exhaust restricter or no

[Lodgepole]

Have a 1992 OMC 3.0 HO Cobra. Exhaust flapper fried and plugged exhaust in drive. Unit has gasket only where riser connects to manifold. Some exploded parts diagrams show upper and lower gasket with a restricter. What is the right answer. (flapper is almost impossible to find but I found 6)

 

[Maclin]

Re: exhaust restricter or no

If you mean a restrictor at the riser to manifold joint, in many cases that is referring to water passage block offs/restriction, you need the right set for open versus closed cooling.

 

[chiefalen]

Re: exhaust restricter or no

http://www.dougrussell.com/partscat...on=group&group=17&GroupList=17,18,19,20,21,22

Above is the site i use to look up omc stuff, not buy from. The page is for my drive and motor, go to the side bar and click on omc and pull up your year and motor and see what that site calls for your setup.

Last thought from me, i don't understand why they put a restrictor plate there, i would think they could have designed a riser that had it built in. And maybe thats what made the motor overheat, and burn out the flapper.

Previous motors don't have them with the same drive and motor but i think it was when volvo and omc joined together and volvo started making the decisions.

So there is another decision to make and only you can make it with research on your part.

Do you put the plate back on when other motors and drives didn't have it if called for by the diagrams?

I won't even go into if the flapper is needed or not, it's a hot topic here, and you can do a search and make up or own mind.

But bear in mind volvo latter did AWAY WITH THE FLAPPER.

Good luck !

 

[boys boating around]

Re: exhaust restricter or no

The Douglass Russell website is the best out there for OMC's, you can't go wrong with their diagrams.

I have a 1996 OMC 5.0 on my 19' Four Winns bow rider where I recently ran into this issue. My riser rotted out and a LARGE piece of the riser fell into the exhaust getting caught on the flapper. This caused major back pressure in the exhaust which caused the gaskets to blow out leaving me stranded in the middle of the bannana river

During my search for the flapper valve I too could not find any in stock around the country. I then found out that OMC issued a service bulletin regarding the flapper. They no longer use the flapper and stated that you could remove them if you are servicing the exhaust. Just make sure that the gaskets cover the gromett holes in the tubes or JB weld them.

The valve is meant to prevent water from returing back into the engine on a quick shut down. Sorry but I don't have the service bulletin number anymore but I'm sure that if you call them that they will have it.

Also I found this place to be the best price on risers and manifolds for OMC's.
www.marineengineparts.com

 

[Maclin]

Re: exhaust restricter or no

I believe the restriction term used to describe that gasket setup refers to the water passages. Maybe the water needs to be under more pressure to get to the top of the riser and out the exhaust or it would flood back easier during shutoff, I am not sure and that is just a guess. More likely there is a closed cooling wet/dry manifold system as well that those risers and/or manifolds are used in, and the extra passages have to be there for the closed system's plumbing and restricted for open cooloing. Could even be the reverse of that. Which one to use for your setup is what a factory manual would tell you.

 

[Lodgepole]

Re: exhaust restricter or no

I have a Volvo service buliten about no flapper necessary. I am not sure I want to run that way. When at the beach and a barge comes by, there is a lot of backwash and also with a quick shut down. Boat maintained proper temp with good impeller and thermostat and no restrictor. This would seem to allow a good amount of water to pass over flapper with the exhaust to keep it kool. I suspect a damaged impeller is what caused the flapper to fry before I got the boat. Will see what my manual shows whun I get back to OK where the boat and manual are.