I'm glad someone else said it first:D JB Weld is some
amazing chit !!!!

Cracked block
 

would always replace since there may be cracks inside you don't see. These would only show up later during a long high speed run when the sounds turned a little "funny" just before it seizes from a spun bearing when oil is milky!

Wannabe in motor city

Most machine shops that repair heads and manifolds can repair it for you. They use a powder torch that heats the surrounding area to almost a molten state and sprays a metal powder into the area to be repaired. My buddy uses his alot to repair #'s matching intake and exhaust manifold for restored classics. I saw him repair an exhaust manifold that was in 2 pieces for an Edsel, after the repair and dressing you could hardly tell anything was done.

Todd

"SCRAP IT"
I tell you this from experience. It's not worth the hassle and time. I purchased (almost stole)my first boat with a cracked block. It was a 87 OMC 5.7. Bought some cast iron welding rods, pulled the engine, took it to the shop, tried to weld it up. Allot of work for a relatively cheap block. Ended up buying a block that came out of a 94 Corvette. Keep in mind - it's nothing more than a GM block with brass freeze plugs.
Remember, if the block got cold ehough to freeze, take a good look at the intake and the exhaust manifolds. Even pressure test the exhaust manifolds. Another lesson learned the hard way!!!!!!
Good Luck!!!
Jon

Oh come on now
a 5 liter will cost you what about 35 bucks from a junk yard?
dont go that route that is just jerry rigged beyond belief
if your going to do something do it right
dont rig it
yeah the jb weld and all that BS might work but comeon
and if you sell it Ill bet 20:1 you wont even mention it and if the SOB that buys it finds it, he is going to think you are the biggest putz bastard that walked the planet too.
Christ, a 350 replacement core to be built will cost you what
1000 bucks from scratch bare block from junkyard?
do it right man, I hate seeing this BS especially from what just happened to my bud RCM255
bilge filled up with hot water
went snooping and snooping around
sure enough block looked like a horses dick taking a leak
do it right or dont do it at all
Jason

Yep I did it on a Merc 350/260. Ground it clean and beveled it into the crack. JB Welded the piss out of it. I've run it WOT all summer and no leaks.

Brian

Cast Iron can be welded, but it is tricky and you have to know the technique. I fixed a leak just about like that with a two part epoxy that GM sells over their parts counter. I used a small grinder and created a bevel on both sides of the crack. Make sure the crack is clean, clean, clean. I then put a thin layer of epoxy and let it cure totally. Then roughed it up a little, cleaned it again, and put the final layer on. Make sure it cures. I bet it will be OK. Don't rush the job.

I cant believe im reading this

No wonder boats loose so much money in the few years off the showroom floor
Cause you rig your engine with epoxy
I cant believe how many of you are saying do this!!!

are you all freakin drunk?

and what happens god forbid this guy takes your advice
right
he is running say a good 2 years with a totally rigged engine
he is out not thinking about the hooptie job you all told him to do
say he is about a 3/4 mile off shore or wherever
and it springs a leak
a BIG leak
and his bilge starts filling up with water
he does not know it just yet cause he is moving
but water starts getting higher and higher and higher in his bilge
shorts out the batteries cause the starter cables and stuff are down low, blows his electrical system out and shorts it
his bilge pump cant hold out and wont work due to short
and his **** sinks
THEN WHAT
Oh well the guys on Offshoreonly told me it would hold
I CANT BELIEVE you are all telling this dude to do this
LOOK AT THE SIZE OF THE PLATE on that thing
DUDE IT IS A 305
they are about 29.95 at any freakin junk yard

Dude, dont listen to these quacks!!!
GET A NEW BLOCK
END OF STORY
YOu want to fix the freaking thing or cause more problems for you and your friends and family and put people in a possibility of danger

Get a new freakin block
im telling you 305's are in the car market basically worthless
take your internals, swap em over into new block
and just be done with that one

You guys shock me
I cant believe you told this guy to patch it

your all freakin nuts if you do that
we need more guys in here to suport the trash it and get a new one side
Jason

A new tire for the truck is only a hundred buck and no labor. Do you replace it when its gets a hole or do you have it plugged? And you can't say that that block leaking is any more dangerous that a blow out at 80mph. Just my .02

Brian

Jayl13
Hey, tone it down a little here. You have your opinion, the rest of us have ours. I don't know who you are but I don't need you calling my a quack.
The issue here is not the cost of a junk block. There will be considerable expense in anything he does unless he repairs his existing block. Maybe he does not have a lot of money to buy a block, have it checked, machined, reassembled, and installed in the boat, plus the considerable time it takes to do all this. Obviously, when you make a repair on anything you keep your eye on it, if it does not leak after a few hours of running, chances are it won't.