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Does anyone have any good recommendations for where to find one of these. My block cracked in the recent cold freeze.

If I were replacing that motor, I would consider replacing with a 350 depending on if your current motor is carbed or fuel injected. If it's carbed, easy peasy. With fuel injection, more work to get it converted.

What year is your motor? Makes a difference sometimes because of the interface to the drive if its a one or two piece rear seal.

Also, WAY easier finding 350s

Michign Motorz is one place. https://www.michiganmotorz.com/

My engine is 1983 model so not sure , has anyone had any luck trying to weld it back together

Welding cast is tough. Preheat/postheat, prep, etc. Not to mention access to get to the crack. Check your local shops to see if you can find one interested.

I'm not speaking from any real sense of authority of confirmed knowledge here, but I was thinking, why not just use a Chevy Truck long block (or even short block if you are capable) and bolt on your marine components. After my preliminary thought, I did some digging and found this thread - https://forums.iboats.com/threads/diffe ... ck.170603/

I would say with the lower level of investment in your boat, that just might be your best - including from value - solution.

Also - There is a rebuilt (remanufactured) 305 Mercruiser Long Block on EBay right now for $3600 (as well as a few used complete engines)

andymoler58 wrote: Mon Feb 20, 2023 7:39 pm My engine is 1983 model so not sure , has anyone had any luck trying to weld it back together

You need an engine with a 2 piece rear main seal.

DEcosse wrote: Tue Feb 21, 2023 1:14 am I'm not speaking from any real sense of authority of confirmed knowledge here, but I was thinking, why not just use a Chevy Truck long block (or even short block if you are capable) and bolt on your marine components. After my preliminary thought, I did some digging and found this thread - https://forums.iboats.com/threads/diffe ... ck.170603/

I would say with the lower level of investment in your boat, that just might be your best - including from value - solution.

Also - There is a rebuilt (remanufactured) 305 Mercruiser Long Block on EBay right now for $3600 (as well as a few used complete engines)

The problem is, he is going to have to find a truck block 1986 or older because of his 2 piece rear seal. Even if he finds one, it will have to be rebuilt. Best to just buy a rebuilt block.

bruceb58 wrote: Wed Feb 22, 2023 1:17 am The problem is, he is going to have to find a truck block 1986 or older because of his 2 piece rear seal. Even if he finds one, it will have to be rebuilt. Best to just buy a rebuilt block.

Well sure, that's what I'm saying - just that he should consider a Truck Block vs a "mercruiser' one (although there are also 'marine' rebuilt long blocks on Ebay also, but most I've looked at with that designation are 'reverse')
I didn't look closely enough at the Mercruiser one I referenced above, yes that one is single seal but main point I was making was actually to consider truck engine

Maybe this - https://www.ebay.com/itm/251091488821?h ... Swc6pZ8iUH

I have no personal experience of that particular re-builder but they do have warranty and also some configurable extras if desired and reasonably priced

Or these guys - https://www.ebay.com/itm/264436283426? - much better warranty (3 yrs) and much better feedback rating

DEcosse wrote: Wed Feb 22, 2023 12:58 pm

bruceb58 wrote: Wed Feb 22, 2023 1:17 am The problem is, he is going to have to find a truck block 1986 or older because of his 2 piece rear seal. Even if he finds one, it will have to be rebuilt. Best to just buy a rebuilt block.

Well sure, that's what I'm saying - just that he should consider a Truck Block vs a "mercruiser' one (although there are also 'marine' rebuilt long blocks on Ebay also, but most I've looked at with that designation are 'reverse')
I didn't look closely enough at the Mercruiser one I referenced above, yes that one is single seal but main point I was making was actually to consider truck engine

Like I said, you will have to find a truck engine from a truck 1986 or older. Such a truck won't have 50K on the engine, and if it does, it will have been sitting around 30 + years and will have to be rebuilt anyway.

You don't have to buy a "mercruiser" engine...any rebuilt 305 or 350 will be fine as long as it's a two piece rear main seal.

An engine out of a truck would have to have it's heads removed at minimum to have the metal head gasket replaced and you would have to replace all the core plugs.

Better to buy a rebuilt motor.

bruceb58 wrote: Wed Feb 22, 2023 1:33 pm Better to buy a rebuilt motor.

I'm not saying anything different - never suggested anywhere that he buy a used truck engine

DEcosse wrote: Wed Feb 22, 2023 3:41 pm

bruceb58 wrote: Wed Feb 22, 2023 1:33 pm Better to buy a rebuilt motor.

I'm not saying anything different - never suggested anywhere that he buy a used truck engine

Well there is no such thing as a Mercruiser 305 or 350 block since Mercruiser doesn't make 305 or 350 blocks.

If he buys a rebuilt "truck block", as you keep on saying, he has to change out the head gaskets, water pump and casting plugs.

You don't mention what boat that is in, only reason I ask is because if this is more of a project boat then I might gamble with a used or rebuilt motor from an unknown source. If this is your relatively new "I use it boat" that justifies a little more $$, then I would personally look for a long block (assuming your manifolds, and other components are good and you can either install it yourself or have someone who can) from a reputable rebuilder like Michigan Motorz or Jasper. The other option is to drop in a crate motor which should be ready to run, but of course there is a cost involved - if you get to this point MerCruiser sells rebuilt replacement engines.

Also, check your insurance, it could be covered.

Good point on insurance check with them. On my old boat my out drive blew and was getting ready to pay for the repairs and someone recommended to check with insurance. To my pleasant surprise it was covered minus deductible !

There are plenty of these Mercruiser engines listed on Facebook marketplace. Around 1979, Cobalt switched from the 302 and 351 cu in motors, which were Ford based, to 305 and 350 cu in motors, which are GM based.

These GM based Mercruiser motors are readily available out there. Don’t know where the OP is located or uses FB…. But dozens are out on the market.