Where are the drain plugs on a big block (GM) Mercruiser

[donwhiteside]

Hi- In warm California, we don't need to drain for the winter. But, I'm pulling the heads to replace gaskets and need to get the water out of the block. I can't find the drain plug (plugs??) on this 1973 Mercruiser 325 (basically a 427 GM truck engine).

Thanks!

Don

 

[Haut Medoc]

Re: Where are the drain plugs on a big block (GM) Mercruiser

I'd think there are one on each side like any GM V8 + a plug on the transmission oil cooler.....​

 

[Bondo]

Re: Where are the drain plugs on a big block (GM) Mercruiser

Ayuh,........

Down Low on each side of the Block, just above the Pan Rail..........
1 just ahead of the Starter,+ 1 just ahead of the Oil Filter......

 

[HT32BSX115]

Re: Where are the drain plugs on a big block (GM) Mercruiser

So when you say "warm" Ca. where are you talking about?

My brother lived in Novato, (warm) Ca and thoroughly cracked a 460 block and manifolds in the not too distant past!

It gets plenty cold in the San Joaquin Valley to crack a block too.

When you pull the plugs you may have poke a small screwdriver in the holes to clear the sand and rust.


Cheers,

Rick
(used to live in Warm Ca.....Now I live in Warm Wa)

Hi- In warm California, we don't need to drain for the winter. But, I'm pulling the heads to replace gaskets and need to get the water out of the block. I can't find the drain plug (plugs??) on this 1973 Mercruiser 325 (basically a 427 GM truck engine).

Thanks!

Don

 

[BAYLINER185]

Re: Where are the drain plugs on a big block (GM) Mercruiser

Your are problably just like the ones on my 7.4 ( 454)

they are brass I beleive and could be removed with a special wrench.
I dont know why they are not removable by hand like on my 4.3 engine.

I live in Phoenix AZ and it dont freeze either but it sure is damn cold now. I dont plan on using the boat as much now as I did in warmer weather but I think its a good idea still to drain the blocks water as much as possible as to prevent rust from the water standing in there.

I did drain my 4.3 and was supprised at howm much water came out. I can only imagine how much is in a 454.

 

[Bondo]

Re: Where are the drain plugs on a big block (GM) Mercruiser

they are brass I beleive and could be removed with a special wrench.
I dont know why they are not removable by hand like on my 4.3 engine.

Ayuh,..........

Nothing Special about a 9/16" End-Wrench.........

That's what All of them were before the advent of the Useless, POS, Junk, Breakable Plastic 1s of the last few years.................

 

[Don S]

Re: Where are the drain plugs on a big block (GM) Mercruiser

That's what All of them were before the advent of the Useless, POS, Junk, Breakable Plastic 1s of the last few years.................

They get 8.50 for that mess Bondo, or you have to spend 2 bucks at your local auto or hardware store for a brass hex plug.

 

[Bondo]

Re: Where are the drain plugs on a big block (GM) Mercruiser

They get 8.50 for that mess Bondo,

Ayuh,.........

Do they include the Written Guarantee that says they Break the 1st time you use'em,..??.........

 

[Don S]

Re: Where are the drain plugs on a big block (GM) Mercruiser

No, but they will sell you a new engine if you overheated and blew it up

 

[ziggy]

Re: Where are the drain plugs on a big block (GM) Mercruiser

I think its a good idea still to drain the blocks water as much as possible as to prevent rust from the water standing in there.

from my understanding. more rust occurs w/o water than with water. the damp inside w/air starts to rust. with water inside, no air, no rust..... a little rust is better than freeze damage though......