Looking for help with Cummins 6CTA (8.3 liter medium duty diesel)

[Skillet]

Engine is going into a friend's boat, supposed to launch him on Monday.  New engine from Cummins (factory recon), that was test run at their Tennessee facility.  He's doing a diesel-electric hybrid pilot project, pretty interesting stuff if you want to check it out (https://alaskapublic.org/news/environment/2025-12-23/were-really-breaking-new-ground-hybrid-fishing-boat-prepares-for-maiden-voyage-in-sitka). 

The crux of the matter is when we went to fire up the engine, the bendix gear slammed into the ring gear on the flywheel and wouldn't engage.  Based on the marks left behind, it appears this starter is not compatible with the ring gear (ring gear too "tall" to mate with the starter bendix, or the bendix gear is too large of a diameter)?  Cummins NW has said that they "sometimes" use a crank-nose starting tool to test run the engine before all the accessories like the starter, alternator, engine guards, raw water cooling systems, etc., are installed.  So there is a chance that the incorrect starter was installed after the test run...

Curious if anybody here knows these engines inside and out (or knows a pro that could identify and sell me the correct starter and fly it up tomorrow).  We have an SAE 3 bellhousing and flywheel, 159 tooth ring gear.  The starter is (I believe) a delco-remy 39MT.  It has a 12 tooth bendix gear on it, but I think we need an 11 tooth to reduce the OD of the bendix gear and get it to engage the ring gear?

So how about it folks - any of you medium-duty diesel engine guru's, or know of one in a truck parts shop I could talk to?

Thanks in advance-

Chris

[Fastass350]

I ran into the opposite when I put the last motor in my dump truck, it’s a big cam, 855. The bell housing I had took a small ring gear/flywheel setup so I had to change that out for the larger. Fast forward to installing a new trans with new clutch and new flywheel, they sold me a smaller diameter flywheel, when bolted up it was clear that the starter wouldn’t come close to connecting. Maybe it’s something as simple? Knowing what you’ll have to go through to change that all out I hope it is. Mine has the 39mt starter.

Good luck!

[Skillet]

Thanks for the info Chris...  I'm sure hoping it's something simple like that.  Decoupling this engine/gear combo inside the engine room is going to be low on my "that would be fun" list.

The Cummins NW rep has been getting me in touch with his guys this evening, so he's going above and beyond to make it right.  Hopefully we get to a solution soon.

[Fastass350]

I sure hope for your sake it’s something simple. Sounds like you got a good rep so that’s a huge win.
Something I just thought of, is it possible it’s the wrong rotation starter?

However it plays out keep us posted