Riser interchangeability

TheHunter990

Seaman Apprentice
Joined
May 27, 2012
Messages
41
We need to replace the exhaust manifolds/risers on our Alpha One Gen One system. Has a V8 305 chevy for the engine. (Plan to switch to a 350 as well as exhaust). Engine serial A570518.

This 4"/7 degree outlet manifold/riser seems like it is much more available than the 3" 15 degree currently equipped.
$_12.JPG

This is what we have now (Mercury 98503 riser):
riser.jpg

2 questions:
Is it possible to use the slightly newer? 4" outlets? I can't help but notice the rubber boots behind my riser increase in size to fit on the Y pipe...

We're thinking about getting Sierra replacements, are they a quality product?
 

achris

More fish than mountain goat
Joined
May 19, 2004
Messages
27,468
Re: Riser interchangeability

You need to change the aluminium tube and the rubber boot between the Y-pipe and the elbow use the 4" outlet elbows.

Interestingly that serial number comes up as an inboard, not a sterndrive...

As for quality, I use the following list when buying manifolds and elbows...
OEM (Mercury)
OEM (Mercury)
OEM (Mercury)
OEM (Mercury)
OEM (Mercury)
OEM (Mercury)
.
.
.
.
.
Osco or Barrs
.
.
.
.
Sierra
.
.
.
GLM (Absolute last resort)

Chris..........
 

TheHunter990

Seaman Apprentice
Joined
May 27, 2012
Messages
41
Re: Riser interchangeability

I should also ask: Is it worth it to switch to the 4" elbows or would that be throwing money into the wind?
 

Bondo

Moderator
Staff member
Joined
Apr 17, 2002
Messages
70,468
Re: Riser interchangeability

I should also ask: Is it worth it to switch to the 4" elbows or would that be throwing money into the wind?

Ayuh,.... Pretty much,..... Go Boatin',... Have Fun,.... ;)

Btw,.... No matter who's risers ya buy,...
Clean both gasket surfaces, Clean,... Flat, Clean cast iron,....
No paint, No rust, just Clean, 'n Flat,...

Then toss those green gaskets, 'n get a set of Mercruiser's metallic carbon gaskets, 'n use 'em Dry,...
 
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