Detroit Diesel Starter set-up

The better marine solenoids will have 2 wires to enable them and not use a frame ground.
Your fault example is a main reason for this.
You may consider upgrading these in your future.

Also, pending the install requirements, the block is NOT tied to battery negative but floating.
Starter, alternator, shut-down, oil and temp senders will have their own negative leads.
Please check this out also; where does that negative battery lead (not bonding straps) go on the engine??

Appears back in 68 Battery Neg went to the Block

Interesting.
So there is No negative strap on the starter
or
a negative strap from the starter to the block.
or
a simple self grounding starter like on a typical Chevy car engine.

Next,
When was the last time these 53s ran?
Have they been turned over by hand and bar or spun with the starters?

I recall the negative went to the starter and jumped to the block as well.

You are correct and IMO the preferred setup.
Our new poster stated to the block.

Yeah, there is no advantage to going to the block and allowing the bolts to be your conductor.

Lots of the big Delco starters that were used (not all), were ground isolated. The negative cable had to connect to the starter.
When block ground was desired, an extra strap was from the starter to the engine block or a terminal block.
I have worked on Cats (same starters) with this same install set-up.

On my 32v Bertram, my 12V71s are floating and not tied to battery negative. Alternators have their own negative post also.
On the Hatt I work on, OMG, yellow and green 4/0 cables are all over the blocks, starters and DCv breaker boxes. Nothing floating there.

Hello mjkrawczy
You spinning/running yet?

Sorry for late response.
Negative Cable from Starter goes to the Block.
Same as a strap

You running yet? Got the water skis out?
You go first..

Not Yet.
Still cannot get Starboard to Turn over.
Voltages are correct. Pulling Starter now to check it

Pulled Starter and it Spins.
Taking it to a shop tomorrow for a load test.
If that passes I will reinstall Starter, run jumper cables directly to Starter and see if engine turns over.
This will eliminate all Boat wiring.
If it still does not turn over…..
Will see if I can manually turn it with a Breaker Bar and Pipe.
If still no joy it’s time to pull a few injectors and see if it’s Hydro locked. Worst case and I hope not.

No one in area can test my starter for a Load. Too Big.
So I swapped Starters and Starter is good.
Pulling Injectors tomorrow and see if it Rotates.

hoping no fluid in Cylinders

Agree on the Injectors being a project.
Whats the easiest way to Rotate the Detroit manually?
Unless I pull the starter again and use the Ring Gear with a pry bar.

was told not to use the Bolt in Front of the Engine.

Don't mess up the ring gear with a pry bar.
I don't believe there was a service port or turning tool on the 53s.
Use the bolt in front of the engine. The big (15/16"?) crankshaft hex head.
The manual will say not to turn to the left and loosen the bolt.

After leaning on a long pull bar for a few seconds, reality may set in.
The design of the Detroit 2-stroke in a marine environment, not running for a long time, usually does not work out to well.
Plus, no telling what issues it had when the previous, previous (previous?) owners walked off the boat.
If the piston is set in any one lung, even if you could soak it and free it, it will still be damaged and dangerous to run.
This applies to the other engine that turns also.

Next hard question: How are you going to get those engines out of the boat?
Answer; In pieces, out the back door.

Took a Break from the Boat yesterday.
Fresh set of Eyes today.
Thanks for the advise. Keep you posted

Both Engines worked fine 2 years ago. Thinking it’s a bad Ground somewhere.
Todays plan of attach is to hand over hand the Wiring on Both Engines. Hoping for resolution before the Sun sets today.
I just went through the entire Bottom and replaced all the Cotton and Slick Seam on every Plank.
Did not expect an Engine issue.
Thanks again for the advise.

Headed to the Marina now
Have a Great day