Detroit diesel hole in the block, repairable?

No, you cannot weld cast iron. I've seen people drill and tap and screw a plate over a hole in Detroit Diesels before......I would NEVER do this. Who knows, I'd suspect that everything is bad......overheating wouldn't throw a rod, that's usually an over-revving situation or just run WOT all of the time, or lack of oil. There should be enough 12v71's around you should be able to find a good one to rebuild.

Could be a sign the other engine has been abused also, just has not let go YET..

Unless the price is low enough for a repower, i d run. Who knows how long the other engine will last...

BTW, QSM11s are the replacement choice for 12V72Tis with down angle clutch.
Been dreaming about it for years.

Here Lotto, Lotto, Lotto...

I'd rather replace them with C18's. hehehe

C18s are a bit beyond 700 HP and the cost.
But if I really did win the big (BIG) Lotto, I could go Cat.

I just replaced a block on one of my 12V71TI engines with a block from Diesel Pro Power. 888-433-4735
dieselpro.com

I needed a block and my mechanic shop Jacksonville Diesel Parts, Sales and Service said these folks are trustworthy. The block was $6k including shipping and was clean, checked and ready to go. They were easy to work with.

What type of boat is it? The engine needs to come out obviously which is the only reasonable way to rebuild the hulking monster anyway.

What ever Steve says at Diesel Parts & Service Jax, is gospel.
Been doing business with them for over 25 years.
Henry ran the shop then and Steve was a round kid.
If they can't help, they will point you in the best direction.

They won't come to many little boats these days, but send the engines to them.
Complete rebuild and a real dyno test and run time/HP log.
I always enjoy visiting the shop and hearing the last engine screaming away in the run booth.

When I win the big Lotto (any day now), I'll sell my perfect 12V71TIs cheap.

Here Lotto, Lotto, Lotto...

What horsepower are the original 12V-71TI's that the OP is looking to repair/replace?

TIs usually stop at 650HP. Exotic injectors may offer a lil more.
The after market marinizers leaned to the TAs for 900+

I've seen many TI's around 735 hp.

It sounds to me like the threaded holes were installed for a cover plate because it threw a rod. The holes you're describing do not sound factory to me.

If the boat sat with minial running and service for years, you have to assume the other engine isnt going to last long but you wont know until a proper sea trial is done and that means rebuilding the other engine.

Yes, there are mounting pads on the block sides. Usually hidden by the starter, oil cooler, oil pressure block (attached to these threads) and other items.
A little raised from the cast. Not meant to accept any strength from the block, just hang junk on.

If the rod really popped, the crank can not be trusted if it's still intact at all.

It's a money hole and to avoid throwing cash at it twice, I'd replace the short block.

Must be a heck of a deal knowing one engine is scrap and the other engine, although running, has no good history.
What about the gen-set?

The 650 figures were shaft HP, around 675 - 680 flywheel with factory parasites.
There were a few attempts (non factory) to tweak some more out of them (up to 750 flywheel HP) but the base TI package just could not deliver enough air.
Instead of messing with the TI, marinizers went to the TA.
With the TA, more cool air was available cheaper than after market. Now they had room to tinker with cam timing, injectors and turbos.
These changes along with paint color, Detroit was glad to provide on the line.
Other sites (Pan-Tropic) still luved to tinker them selves.

That serial number is still so important and build history is still available from DDC.
Factory horse power, IMO, is still the best tune on any Detroit block.

My 12V71TI's produce 860hp on the dyno. The turbo's are: Part Number R5101513 and the injectors are: Part Number R5229715 (9215 Injector). My engines were originally marinized by Key Power but there were others. The engines started out typically at 650hp but were increased to 800 or 850 by using larger turbos and injectors.

FM does happen. The 921X injectors are exotic in the TIs.
Larger turbos were limited in the non-water claded models. Cool if you had water cooled turbos.
Dyno 860 would be a fat 835 hp plus at the shaft. Still an impressive beast.
Forgot to mention, the 900 hp TAs has free spooling blowers when turbo pressure over pressured them.
No room for a by-pass system like the straight 671TIBs.
Maybe Key Power used these blowers also.