Riser interchangeability

[TheHunter990]

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.


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


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]

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]

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]

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,...