MC-1 Exhaust Flapper.

[JimEd B]

Greetings,

I've got my 3.0 in the garage this winter, just finished a total rebuild and wanting to be ready to roll come Halibut season. This has been a year long project, so forgive the mess in the bilge. Just getting things done as I can, and I haven't been back inside the boat since I yanked the motor out. Its getting Fresh Paint as soon as it warms up, so I can't figure giving it much love until then.

I'm looking at pulling off the lower two exhaust elbows, giving them a tidy up with a wire brush and some paint or Por-15. They are rusty, and I'd imagine the exhaust flapper inside there is just about as bad as every other piece of rubber on the engine. I'd really hate to suck saltwater into my brand new engine because I overlooked a cheap piece of plastic.

The out drive is a Pre-Alpha, MC-1 which always presents parts problems. But its a good leg, and it works fine, so I don't feel compelled to swap it out until I eventually need to replace the transom.

I'm wondering if anyone can help me ID the part number for the exhaust flapper and gasket where the lower pipe bolts up to the outdrive for an MC-1? Can a guy still find these?

Here is a picture of from Ebay of the same style bottom exhaust pipe, to make sure I've described the part correctly. Also attached some other pics of the exhaust pipe in the boat for good measure, but you can't clearly see the attachment point.

 

[JimEd B]

I have looked through the stickies section on Flappers, and searched the forum, I'm just not seeing anything definitive about this particular exhaust setup. I'm sure its there, apologies for redundancy. I replaced the riser elbow last year with a new Manifold, and didn't see any flapper in the top section.

In fact, I'm not even sure where the flapper should be. Anyone care to tell me?

I labeled the potential connections for you convenience!

 

[Bondo]

Ayuh,..... Never seen a down-pipe like that, some sorta custom cob job,..??......

Usually it's a one piece aluminum cast pipe,.....

 

[JimEd B]

I couldn't tell you for sure, this is the one and only mercruiser I've worked on, but I'd guess that to be the case.

Its a Mercruiser 3.0 LX engine with an MC-1 outdrive, in a 1973 Glasply 19.5 so I'm guessing that required a bit of creativity? Last owner was a...."mechanic".... who used things like household wire nuts in place of butt terminals. Trying to track down everything he touched currently.

Exhaust worked fine last summer the three times I took this boat out last summer (mostly to see what all needed fixin'), dumped the water and exhaust gasses outside of the boat which is about all a guy could ask for really.

Is there another option I might consder to replace the whole thing?

I believe the J pipe is part No. 53113. It looks to me like the top of that pipe assembly has some sort of bracket which maybe is related to the exhaust flapper?

 

[achris]

Ayuh,..... Never seen a down-pipe like that, some sorta custom cob job,..??......

Usually it's a one piece aluminum cast pipe,.....

...Its a Mercruiser 3.0 LX engine with an MC-1 outdrive, in a 1973 Glasply 19.5 so I'm guessing that required a bit of creativity? .

And there's the answer...

The 3.0LX engine has an offset exhaust elbow, and the correct exhaust downpipe for that transom plate doesn't line up with the elbow outlet...

So yes, someone has been 'creative'....

Chris...

 

[JimEd B]

And there's the answer...

The 3.0LX engine has an offset exhaust elbow, and the correct exhaust downpipe for that transom plate doesn't line up with the elbow outlet...

So yes, someone has been 'creative'....

Chris...

I was just coming to that conclusion myself. Just my luck that last season when I was in a hustle to see the thing float, I replaced the old riser with a brand spankin' new one when I put on a new manifold..... matched to what was on the motor of course.

That's a very expensive crab pot weight.

My internet sleuthing has led to the following conclusion:

Setting it back to stock will be both easier and faster than polishing a turd. 7 bolts and 4 hose clamps easy.

Looking like I can get myself a new riser of the old boxy style (sierra 18-1972), and swap back to the one piece tube (Mercruiser 72082)? Looks like either riser will bolt up to the manifold?

Looks like the flapper is dangled in there with a bracket, anyone got the secret sauce on that? (I'd bet some merc tech paid his mortgage replacing those 1978, but he forgot to leave me the instructions here in 2022. Not rocket science but, pointers would be accepted graciously.)

How about the gasket, o ring, or whatever lives down where she bolts up to the gimbal housing? Anybody got a part number on that, or at least know what I'm looking for.