Yamaha 4.3L Stern Drive - Freeze plugs and Exhaust cracked

[Fletch2018]

Hey, can you please help me. I was stupid and didn't drain all the water out before winter. So 3 freeze plugs blew out, and it looks like one exhaust manifold has a small crack at the bottom of it.
Where do I get new freeze plugs from? Do they have to be specific to Yamaha stern drive? I have no clue.
I am also going to take off the exhaust manifold and have a machine shop weld it and fix it. (or put some JB Weld or waterproof silicone that withstands the heat).
Then I will put it all back together and see if any leaks. What do you think?

 

[Scott Danforth]

welcome aboard

your core plugs come from your local automotive machine shop for a GM 4.3

your exhaust manifolds will be difficult to get, however you will need to get new ones. do not try to repair. there is a thread on here for converting to the mercruiser manifolds

you will need to pressure test your block and heads after you install core plugs to see if you cracked the block. most likely you cracked the block and will be looking for a new motor. if that is the case, get a complete mercruiser setup from carb to prop and replace your obsolete and busted yamaha stuff.

 

[Fletch2018]

Thank you Scott. That is what I feared. But the thing is that when I start it up, it runs very good despite all the water everywhere. I only ran it a short time. Oil still looks good too. I thought if the block is cracked then the engine would not run, but would fizzle out, and the oil would be look milky?

 

[Scott Danforth]

Motors run fine for a short time without coolant and busted blocks

 

[Bondo]

Ayuh,.... Welcome Aboard,.... As Scott says, a cracked block can run perfectly, but still be junk,.....

Standard Chevy brass core plugs can be bought in most parts houses, some ya may have to order 'em,....
I believe you'll find they're 1, 5/8",....

 

[Fletch2018]

Thank you Bondo. I am trying to find some brass ones now. I will hammer them in and then take it to the lake to see if the oil level on dipstick rises after running it for a good while. Thanks again everyone for your help.