Mercruiser Block Drain Plugs

[flystrong]

Can anybody help me?
I recently winterized my boat and on removing the 2 block drain plugs (petcocks?) they were found to be broken and the complete assemblys had to removed. I have searched to no avail for replacement part numbers/suppliers. The other problem is i am in england and would need any prospective supplier to be willing to post the items here.
The engine in question is a 5.7 V8 Mercruiser and as far as i am aware the Serial No is OD501645 and model No 4-57B100DS.
Many Thanks.

 

[Haut Medoc]

Re: Mercruiser Block Drain Plugs

Welcome to iboats.....
I cannot help you with the specific parts, but a simple brass plug with the correct thread is all you really need.....
I'd wager you could find them in a large hardware, auto or plumbing supply......
Fyi, there is more to winterizing than just removing those two plugs, with regard to freeze damage prevention........​

 

[flystrong]

Re: Mercruiser Block Drain Plugs

That is my last option if i cannot find a replacement part. Will take the old plugs to work to find the thread sizes.
I drained the engine as per the service manual i.e. removing thermostat hoses etc. I do count myself lucky that we don't get winters like you in the States!
The coldest i have registered this winter is -4C & 1.5C in the bilge of the boat!

 

[Haut Medoc]

Re: Mercruiser Block Drain Plugs

We get the same kind of weather in Seattle, but it will dip down enough for damage......
If ya did it by the manual, good on ya!.....​

 

[Don S]

Re: Mercruiser Block Drain Plugs

Trust me, your -4C is cold enough to break blocks, manifolds, coolers, etc. So don't think for a minute it doesn't get cold enough to do damage.
Now for your plugs. For that model number, Merc shows a bushing and a pipe plug as OEM equipment.
Not sure why the bushing when all it would take is a 1/4NPT brass pipe plug to do the job, but they do bush it down to 1/8NPT.
Now, if you have the blue plugs with the orings, that's another thing. But not for that model engine. If you do have the blue plugs, let me know and I can get you a Mercruiser PN for the parts.

 

[flystrong]

Re: Mercruiser Block Drain Plugs

The plugs i removed were brass. The thread looked to be around 1/2 inch diameter but im not sure about the pitch, will check that tomorrow. Am i right in thinking that these drains should stay screwed into the block and the middle of them screws out? Mine were so badly damaged i cannot tell.

 

[Don S]

Re: Mercruiser Block Drain Plugs

Just get a brass, 1/4"NPT Hex pipe plug. Remove the bushing and install the pipe plug.
General Motors (Manufacturer of the engine) put 1/4" pipe threads in ALL the 5.7's they have made. Mercury Marine complicates it with special plugs and bushings.