gear lash (I'm not sure if thats the correct term). There is no adjustment built into the starters and the bolts just thread into the motor. Am I missing something there? The Merc manual says something about replacing the shims 'if your motor has them'. I don't ever remember seeing any shims. One thing is that my 496 seems to be a very early production motor. The engine serial number starts with "0M06****". Could I have gotten the wrong part from BAM Marine? We used their part number to cross over to the Mallory starter so that could explain why the new one doesn't work either.

Sorry to be so long-winded. I appreciate any help that you can give me!!!!

starter number 1 on left, number 2 on right:
http://69.24.70.63/boat/IMG5157Small.jpg


starter number 1 on left, number 2 on right:
http://69.24.70.63/boat/IMG5160Small.jpg


starter number 2 on left, number 3 on right:
http://69.24.70.63/boat/IMG5122Small.jpg


starter number 2 on left, number 3 on right:
http://69.24.70.63/boat/IMG5123Small.jpg


box from Mallory starter:
http://69.24.70.63/boat/IMG5156Small.jpg


View of flywheel teeth:
http://69.24.70.63/boat/IMG5132Small.jpg

If the adjustment you need to make is minor, you may be able to just shim it. Shims are generally used to make 'small' adjustments. If it needs more than shims, then it sounds like this starter won't work.

50-863007A1 is the OEM # and looks like you have the right item. One thing that might be preventing the bendix gear from engaging is it may be too close to the flywheel gear. This is what the shims NoQuarter is talking about. However, it doesn't look like the shims are typically used in your application - unless the original starter had shims. Did the shims drop out during the original replacement? They fit between the mounting pad on the engine and the starter housing, and could drop into the bilge.

Assuming its not a shimming problem, it must be a voltage problem. Check and recheck your engine grounds and cables going to the starter. If there is not enough voltage to spin the bendix gear fast enogh, it will not engage fully with the flywheel. Check your battery and make sure it is fully charged and has at least 12.5VDC.

Let us know what you find (if anything). Good luck!

Thank you guys for your suggestions. I really appreciate them.

What do the shims look like for a 496 application? Are they washers that go on the starter bolts? I don't think that this motor ever had them. I usually notice things like that but I guess its possible that I missed them. Are the shims used to get the starter closer to the flywheel or do they only work to pull it further away? The reason that I think that the gear mesh is to loose is the wear pattern on the flywheel in the last picture. The spots on the teeth where the rust is worn off doesn't look very deep. Also, if the starter was to close to the flywheel wouldn't the gears just spin on each other instead of making a grinding noise? I'm just trying to reason this out.....

I will check the voltage of the batteries. There are two group 27 batteries in the boat and I put the battery switch on "all" meaning both batteries. They are 1.5 years old and I keep them charged up with an onboard charger. The day before this happened, they were spinning the motor over great for very fast starts. Still I recognize that this is something to check.

Any other ideas?

They typically look like this:

http://www.volvette.com/Merchant2/gr...0001/en43a.jpg

The hole in the shim is where the starter bolt goes.

They fit between the starter and block, and pull the starter further away from the flywheel. If the starter gear is too close to the flywheel, it will not fully engage due to a tight fit. Try one pair and see what happens. If that works, look for the old shims in the bilge somewhere.

Also make sure you are using the correct starter mounting bolts that came on the engine with the knurled shafts and that they are not bent. I would also recommend getting some rust preventative and light lube on that flywheel and flywheel teeth. To much rust! Get the salt water leaks out of your bilge when running. Just some extra points here.

Best Regards,
Ray @ Raylar

Thank you guys for your help. I bought some shims the other night and I am in the process of installing them today (kind of a disjointed day...). I'll let you know what happens.

Ray thanks for your thoughts. Luckily I only run in freshwater but the previous owner did run it for 103 hours and 7 years in the salt. What type of light lube should I run on the flywheel?

Ray is right about the bolts and also if they are not tight it will not engage ...Also ....you might have voltage issues ....you need a minimum of 9.6 volts @ the starter under load ....m

Just in case the other suggestions don't solve the problem, the flywheel and bell housing may require "dialing in".

The " dialing in" is an often over looked step during assembly. However, in your case, corrosion may have caused the fasteners to loosen.
The crankshaft centerline is starting point referance. The outside starter ring radius dimension must be .005 or less when measured from crankshaft centerline. Otherwise, flywheel rotation becomes concentric, ever changing dimensions between starter teeth and flywheel. (sometimes the starter engages and other times it grinds.)

Next, the driveplate, if equipped, must be centered, to the same tolerance.

Then, the bell housing must be located to the same tolerance. (the bell housing may have moved away from the flywheel and taking the starter with it.)

A re-torqued bell housing may create temporary starter engagement, but not best solution.

A dial indicator is typically used to center all components.

There are locator dowels in the block that hold the bell housing. If either the dowels or bell housing bores are worn, it becomes nearly impossible for the bell housing bolts to hold the bell housing centered.

Unless these steps are performed, other resultants include concentric vibration, bearing side load, main seal leak and etc.

I happen to have several NEW sets of fixtures, dowels and collars for locating the bell housing to NEW.... Align honed blocks should be checked also. And, new builds.

arrover, Did you find the problem ?

Hey guys. Thanks so much for all of your help and suggestions. Friday evening I finished installing a starter shim but got the same results (grinding gear noise). Earlier this week I was reading on the Mallory Marine website to see if there were any clues to my problem. I found this tech bulletin: http://www.mallory-marine.com/pdf/Te...PMStarters.pdf . So after the shim failed to work I pulled the plugs and found water in a couple of cylinders. I'm pretty embarrassed that I didn't think to check that earlier..... Anyway, I turned the motor over by hand with the plugs out and then put them back in and fired the motor up without any problem. I idled it for a couple of minutes and then checked the oil (which looked fine). I ran the boat gently for 20-30 minutes to burn out any moisture that might have been in there and it sounded and felt fine.

So, now I just need to do some reading/research and figure out where the water is coming from. If nothing else, maybe my little hydro-locked saga will help someone else figure out their problem. Thank you guys for all the help!

Arrover - Glad you figured it out. I was going to ask if you checked that, and I assumed you did.

TAKE THE SHIMS OUT if you already haven't done so. If your motor didn't have them initially, you don't need them now.

As for water in the cylinder, it most likely is your riser gaskets. Take the risers off and look down the inside of the center exhaust ports in the manifold. If you see rust, the riser gasket failed. You might be able to just replace the gaskets and be done with it. However, if your manifolds are more than 5 years old, you might need to replace them (especially if they are raw water cooled).

If there is no water in the exhaust, your only other source is likely a blown head gasket. One thing is for certain, if water was in there once, it will definitely be in there again unless the root cause is addressed.

Good Luck!

LJ, Thanks for the recomendations. I haven't taken the risers off yet but I was thinking about ordering some new gaskets today so I could have them this weekend. I normally just order OEM Merc parts but are there better alternatives? I'm not opposed to spending a little more if it will improve my long-term reliablilty.

I THINK that the water was only in the center two cylinders and it was only on one side of the engine. Sounds like it might be the riser gaskets?

The post about the bell housing applies to Inboard engines only where the starter bolts to the bell housing.
In 16 years Mercruiser experience, I have never had to shim a factory Delco PG200 PG250 Or PG260 PMGR starter or an old 10MT starter.
Check the bolts. Check bolts for cracks.
Why did starter fail ? Why could bolts fail ?
These motors have a huge problem with reversion.
Most were not installed properly and suck water.
Many of these motors have finally let go.
We are seeing alot of them lately with water in the cylinders and rotted valve stems etc from an ongoing problem.
I suggest taking original starter apart looking for stripped stationary gear that the planetaries run inside.
Also check the overunning clutch in the starter drive in what some people mistakenly call the Bendix.
I don't recommend an aftermarket starter. It's not as good as a Delco
Clean and scrape the block. Surface it with a file.
You can also file the nose of the starter. Check that for deformaties, holes egged out etc...
I rebuild the Delco starters I install, they work great.

Get a PG 260 starter like the one that came out of it.
This should probably fix your situation.
There is also a difference in pinion teeth count 9 or 11 teeth between starters. More teeth engaged is better. S.A.E. teeth spacing is all the same on Every Mercruiser engine ! Also true the 10-12 degree bevel !
It may sound silly but the bolt length could be different, I sometimes measure the housing with a Vernier caliper when installing a different starter. I at least measure bolt protrusion. You could get a tap and tap socket and chase the block threads too. When tightening the 13MM nut on the solenoid, I use a nut driver. Don't over do it.
Great thing about these starters are that they don't use any current to energize field windings. There are none
Brushes dont burn up, almost all power is converted into torque and motion. Solenoids also almost never go bad because they get the current needed to supply the pull in and hold in windings keeping the contacts inside tight instead of arcing and heating up.

The number 1 enemy of starters is water ! looks like water got in the bellhousing and in the old starter

Cylinders with water = big trouble!
 

Water in cylinders is a very serious issue. You've got to determine where and how that water got into the cylinders in the first place. the 496 exhaust manifolds and risers are dry joint type and no water is comming in there unless the manifolds themselves are cracked and leaking. Find that water entry! If you don't and you have it happen again it could be sinonara for your engine. You should also run a compression and leak down test to make sure the water has not bent a rod from locking even with the starter turnover we have seen this and the water may have damaged the ring pack. good Luck.

Best Regards,
Ray @ Raylar

Reversion doesn't care if it's dry joint or not. Motor sucks water like a straw, especially when hot it it creates a vacuum that sucks water up exhaust. Hot motor with heat soak wants to cool off when it stops running, no longer being cooled due to latent heat temp rises. ! The way to fight this is the 1/2" per foot required deadrise in the exhaust . It uses the weight of the water to overcome this phenomenon. Some boat designers fall short, or installations arent perfect and fittings and mufflers arent positioned properly.

Also even if rings free up , pitted ring lands may lead to ring flutter and eventual broken piston rings.
Also like Raylar said, I have seen several motors with bent rods with a piston that would only come up about 3/16" less TDC than the the others .
You cannot compress water. A cylinder that is not firing properly, especially with bad valves also can enhance reversion !