OMC Cobra Volvo Penta SX Exhaust Seal Flapper Damaged/Stuck 

Thanks, this helped me understand what the rubbery cap / flap looking thing was underneath the stern drive where the exhaust comes out. Turns out the flap broke off and got pushed down and was blocking the outlet! Cheers man!

If the exhaust hoses are really stuck on you can try spraying silicone spray up in the joint between the hose and pipe, and CAREFULLY use a hair dryer to heat the rubber just a bit to help it expand and come off. They can get really stuck on.

Hey Michael, my exhaust flapper melted and made it all the way down to the sterndrive. What a bummer. I'll tag you in the video . Thanks for all of your videos. -Randy

That is the result of a past bad overheat. The melted part is probably in the lowest part of the exhaust housing and may not be reach-able unless you pull the outdrive. OMC used them till the end of their run but Volvo discontinued them as per their service bulletin. I think they discontinued them in '99 or so. I do think flappers are good to have, due to the risk of water coming up the Y pipe, they are not hard to replace.

Useful enough for me.. mine was completely off and i did not know which side to face up! Thanks!

If you do not find any exhaust lappers they are most likely downstream and blocking hot exhaust water.

Appreciate the video. I posted this last night on a forum for help. I ran across your video. Not sure if stuck flapper is part of my engine miss but sounds like I can do without it. I run in an East texas lake and have done away with my thermostat already. Think the flapper could be causing the engine miss? Engine miss and new rattle developed in exhaust manifold: 91 OMC King Cobra, 5.7LE Chevy Just rebuilt carb, and reinstalled, changed fuel water separator. Motor started on first bump and bench settings were perfect. It idled as smooth, as good as it ever has. Measured 15-16 inches Hg vacuum and needle rock steady. Took it out for test drive and ran great. Opened it up to 4000 RPM @ 45-50 mph. Was ready for a great weekend. Wait for it... Couple hours later, daughter wanted to go out, as soon as I started to throttled up, I could feel Engine miss and got progressively worse with more throttle. Engine sputtered and popped. I turned around Immediately. Did the following checks. Fuel Pressure ~ 5 psi Base timing 8 -10 BTDC per manual Checked Distributor and rotor. Noticed significant green corrosion all way around inside cap. I touched up all contacts with sand paper, shined up the rotor. Pulled plugs, dry. A couple had some light carbon but I’ve seen them worse before rebuilding carb. Double checked gap @ 35 degrees. To no avail, engine miss still there and I noticed a new noise. Sounded like a faint rattle. I thought it may have been rocker arm or something worse deep in the engine, but after listening more closely, I think it’s coming from the port side exhaust manifold. I read through the cooling system section in the manual thinking there might be some sort of flapper in there. I thought perhaps it might be contributing to the engine miss some.

Michael! AGAIN, awesome video!!!! Come fix my gd boat! I'll buy you a super burrito!

An easier way to do it, spray the grommets with silicone spray, then buy a spare pin and use it to drive the old pin out part way then pull it out with a vicegrips.

Found mine in the lower unit housing the shift selector rod caught them, the pins were in the bottom of the exhaust y pipe

What if you look and all that is there is the metal pin? Lol thats all i had in mine. No flap. Have no clue where it went.

Hello, nice videos. I was just wondering if you know about the service bulletin that volvo penta issued years ago stating not to use them. They say they are not effective in preventing water ingestion and fall apart and clog the exhaust system.

Great video (without engine) to show what this is all about. We had a water pump go bad and an overheat (happens fast, sand is tough on little impeller) on a VP 4.3 SX. A year after repair and ready for first run of season the left side riser and exhaust were running 100 degrees hotter that the right. An obvious water block somewhere and I suspected the flapper thing. After taking apart the elbow and rubber I see the flapper is not there. Gone. Only the axle pin remained. So i had a skinny guy with long arms reach in all the way to bottom and he can’t find it. The pipe is clear. So where did it go? Melted away? Curious as what to do next? Anything? The obstruction was found in the hoses and thermostat housing. Suggestions?

Do you think if this is damaged, it could cause water to be getting into the engine and mixing with the oil?

Nice job..very informative

Micheal, I am pretty new to the OMC System. I have an 1989 4.3L V6 GM. Engine is running fine when not engage. I can run the engine up to 4000RPM and so on without issue. When the boat is engage in forward and start moving I cannot reach more then 2500RPM and you can feel the engine loading. I have looked your videos about the ESA System and also how to change the shift cable and now this one... I am bit lost and i would like to have you thought ? Thanks

Hey mike is this a must to have fixed ? I only operate on fresh waters . But I recently overheated my right manifold and I’m sure if it was made of fiberglass it got ruined. It runs fine with. No weird noises. Mehta do you think?

Did you expropriation any loss of power? My volvo penta 7.4 seems to be struggling to get up on plane. I'm wondering if this may be my issue. To much exhaust restriction

Mine is broken and way down under the drive

Do you have videos on replacing the Y pipe and gaskets?

Hey Michael, just wanted to say I've watched many a video of yours of the last year and you've helped my in my rebuild. That being said I'm back here looking at this video because in my rebuild i didn't put the flappers back in per the comments on here and in other forums I've read. Today however I was heading back to the dock and my engine died. And trying to crank it again it wouldn't turn over. Turns out i water logged it. What i don't know is how, i didn't reverse it at full speed nor did I come to a full complete stop after being on plane. 2 main reasons you'd get water logged without the flappers. Now I'm considering putting them back on. Any insight? Thanks.

Do you have part number??

I bought an older bayliner with 460 King Cobra and I have been fixing all its issues. After removing my outdrive I did find the flappers clogging the bellows. Should I replace them? Or just leave it without the flappers? Didn't know how much of a risk it is for sea water to travel up through the Y pipe. thanks for your help

Wow. I just found this.

great video. im having a problem with one side of my exhaust running 20 to 30 degrees hotter than the other. could the flapper valve be stuck cause this problem thanks

Mine are intact but very stiff in operation. Can I lubricate them with something?

Hey, great video! my penta 4.3 gx overheated and the flappers are all melted to. So i'm planning to remove them, however i saw some water dripping from around the underside of the y pipe when the boat was in the water. Do you think the gasket of the y pipe is leaking to? Found some small holes in the exhaust below to. And is it possible to remove the y pipe whithout lifting the engine? Thank you in advance!

hey i know this is an old video but could this be the reason of smoke/steam coming from the transom?

So I have a 1997 4.3L GL with the sx cobra outdrive. I had a bit of an overheat in my driveway. (Earmuff fell off) pegged the temp gauge. Cooled right down after moving ear muff back into place. Thinking I may have to replace this. I'd like to put them back in. How do you get to them with the motor in(slide exhaust bello or boot down then remove pin?)And do you have a part number of a set of flapper valves that will work for me?

How many hours were on this engine when you noticed this? Thanks for the heads up!!

do you show reinstall? and where did you get them as Volvo discontinued them via service bulletin.

Omc 545 king cobra. My engine is getting really tight starter cant turn it after about 5 mins in the water. Boat was turning off when hot randomly and then I have to wait to start it. Took my risers off, no rust inside and looks solid. I notice one of my flaps is close and one is open. Would this cause engine to die and lock like im having?

you didnt show how to installit

Michael, I have a 90 Donnie levante with twin OMC’s. I just purchased in Sept. and had a month of season with it (I am in MN) before blocking it for winter. In that month the port side engine hydro locked 4 times. All 4 times the engine was at idle and shut off, then go back to re-start and motor is locked. Have to remove plugs to drain out the water before I’m able to re-start. Aside from this the engine runs strong. I am just not sure what is causin water to creep that far up the pipe and into the motor so often, and am really confused as I am stationary when it happens and not pulling the motor out of high revs or anything. I need to check the condition of the flappers this spring, but I am curious is if you know any other malfunction that could be causing a vaccume (or whatever it is) that is sucking the water into the manifolds..? Any suggestions are very appreciated.. thanks in advance.

If these are bad would it cause a exhaust fumes smell inside the boat?

Do you have a part number?

Hey man could this cause me to have bogging issues on acceleration by chance? If I slowly walk the throttle up like can hit wot but if I "gun" it like to pull a wakeboard out of the water my engine chokes and falls on its face. I've already done the fuel cell paint clean out and new filters plugs etc so I'm wondering if this could be the one thing I havent tackled. Thanks for any and all help. Love the videos

Good video!