Where's it go?... big plug

[Tanner]

Ok, I've never dewinterized my boat myself. The dealer temporarily winterized it while they had it. When I got the boat back from the dealer, I LUCKILY looked in my glove box to find my plugs laying in there in a baggy. I know where the exhaust manifold plugs go, and the block plug goes. But where does the big round silver circular plug go? Anybody? Pics would be ever so helpful... but I can follow a good description.

[dogbert]

What engine?

[Tanner]

06' 340 MP

Is this a knock sensor? I didn't crawl into the motor to see if I could find where it goes. Trying to save some time, as I'm running this boat to my buddy's stereo shop at 7am.

[dogbert]

I'd check around your water pump.

[chpthril]

My 06 340 has 1 plug in each exhaust manifold, 1 pipe-thread plug in the port side of block, and a knock sensor for the starboard block plug. Same threads and hole size though. Look for a single wire plug laying loose by the starboard motor mount.

[Tanner]

Thing is about the the size of a Half Dollar, maybe slightly larger. Threaded. and IF I remember right... it has a square head in the center of it.

[dogbert]

Hmm, sounds more like a freeze plug. I'd call the dealer.

[Tanner]

Looks like it might be the engine drain there in chpthril's pic, where the knock sensor plugs into. Hard to tell only going off of the brief 5 secs I looked at it.

[Tanner]

Thanks guys!

[balair]

umm...I'm pretty sure that is the drain plug for the back of the boat....the only square head plug is for the drain plug i think. just look behind you're boat just above your taps plate

[jleger98]

Looks like it might be the engine drain there in chpthril's pic, where the knock sensor plugs into. Hard to tell only going off of the brief 5 secs I looked at it.

I don't have the 340, but my engine has one of these on each side in the exhaust manifold. Threaded and a square hole in it just the right size for a socket wrench.

The other option is to put it in the water and start it and see where water comes out

[Tanner]

umm...I'm pretty sure that is the drain plug for the back of the boat....the only square head plug is for the drain plug i think. just look behind you're boat just above your taps plate

LOL... .good one. It's not the drain plug. I can honestly say that after 15 years of boating, I do know what a drain plug looks like.

[balair]

ok i was worried there haha...i have never seen a square head on anything else tho..i have the same engine too

[Tanner]

It might not of been square... I honestly can't remember and I'm locked out of my storage after 10. I'm about 95% sure that it's the Engine drain as labeled on Chp's pic. The "square part" I saw, is probably where the wire attaches for the knock sensor. My memory is probably fried... it's probably not even square at all....lol. We'll know tomorrow morn.

Part of the reason I'm so sure is I've never known where the starboard size plug was. Only the port side and exhaust manifolds.

[dogbert]

Yeah, seems like Mercruiser likes to put a bunch of stuff around the knock sensor so you can rip up your knuckles in the process of removing the drain plug.