Mercury Standard V8 Exhaust 88-97

[MOBILEMERCMAN]

If find myself talking about Mercruiser stainless risers over and over again.
The are painted black, are non magnetic and look different from the other 4 inch riser Mercruiser makes. The potential problem with them leaking is because of the dissimilar metals and the resulting problems with the gasket. The two materials expand and contract at different rates. If you persistanely and regularly service and change the gasket you may not have problems.

I can't count the times I have come across the leaking exhaust and resulting loss of compression or failed engine. Often the gasket never get changed until a obvious problem has shown its ugly face. Leaking and weeping water into exhaust over time causes damage to heads and worse. I have noticed its a bigger problem in salt water.

I am not talking about every stainless riser on manifold. Most systems now pass water around the gasket surface so that the gasket only seals exhaust.

Here are pictures Identifing the two types. If you have them have your gaskets changed. If you are looking to buy a boat with them be sure to check compression and ideally have the motor leak tested.

I always recommend to my customers to change them to the cast iron type.

The top one is the cast iron one

13121

This is the stainless one below. Take note of the short bolts mounting it. It is the easiest way to identify it. You can use a magnet to further confirm if you wish. The stainless is non magnetic

13122

[Geronimo36]

I hear ya Jimmy, who at Merc came up with that brilliant idea!

I remember people getting a snow-job by the dealers thinking they had something better because of the stainless and how it would last longer!! LOL

My favorite manifold was and has always been the older style Crusader manifolds. I've even seen some people make dry exhaust out fo them with a blocking plate and stainless pipe!! They make a little more power than the merc logs as well!!!

[txriverrat2001]

Jim - didn't they have a TSB about an updated gasket for those as well???

[MOBILEMERCMAN]

Jim - didn't they have a TSB about an updated gasket for those as well???

They have been many revised gaskets. All band aids IMO.

If you are going to use the SS ones you better plan on changing the gasket every other season or more.

[Bertram38]

what about the good Merc gasket with the lead coated tin gasket, those are the best for just what you stated above, will not alow the gasket to be swedged out and cause failer.
Aftermarket compressed paper gaskets spell death to any motor. those are the problem!.
My 2 cents
Kurt

[Bertram38]

These pictured are the stainless ones, I have four of them. Seems to be OK for me. Just use good Gaskets. Merc I should Say, or Quicksilver.

P/S, note the green gasket between the riser and 6" extension, those are gone now, I replaced them after motors where broke in, found out about how bad those type of aftermarket gasket where, so I tossed them. pain to get off the metal also. Crappy Gaskets, I belive those are OSCO name brade, or GLM. same $hit.
Kurt

[rockfish71]

The new gaskets are made out of the same material as the Gm head gaskets and work.

[cpmarine]

Thing is they probably will last forever if you have a good gasket, or change your gasket yearly like Jim said. We used to have a pile of them in the shop in the scrap pile but I don't see too many of them anymore. Merc did the same thing with the 470. Aluminum block, cast iron head and either cast iron or aluminum manifold and risers.

[MOBILEMERCMAN]

Bertram I would suggest you change them every second season. No matter what they look like. If you don't let it get away from you they will be OK

[MOBILEMERCMAN]

Thing is they probably will last forever if you have a good gasket, or change your gasket yearly like Jim said. We used to have a pile of them in the shop in the scrap pile but I don't see too many of them anymore. Merc did the same thing with the 470. Aluminum block, cast iron head and either cast iron or aluminum manifold and risers.

The riser will out last the motor. The shame is when you lose the motor to a bad gasket. The gasket is expected to do a lot with SS on cast iron.

[insanity]

Wow I had no idea there were cast SS risers but was just thinking about it ealier today, that I should change out those gaskets especially since I have the motor out. It looks like I have the stainless steel ones, I never would have known.

[MOBILEMERCMAN]

There should be NO rust in the exhaust part of the manifold none.

[Geronimo36]

If it's leakin on the outside it's most definitely leakin on the inside!!! If you have a few rust stains on the manifold, get er done immediately!

[MOBILEMERCMAN]

Don't be fooled into using anything else. This is equal to mercury perfect seal.

http://www.smallparts.com/Permatex-Aviation-Gasket-Bottle-GROUND/dp/B00137FW4S

[insanity]

What about cylinder head bolts? I've read of this being used on those as well, is there a better thread sealer to use?

[Geronimo36]

What about cylinder head bolts? I've read of this being used on those as well, is there a better thread sealer to use?

I use the Aviation Sealer/Perfect Seal or Permatex PTFE. Perfect Seal also works well on intake manifold bolts around the water passages. You only need it on head bolts with blocks that aren't blind tapped such as MK IV and bowtie..