Look what I found in my exhaust tube!!

So I remove the drive to replace the bellows (which look like new, soft without holes) and find this!








Is this the flapper thingy that broke off? I did notice my port riser is much warmer than starboard. What should I do about this?

thanks

Re: Look what I found in my exhaust tube!!

That's half of an exhaust flapper. Time to replace them flappers.

Re: Look what I found in my exhaust tube!!

Can I put the drive back on before changing the flappers?

Also, why do I have a temperature difference (by touch) between the two risers?

Where exactly are the flappers and how is it changed.

Thanks.

Re: Look what I found in my exhaust tube!!

Yes, you can put the drive back on. Difference in heat is probably due to water flow restrictions. You may ALSO have a plugged riser. That piece of flapper is a significant restriction. I'll bet that once you get them replaced, you'll notice a big difference in power.

Since I have NO IDEA what boat you're working on, I can't tell you where the flappers are. Since you mentioned 2 different manifolds, I feel it's safe to assume you've got a V-8 or V-6.

If you're lucky, and have a newer exhaust system, the flappers will be at the top of the Y-Pipe, just below the risers.

If you're unlucky like myself, and have an older boat, the flappers will be at the base of the Y-Pipe, where each side bolts to the transom plate. There are 3 Allen Bolts on each pipe, which will have to come out. You MAY be able to get them loose without removing the engine, provided you've got some nice long Allen Sockets, and plenty of room to get into the bilge. If not, you'll have to pull the engine.

Either way, the risers are gonna have to come off, so you might as well check the top of the Y-Pipe first.

Do you have the proper manual for your boat?

Re: Look what I found in my exhaust tube!!

Just noticed the boat in your signature, if that's the one we're talking about, I THINK you'll have the flappers at the top of the pipe.

Good luck.

Re: Look what I found in my exhaust tube!!

Thanks for the info. it's a 5.7 350 V-8 vortec. 65 bucks less in my wallet and a trip to the nearest merc parts shop, I picked up the flappers for port and starboard. According to the merc manual, looks like I just need to remove the elbow.

It didn't say anything about removing the manifolds.

So far my drive shaft & shift bellows looked like new. I get to return those parts. I don't have an exhaust bellows just a tube. Anything I should check on it?

Placed new gasket and rubber o rings where applicable and the drive is back on. Tomorrow I'll replace the the water impeller, housing and related pieces.

Thanks again.

Luis.

Re: Look what I found in my exhaust tube!!

Don't take off the manifolds! Just unbolt the RISERS from the manifolds, and set them to the side. Remove the rubber boot that connects the risers/down pipe, and the flappers should be right at the top of the pipe. Swap 'em out, replace the boots. Reinstall the risers with new gaskets, and go enjoy some time on the water.

Careful not to drop anything down the pipe, or you may be pulling your drive back off, to get it outta there.

I also recommend putting a rag in each exhaust riser opening, so nothing falls down the exhaust, and into the head!

Re: Look what I found in my exhaust tube!!

Risers have to come off.But now you get a chance to inspect them see if they are still good.

Good luck!

Re: Look what I found in my exhaust tube!!

Yeah, good point. Check the risers for blockage and excessive rust/flaking while you've got 'em off.

Re: Look what I found in my exhaust tube!!

I'm afraid of the inspection. I'd hate to drop another 450 into this engine before getting it on the water. Dam.... Hopefully the previous owner flushed after every dunk.

Guess I need to get the gaskets now. Seems I've taken 3 trips to the hole in wall parts place. I hate this place, very unprofessional. I normally purchase stuff online much cheaper, but for the sake of being able to return parts quickly if not needed or if it's wrong, local is nicer (with a price premium).

Re: Look what I found in my exhaust tube!!

This is neither here nor there, but...

I made my own gaskets out of fel-pro rubberized gasket material from Autozone. Total cost was $6, with enough material to make 20 sets of riser gaskets...

Dealer wanted $17 per set, and 2 weeks to order 'em.

Re: Look what I found in my exhaust tube!!

Nice tip!!! I really appreciate that tip!

Hopefully the old gasket comes off in one piece, or in large enough pieces that I can trace out onto the blank gasket. If not, I can probably put some oil or ink onto riser and stamp the blank gasket to trace and cut. THANKS!!!

Re: Look what I found in my exhaust tube!!

The gaskets use a metal plate between the riser and manifold, sandwiched between 2 gaskets.

Just use the metal plate to trace it out. The plate will have a small vent hole on the fore side of the manifold. Just make sure you have an opening in the gasket for that vent hole, and you're golden.

If somehow your plate has water jacket openings to allow the water to flow from the manifolds, into the elbows/risers, then you will have to cut the openings for those jackets as well.

A good sharp hobby knife will be a good thing to have. I used a drywall knife, and it worked, but an x-acto knife would have been a lot easier.

My manual actually has templates for the gaskets, but my boat has the older "log" style manifolds.

Re: Look what I found in my exhaust tube!!

lmannyr said:

...Hopefully the old gasket comes off in one piece,....

Click to expand...

Good luck with that. I had to remove the risors on my '76 888 unit to replace the hardened and pinholed boots. I have never experienced any thing as glued on as they were. I think they must have used liquid iron to cement them in place. As far as I could tell, they were the original risors and gaskets. It was a low hour freshwater boat so the old risors were still in good shape.

Re: Look what I found in my exhaust tube!!

Removing the risers was a non event. made some gaskets out of felpro from autozone and reused the metal gaskets as well. All the passages looked black only. I was very happy to see no build up, rust, or flakes.

The port shutters were still there but with not much spring to them (replaced with new). The starboard did not have the second half shutter! I only found one piece as mentioned earlier.

Is it possible the other half blew out of the exhaust sometime or could it be stuck in the Y-Pipe? I would really hate to take out the Y-Pipe!!! Any suggestions?

Thanks!!!!