Debris in lower unit

[thepauly]

Hi all,

1992 Merc 3.0LX, Alpha 1, Engine SN 0D852595, Drive SN 0D891471

I pulled the lower unit to change the impeller, and when I got the unit loose, a handful of crap fell out with it. Crap consisted of a tablespoon or two of rust flakes, and two stainless plates (see picture), as well as some gunk and nondescript crud.

What are these plates? I assume they should be attached to something, but what?

Should I be worried? What am I looking at for repair/replace? What needs further inspection?

Thanks in advance.

Background: I bought the boat about a year ago, it ran fine for most of the summer, but it overheated toward the end of the summer, 2009. I found a blown head gasket, and I'm catching up on maintenance while it's down (I haven't used the boat since then).

 

[UNSUREBOATGUY]

Re: Debris in lower unit

I'm no expert, but it's fun to give a little info I do have. The stainless plates used to be your exhaust flapper. It was covered in rubber and installed in your exhaust pipe just at the top of the pipe that exits the transom inside the boat. The rubber was melted off during the overheat and dropped off the plates. I would guess that the rust flakes were just from your manifolds or block and got trapped by the flapper plates stuck in your outdrive.

The flapper is supposed to protect your engine from water flowing back through the exhaust on a quick stop, in waves, etc. You'll want to replace it-easy to do. While you have the exhaust apart to replace the flapper, you'll want to inspect the rubber exhaust parts that connect the riser and the exhaust pipes inside the boat. Very possible they were melted/damaged by the overheat as well. If they fail-especially the bottom one, your boat may fill with water pretty fast.

Not too bad-pretty easy repairs. Good luck.

 

[thepauly]

Re: Debris in lower unit

Thanks a lot Unsure. I checked the exhaust hoses, and they seem pretty good. It looks like the original reason for overheating was the exhaust riser was clogged with rust scale. So I've got one on order along with the exhaust flapper. Thanks again.