Starter won't disengage

[Jasonlocke]

Hi there, I have read a few forum posts on this and tried a few things but still have the same issue. I have a 92 bayliner bowrider with a 3.0 mercruiser inboard. I recently had my starter rebuilt, and after reinstalling it, it ran great for one or two runs. Now, when I turn the key to start, the starter winds up and won't turn off without disconnecting the battery. I pulled the starter out, connected it to a battery with jumper cables, and jumped the two posts to get the starter to engage. It works fine when connected straight to a battery on the bench (disengages when I remove the jump). So I put the starter back in and reconnected everything. Went to start it, same thing, won't disengage. Removed exciter wire from starter, tried jumping it, same thing, won't disengage (without disconnecting battery). Removed all wires going to starter except for line from positive on battery. Same thing, won't disengage. I even disconnected the wiring harness in case there's a short somewhere. I'm not sure what to try next... any ideas?

[jimbunyard]

Likely an alignment or shimming issue. You might try not tightening the starter quite so much, but be careful, too loose can cause chipped ring gear teeth. If loosening works you might be able to make a shim out of some shim stock metal...or auto supply stores usually have them. Could also be a faulty solenoid, but that the starter works on the bench makes this less likely.

[dlymn]

My guess is mechanical; the starter cog and ring gear are jamming. Check the cog on the starter. You might find slight wear for most of it and then a very small ridge on each tooth. Past use has allowed the starter and ring gear to wear into a comfortable fit. Changes to bearings and shaft position now means that the little ridgesare engaging with the ring gear and jamming. If the starter doesn't have a solenoid then the wear could be on the fly-in thread
You might try some emery paper to smooth the ridge. Regular use will eventually recreate a comfortable fit. Shimming the starter out from the bell housing might help.

[Cheechako]

Not sure about the 3.0, but on a 5.0 I owned I discovered different # of teeth on some starter gears and flywheels. I wonder if the rebuilder got the wrong # of teeth on there? Apparently a 9 tooth or 10 tooth will actually work, but if not matching can cause wear.
Is yours a drive actuated by a solenoid to thrust it out or by centrifugal force?

[akkebeng]

I "finished" no less than three starters in rapid succession before finding the fault. The ignition key stuck in the starter position because of a mechanical problem so the bendix was held engaged by the solenoid instead of jumping out once the engine was running. The starter obviously was not rated for 30000r/min, at least not continously, and the commutator in the starter fragmented after five to ten minutes causing a magnificent short so in the next tenth of a second, the cable from the solenoid to the engine burned off like some 1000A fuse.


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[GordMay]

Greetings and welcome aboard the CF, Jason.

[Teknishn]

akkenbeng beat me to it....faulty starter switch. In troubleshooting it helps to find the common denominator. The start solenoid obviously works, as does the starter. You pulled the starter out and bench tested it and it worked. What was the one thing that you didn't pull out and test....i.e. the starter switch and associated wiring.

Oh the joys of working on boats. The most complicated problems tend to have the simplest of solutions

[Jasonlocke]

Thanks for the tips guys. So I tried loosening the starter. This particular starter is fastened with two bolts, a short and a long. I connected the positive from the battery only. I jumped the starter to engage it, and same thing, it started and wouldn't disengage, made a grinding sound as usual. I wiggled the starter away from the flywheel and it disengaged. So I am under the assumption that the starter gear needs to come completely out to disengage properly after it is engaged, does that sound right? And it seems like it isn't coming all the way out right now when fastened tightly in place. There were no shims when mounted prior to the rebuild. I checked the flywheel gear, it doesn't seem to show any signs of damage or excessive wear. I can turn the motor by hand. The gear on the starter looks a little rough, but not bad. Would filing the gears on the starter help it engage properly? And thanks again for the help and warm welcome to the forum.

[hellosailor]

My own experience has been that a lot of the guys who rebuild starters and alternators are just plain slobs. Since it was just rebuilt, and "installation" usually is just a really simple "bolt it up" process, I'd suspect the rebuild was cheating. There's a starter throw-out mechanism (usually called a "Bendix" because that company invented the classic one) and when you engage the starter, it physically moves a solenoid and pushes the starter motor to engage the drive teeth. When you let go of the key, that mechanism is de-powered and in theory a simple spring pulls the motor back out. In practice? A bent part, or some old congealed grease, or a stray metal shaving, are all it takes to prevent disengagement. I even had a 6 month old "new" car starter fail that way once, just plain defective. I'd suggest unbolting it, going back to the rebuild shop, and saying "Takee Fixee" to them. And if possible, take a peek at the shop workbench. If it isn't clean enough to eat lunch there? Yeah, they're slobs and you can't trust the work.

[jimbunyard]

Generally speaking the high torque, light weight starter (gear reduction) uses a 11 tooth pinion, the direct drive, heavy weight, normal (?) torque starter has a 9 tooth pinion. They are supposed to be interchangeable.


The pinions are hardened, I would try and stay away from grinding them unless it was at last resort. From your response it sounds like it is a clearance issue of some sort. As a test you could put thin flat washers on the bolts between the starter and the block tighten normally and see if it solves the problem. If it does, you need to shim the starter. This doesn't tell you what happened, but it gets you back on the water. Most likely there's a loose tolerance somewhere in the parts that were replaced in the rebuild. Who knows?