Busted Block

I do know from this forum that the Ford EFI engines do not allow any upgrades without causing tuning issues.   The GM Throttle body design, I don't know in Marine Applications but I suspect it may not be so restrictive as the Ford unit.   
In Automotive applications, GM Trucks with the Throttle body injection I was involved with a few hundred that converted from 350 or 305 to 383 engines.   We also has some Mild cam changes and the Throttle body always adjusted just fine.
Some chose large camshafts and for those we had to bring in a friend who was a GM trained tuner and he could fix them.   For a Stock Camshaft I suspect the throttle body would work fine with an upgrade to a 350 but my thoughts are not any type guarantee.   You should poll the forum to see if others have done this upgrade.   I suspect you will find many more users of the 305 engine in other Forums, Bayliner, Sea-swirl and many Outdrive boats ran the Mercury Marine 305 as a base engine.   I did have a friend switch his 305 in a bayliner to a 383 and that thing was scary fast but he has moved and I lost touch, I don't know what mods he did if any to make it run with the larger engine. Check first before abandoning the idea of using a 350. It may be a simple program change or it may be impossible, please share what you learn.
You also have the option of switching back to a carburetor, a good carburetor still works pretty well and allows you to use any engine you choose.
Mark

I have installed 350 vortec engines in Silverado trucks that came with the 305 and as long as you use the stock vortec 350 camshaft we never had any tuning problems . If you are working with a budget going to a carb will most likely add $1000 dollars to you repair if you think about a new carb intake fuel pump wiring changes etc it would add up quick at a dealership charging you $ 90 to 125 labor an hour . You would never get those cost back should you ever sell your boat plus most people would want the EFI should you sell the boat. I would like to hear what the dealer quote is . If your motor has low hours a block swap could be done using all parts from your motor on a different block. If money is no problem a new 350 is your best bet . If your where in NC I would stich - lock your motor and not even remove to motor from the boat.

1TAZZ wrote: I have installed 350 vortec engines in Silverado trucks

Joe,
Any marine engine experience? PCM?

Reading all this, would this be a fair summary?

Easiest, lowest cost fix - replace the 305 block with same, use all your parts, hit the water. No additional power.

Higher power fix - replace with a carbed 350. You lose efi but gain power without breaking the bank.

Utopia fix - replace with crate engine complete. Very expensive, all the power your choose to spend on.

PCM ought to be able to tell you if you can swap out a 305 for a 350, and what will be involved with the efi, if anything. 5.7's don't cost much more than a 305 and are a better engine. Maybe you'll get lucky and it'll be an easy swap.

I’d be inclined to drain the water from the block, grind a groove in the crack and fill it with jb weld. Have seen some lousy external repairs hold surprisingly well. If the leaks are internal, the block is toast. I wouldn’t spend a dime on pulling the engine and trying to stitch a 305 block together.

Also good luck trying to get specific 350 vs 305 efi tune info from pcm on a 20 year old engine. Maybe worth asking but don’t expect much of an answer.

If it were me, I’d drop a Vortec longblock in there and maybe give the efi system a chance- being super vigilant about looking for signs it’s running lean. If it can’t be easily addressed, I’d carb swap it.

Or look into bobtail options, would expect them to be in the $10k range with labor.

63 Skier wrote: Serious question for Tazz and others. Say you try the stitch, it works for a bit, then starts weeping or even a small steady stream. Would that matter? I'm not saying leave it that way forever, but if the block is leaking warm water at a rate of a gallon an hour, what harm would that do? Just curious.

It wouldn't matter to me.

That's what JB weld or Marinetex or __________________ fill in the blank with your favorite epoxy is for.

As far as TRB's JB weld fix............now we're getting into my territory, a good ol' backyard hack job   Count me in

Kinda hard to see in the original pictures if it's just a crack or if the water jacket is pushed outwards on both sides and needs to be pounded back to shape first( and maybe break in the process)

GLP Post better pictures

GLP

Click on the link below for a little reading on an epoxy patch here on CCF   

link   

This is close to me.
https://youngstown.craigslist.org/pts/d/chevrolet-305-v8-engine/7076136042.html

And this one
https://youngstown.craigslist.org/pts/d/youngstown-84-camaro-engine-and-drive/7093824091.html

I like the idea of a used engine. How would the transmission work? Do I have to worry about it linking up appropriately since I have the direct drive? Or are they universal?

TRBenj wrote: Or look into bobtail options, would expect them to be in the $10k range with labor.

Tim, what is the most likely bobtail for easy fit and match for the boat? Just curious.

I don't remember how good this engine was before the freeze wrecked it.   If it was a good running engine a Short Block would save some money. Buy a Head Set for gaskets and install your old heads and other parts.   Just another Idea to get you up and running.
Rebuilt Short blocks are not a lot of money and lucky for you pretty easy to come by.