Mercruiser riser gaskets - Restricted vs. Open

[allingeneral]

I went to buy some riser gaskets today for my Mercruiser 350 (1989 model) Alpha One. The parts guy gave me a "Restricted" gasket, and after pulling the port riser, I see that the gasket that is currently on there is the same type. Can I use an "Open" gasket to increase water flow, or should I stick with the restricted gasket that was on there to begin with?

Restricted gasket:

Open Gasket:

 

[brendanstl]

Re: Mercruiser riser gaskets - Restricted vs. Open

I went to buy some riser gaskets today for my Mercruiser 350 (1989 model) Alpha One. The parts guy gave me a "Restricted" gasket, and after pulling the port riser, I see that the gasket that is currently on there is the same type. Can I use an "Open" gasket to increase water flow, or should I stick with the restricted gasket that was on there to begin with?

Restricted gasket:

Open Gasket:

This is great, I was just getting on here to ask the same question about the same issue with the same year engine. Hope someone answers this.

 

[Don S]

Re: Mercruiser riser gaskets - Restricted vs. Open

You guys might want to look at this Merc service bulletin.

http://www.boatfix.com/merc/Bullet/99/99_10.pdf

 

[brendanstl]

Re: Mercruiser riser gaskets - Restricted vs. Open

I went to buy some riser gaskets today for my Mercruiser 350 (1989 model) Alpha One. The parts guy gave me a "Restricted" gasket, and after pulling the port riser, I see that the gasket that is currently on there is the same type. Can I use an "Open" gasket to increase water flow, or should I stick with the restricted gasket that was on there to begin with?

Restricted gasket:

Open Gasket:

Check out service manual #99-10 answers our question and from what I read we need the open gasket, my elbows bolt to the center of the manifold with no risers.

 

[brendanstl]

Re: Mercruiser riser gaskets - Restricted vs. Open

You guys might want to look at this Merc service bulletin.

http://www.boatfix.com/merc/Bullet/99/99_10.pdf

You beat me to it Don.

 

[allingeneral]

Re: Mercruiser riser gaskets - Restricted vs. Open

Check out service manual #99-10 answers our question and from what I read we need the open gasket, my elbows bolt to the center of the manifold with no risers.

I have option 4b from that bulletin... Raw water cooled with bypass from the thermostat to the front of the elbows. So, I put in the restricted gasket.

4b.
Raw water cooled engines with the bypass water from the thermostat housing going to the fitting on the exhaust elbow and the warm water from the thermostat housing going to the 90-degree fitting on bottom of the exhaust manifold:
Use P/N 27-863724 Gasket ? Restrictor between the exhaust manifold and the exhaust elbow.

 

[SSSuper83]

Re: Mercruiser riser gaskets - Restricted vs. Open

AWESOME. Just what I needed without even asking. Thanks again Don S for sure...

 

[Alumarine]

Re: Mercruiser riser gaskets - Restricted vs. Open

Don, thanks for the bulletin.

It was very timely for a friend I'm helping.

 

[nofuss]

Re: Mercruiser riser gaskets - Restricted vs. Open

This is why its good to check for simmilar threads before asking. I recently changed to 2 piece manifolds and the restricted gaskets came with my set. I was wondering why the restriction, it did not make sense.
Now I have the answer..I have the wrong gaskets. thanks Sir Don S.
Guess I need to get the right gaskets now

thanks
No Fuss