Exhaust Shutters - To Flap or Not?

[76SeaRay]

I have a used Bull Horn exhaust pipe (Y Pipe). I took the exhaust manifold couplers off the Y pipe and there were no shutters inside at the joint. This is a 1996 5.7L Vortec on an Alpha One Gen One and will be running normal height midrise elbows. Are the shutters needed or not? The parts diagram shows them but also in kind of a faded fashion which gives the impression of being optional or only used on some configurations of engine/outdrive.

 

[Rick Stephens]

 

[achris]

I have a used Bull Horn exhaust pipe (Y Pipe). I took the exhaust manifold couplers off the Y pipe and there were no shutters inside at the joint. This is a 1996 5.7L Vortec on an Alpha One Gen One and will be running normal height midrise elbows. Are the shutters needed or not?

Most definitely YES!

The parts diagram shows them but also in kind of a faded fashion which gives the impression of being optional or only used on some configurations of engine/outdrive.

Incorrect. There has been changes that may give the impression to some people that they are 'optional', but I can assure you that IS NOT the case.

This might help clear up some of the confusion...

Mercruiser V6/V8 I/O exhaust shutters explained. (only applies to 4" systems)

(EDIT: There is a parts list in last post of this thread) There seems to be a lot of confusion around exhaust shutters for SBC and V6s I/Os.. (this also applies to most BBC as well). From the start of the 'R' series and the new inner transom plate (1982), up to about 1995 the shutters used...

forums.iboats.com

Chris...

 

[76SeaRay]

Thanks for all the info. I don't know where the water line will be at since I have never floated the boat (bought it at auction needing the new transom). But, will double check it once I float it. I had read somewhere that the design of the shutters changed somewhere mid-90's but thought it was in 1998. The above would indicate it changed in 1995. That said, my engine is a 1996 but the sterndrive is earlier (MR drive) and that would be the determining factor on which shutter (early shutter) to get for it. Will need to order a pair of shutters.

 

[alldodge]

Flaps don't hurt, but if you have room put a 3 inch riser in and leave the flaps out

 

[76SeaRay]

So, confused with the shutters. The video's online show shutters that are oval in shape and a slot for some type of rubber holder to slide into the Y Pipe. Mine is round with a couple of holes in the sides of the tube. There are crumbling round rubber bushings in the holes. What shutters do I order and how do they install? Adding pictures below.

 

[alldodge]

That looks like inboard exhaust parts. You have a V drive or I/O?

 

[achris]

So, confused with the shutters. The video's online show shutters that are oval in shape and a slot for some type of rubber holder to slide into the Y Pipe. Mine is round with a couple of holes in the sides of the tube. There are crumbling round rubber bushings in the holes. What shutters do I order and how do they install? Adding pictures below.

Did you bother to read the document I linked you to? If so, all of this ^^^ is explained in that document.

Chris........

 

[achris]

That looks like inboard exhaust parts. You have a V drive or I/O?

No, that's an early style y-pipe with the 'single plate and axle' shutters. He has an Alpha One, as described in his forum signature.

Chris.....

 

[76SeaRay]

Yes, I read the link but it says it applies to 4 inch exhaust only. Mine measure 3 inches although the elbow has a larger diameter on one end. I think the larger end goes to the manifold elbow though.

Found this part so I assume it is the correct one 99370A2.

 

[76SeaRay]

Since this is an older Y Pipe (but in good condition), is there any reason I should replace it with a newer or larger diameter (4 inch) Y Pipe?

 

[alldodge]

Since this is an older Y Pipe (but in good condition), is there any reason I should replace it with a newer or larger diameter (4 inch) Y Pipe?

No
The larger ones are one size fits all 4cyl to BB 8cyl

 

[76SeaRay]

Thanks for all the info. I just ordered the shutters above so should be able to move forward as soon as they get here.