fwiw here is one answer from an intelligent source...
Q:
what would cause the bendix gear on a 2001 johnson ocean pro 115hp outboard motor to drop off after 2 seconds
On a
2001 Johnson Ocean Pro 115, if the Bendix gear comes up normally, cranks the engine for about
2 seconds, then suddenly drops off while you are still holding the key in START, I would look at a few things—but one is particularly common.
Most likely: the engine is briefly firing
The Bendix is an
inertia-drive. If the engine momentarily fires and accelerates even briefly, the flywheel can overrun the starter and force the Bendix back down. This is normal Bendix behavior. A very similar Ocean Pro case describes the Bendix dropping out just as the engine begins to fire.
So if yours does:
START → cranks strongly → ~2 sec → Bendix drops → starter spins freely
I'd first determine whether the engine is actually
trying to fire at that instant.
But if it does it with NO ignition possible...
This is important. If you disconnect the ignition so the engine
cannot possibly fire, and it still drops out after exactly ~2 seconds, then I'd suspect:
- Weak battery / excessive voltage drop
- Poor battery-to-engine ground
- Bad positive battery cable or connection
- Starter drawing excessive current
- Sticky/worn Bendix drive
- Starter shaft/helix contaminated or damaged
There is a documented case on a Johnson where the Bendix dropped after about two seconds even with the plugs disconnected; the eventual investigation showed the problem occurred only when the starter was under the load of engine compression.
Also, a 1996 115 Ocean Pro had intermittent Bendix engagement caused by a
sticky Bendix, which was freed up with lubrication.
A very useful test
Since you work with scopes/meters, I'd do this:
Put a voltmeter directly across the starter motor terminals and watch it while cranking.
- Battery sitting: ~12.6 V
- Cranking: ideally well above 10 V
- If it plunges substantially lower just before the Bendix drops, investigate battery/cables/starter.
Then repeat with the
spark plugs removed.
If it cranks continuously with the plugs out but drops out after 2 seconds with the plugs installed, that's a big clue toward
starter torque/current/compression-related trouble, rather than the ignition switch.
And don't overlook the Bendix itself: it should move freely up and down its helical shaft. It should
not be gummy or sticky.
