Mercruiser 454 riser gasket question
 

Hello

I have a newly acquired a boat and I am going through it doing some maintenance. I removed the exhaust manifolds and risers and I have a question about what is the correct gasket to be using between the manifolds and the risers. The engine has a heat exchanger half kit, so there is raw water going into the manifolds as well as the risers. It is all OEM Mercruiser Horizon parts I believe. I would like to know whether the partially blocked off gasket is used in this application, or if the fully open four hole gasket should be used. I have included links to the two gaskets below. The gaskets that came out of it were the fully open, four hole type. The gaskets that came in my kit are the partially blocked off type.

Thanks in advance for the advice.

http://www.mercruiserparts.com/863724-gasket

http://www.mercruiserparts.com/863726-gasket

Open

Ok thanks

you need to post your engine serial number and year model and 100 % which app do you have ? MCM or MIE and is this a Horizon 4 sure - if so they were used for inboard apps. so is this what you have a inboard app ? You have closed cooling as you mentioned correct ? Do you have extension blocks between the risers and manifolds ? Is this a stock app 4 sure ? if NOT what do you have ?

What kit did you buy and are installing ? New manifolds and risers ? If so what brand ?

Whithout this info its a possible guess.

BUP

It is a Sterndrive. For sure Horizon, it is marked on the top of the intake manifold. Yes it is heat exchanged with the half system. The kit is just a Sierra Exhaust gasket set for big blocks. No spacers, just the OEM manifolds and risers. I am replacing the risers only with new OEM parts.

ENG: 0M000134 465202HN1 MERCRUISER 454 MAG BRAVO MPI Horizon
DRV: 0M117798 5231200N1 MERCRUISER BRAVO 1 1.50:1
TRN: 0L897586 6311001N1 MERCRUISER BRAVO MAG TRAN

Date of manufacture 07/20/2000

Mercruiser per your provided serial number and model number of your engine shows an open gasket part number 863726 and I believe that crosses to Sierra 18-2849 inwhich should be an open gasket as well.

Ok thanks. That's what I was leaning toward. I was doubting the parts manual though because it gave me the wrong ujoints by serial number.

I went thru Merc dealer site , best using the required serial number.

It is best to always use engine serial numbers and model numbers when looking up parts and info about the year model apps that a person is working on.

replacing risers? get a couple of these. http://www.ebay.com/itm/MERCRUISER-5...dW1jFm&vxp=mtr

Those stainless ones are desirable. Surprised they are offered that cheap.