OMC round plastic disk pulled out of exhaust bellows

[i_build]

I was preping my drive for paint today when i stuck my finger in one of the holes on the bottom of the exhaust bellows because i saw something loose in there. It looked like it might have been an oyster shell or large clump of barnicles that grew inside of the exhaust bellows and was not attached to anything just free to move around inside the bellows. It was too big to pull through one of the holes at the bottom of the bellows so I cut from one hole to the next and it removed it.

It looks to be a round plastic disk that appears to have had a sealant or adhesive around the perimeter but it was in bad shape.

I looked through these diagrams http://www.sterndrive.info/omc_help_page.html
but cant see a plastic disk used in the exhaust line anywhere. Anyone have any idea what this thing is? Looks like something slapped together for some reason.

Thanks in advance.

 

[Don S]

Re: OMC round plastic disk pulled out of exhaust bellows

Could be an exhaust shutter. Care to give us some more information, like what OMC outdrive and engine you may have?, and year?

 

[Bondo]

Re: OMC round plastic disk pulled out of exhaust bellows

Anyone have any idea what this thing is?

Ayuh,...

It sounds like maybe a Flapper Valve...

 

[i_build]

Re: OMC round plastic disk pulled out of exhaust bellows

I am sorry. It is a Cobra and GM 5.0. Can it be run without it?

Drive is an 1989 and engine was replaced in 2000.

 

[Don S]

Re: OMC round plastic disk pulled out of exhaust bellows

Can you run without it, Yes. Is it recommended, NO.
Your choice.

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[i_build]

Re: OMC round plastic disk pulled out of exhaust bellows

Sure looks like it. Is it a big job to replace? Maybe I will find a link for someone that has done it. I was hoping to be in the water next week. Man what a downer.

 

[Don S]

Re: OMC round plastic disk pulled out of exhaust bellows

Yea, that's it. They look like that from overheat (lack of water) which causes the exhaust gasses to burn up the rubber parts. And those looke burned.
I would suspect that the inside of the exhaust hoses look about the same, and may blow out.
Pull the risers and check to see if the water passages are all plugged up. If not, when was the last time the impeller in the outdrive was replaced.

 

[i_build]

Re: OMC round plastic disk pulled out of exhaust bellows

I just bought the boat and have been running it on the flush muffs and it has kept cool. I will check as you recommended and report back. Thanks... better to do it right now and postpone than to rush and regret it latter.

 

[Don S]

Re: OMC round plastic disk pulled out of exhaust bellows

Running on muffs in the driveway has no load on anything. If it's new to you, then you better be checking things out before heading to the water.
Check the impeller, pull the drive and check for water in the bellows, check for water in the fuel filter, check the drives gear lube, and pull the risers and replace the shutters and check the manifolds and risers for plugged passages.
Then you will be close to heading for the water with your new (TO YOU) boat.

There is actually a lot more stuff to check, but you get the idea.

 

[i_build]

Re: OMC round plastic disk pulled out of exhaust bellows

I did the drive lube and it wasnt milky. Ran it on the muffs for a while and drained and refilled with fresh lube again.

Changed out the fuel filter / water seperator.

Changed oil and filter.

Cleaned carb

Put new plugs in (back 2 were fouled pretty bad but all others fair... dont know why???)

Adjusted the shift linkage and brought the idle down to 650 from 800.

Changed the dizzy cap. Points and wires look good.

BUT.... I found that flapper today. Read some posts saying they arent needed and volvo stopped using them... but read some more posts about being hydro locked when you dont have them and stop abruptly....

Thanks I appreciate the help.

 

[Gary H NC]

Re: OMC round plastic disk pulled out of exhaust bellows

Idle should be set in the water in gear...You will find now that 650 will be too low once the boats in the water with back pressure and a load on the engine.

To replace the missing flapper the engine needs pulled.Most people run without them. Its there to keep water from pushing back up the exhaust if you stop fast or take a wake against the stern.

You should really do a test run in the water before changing a bunch of stuff.

As Don stated,the drive needs to be pulled,u-joints,gimbal bearing and seals inspected.

 

[Don S]

Re: OMC round plastic disk pulled out of exhaust bellows

To replace the missing flapper the engine needs pulled.Most people run without them. Its there to keep water from pushing back up the exhaust if you stop fast or take a wake against the stern.

Hold on there Gary, the flappers are at the top of the Y pipe. It's a Cobra outdrive. Look at the parts diagram I posted earlier.

 

[i_build]

Re: OMC round plastic disk pulled out of exhaust bellows

Good point on the idle I will adjust back up and finalize in the water.

I did read a few posts on how to change the omc cobra flapper and it did not require pulling the engine and is apparently simple. I will be pulling the risers first thing a.m. tomorow to inspect them.

As far as pulling the drive, I know how to pull the drive, but am concerned because I dont have an alignment tool to put it back on. Is the alignment tool a must?

 

[Don S]

Re: OMC round plastic disk pulled out of exhaust bellows

As far as pulling the drive, I know how to pull the drive, but am concerned because I dont have an alignment tool to put it back on. Is the alignment tool a must?

Yes it is, unless you enjoy pulling the engine to replace a $300 coupler. The alignment bars can be found on ebay for 50 to 75 bucks all the time, or, if you have a lathe you can make one easily.
But the alignment should be checked at least yearly, and any time the drive is off. Which also should be at least yearly.

 

[chiefalen]

Re: OMC round plastic disk pulled out of exhaust bellows

Yes. E-bay has them under 50 bucks delivered.

You don't know what changed in all these years the motor and drive were installed.

Check the bearing while your at it.

Check everything.

 

[i_build]

Re: OMC round plastic disk pulled out of exhaust bellows

Thanks Guys....

Starting to feel like I felt when I built my first turbo rotary engine. Time to read read study and read some more then empty my bank account.

New pump kit, alignment tool, bellows (since I'm pulling the drive) and who knows what else... but I'm glad because I was overlooking these things and that flapper and you guys opened my eyes. Thanks again.

 

[Gary H NC]

Re: OMC round plastic disk pulled out of exhaust bellows

Hold on there Gary, the flappers are at the top of the Y pipe. It's a Cobra outdrive. Look at the parts diagram I posted earlier.

aaahhh....Sorry Don..for some reason i was thinking bottom of the Y pipe...

Been awhile since working on my old Cobra...

 

[i_build]

Re: OMC round plastic disk pulled out of exhaust bellows

UPDATE

I pulled the risers and hoses and guess what.... both flaps were there.

I looked through the original owners paperwork and he put in a new long block in 2000 but the mechanics notes on the prior engine was that there was water in the old engine.

So in theory that burnt flapper could have been the cause of the prior engine dieing and could have been stuck somewhere in the Y pipe only to be blown out into the exhaust bellows after the new engine was installed (my theory).

The risers look to be another story though. I have a shot attached. Are these risers toast? It's my first I/O and I'm not sure what looks good or not or even how to clean them.

 

[Don S]

Re: OMC round plastic disk pulled out of exhaust bellows

That riser looks fine to me, not all plugged up. Clean the gasket surface and be sure to check it for flatness and they should be good for a few more years, even in salt water if you keep them flushed after use.
They probably did replace the flappers, too bad the mechanic didn't have enough sense to look for the old ones, they do get stuck in the Y pipe, the bellows and even in the drive itself.

 

[Bondo]

Re: OMC round plastic disk pulled out of exhaust bellows

Ayuh,..

This was a junk Alpha I picked up a few years ago,...

No wonder the Crabber that owned thought it was Down on power, just before it Blew Up....

It's a pretty common thing, anytime after a Lack of Water Flow situation occurrs...
Everybody changes their Impeller,+ Never look at their Exhaust...