What do you guys think of the Mercruiser stainless risers?

[jakwi]

I found a pair of Mercruiser Stainless Steel Exhaust Elbow Risers PN 816900-C, for $250 Will they match up with my Manifolds? I have a Mercruiser 357 Alpha 4v. The part numbers that I know will work are:

2 - 807988Q03 Risers
1 - 93320A13 Spacer Blocks
2 - 860246Q11 Manifolds

Thoughts?

 

[wahlejim]

Unless you are in saltwater, I don't think it is worth it. The normal ones will last you decades in freshwater and will probably outlive the boat if you are replacing the originals right now.

 

[alldodge]

Don't see the term 357 V4 very often so had to look it up again, its a Merc 350 reman.

The elbow 816900-C is old style stainless riser which are no longer made, but many still have some old stock. There should be no issue using

I found port side at ship wreck for $174

 

[jakwi]

Yeah, it's just a bored out 350 block as I understand it.

http://www.boattest.com/engine-review/Mercury-Remanufacturing/32000129_357-Alpha-4V_2015

I am in salt water, which is why I was considering them. The pair I found is a used set and looks really clean.

The only differences I see are that the bolts won't go all the way to the top of the riser, so I'll probably have to find my own bolts, and instead of a threaded plug on the front side, there is a nipple, which will need to be capped.

Other than that they look like they will bolt right up, I just wanted to be sure.

 

[alldodge]

it's just a bored out 350 block as I understand it.

Correct, so if you just said its a 350 no one needs to go and try to figure it out. Just makes things a little easier

It should work. Merck found that the ones which have bolts going clear thru have a better seal.

Since your looking at used, found one on eaby for $96

 

[jakwi]

Yeah, I guess you are right. Sorry about that.

Good to know about the bolts, I guess that is the trade off. I'll take a look on eb

 

[achris]

When I had my 4.3LX I put those on. As the engine was also close cooled it meant I never had manifold or elbow problems again. Highly recommend.

Chris

 

[tpenfield]

I have the SS riser(elbows) on my older 7.4L's . . . It is a great combination with full closed cooling. I would not recommend the SS risers used with the iron manifolds and open cooling though. The SS will eat the iron alive.

 

[jakwi]

I have the SS riser(elbows) on my older 7.4L's . . . It is a great combination with full closed cooling. I would not recommend the SS risers used with the iron manifolds and open cooling though. The SS will eat the iron alive.

Really? why is that? my setup is open cooling in a mostly brackish water situation. I thought the SS riser/elbow would be a nice upgrade.

 

[achris]

Galvanic corrosion. Stainless is 'more noble' than iron.

 

[jakwi]

ah, ok, I figured since they were both "steel" that wasn't an issue, and I heard that Mercruiser stopped making them because of manufacturing difficulty. Ah well I guess that's out the window then.

 

[old bird]

I have them on my raw water cooled 454's . I'm in salt water, haven't had a problem. I always figured the gaskets separated them.

 

[jakwi]

I have them on my raw water cooled 454's . I'm in salt water, haven't had a problem. I always figured the gaskets separated them.

Thanks for your reply, how long have you been using them?

 

[Lou C]

Manifolds are cast iron, elbows are stainless, I don't the actual difference on the nobility scale, I think if you had a full closed system where raw water does not flow from the mani to the elbow it would be a non issue. If the gaskets really separate the 2 surfaces as they should, it really should not be a corrosion hazard, depending on the salinity of the water.

 

[tpenfield]

FWIW - When I bought my boat (2012) it had raw water cooling with the iron manifold and stainless steel combination. The manifolds had been depleted to the point where they were leaking exhaust into the engine bay.

The boat was 16 years old at the time and always in fresh water (Lake Winnipesaukee NH). I'm not sure if it took 16 years to deplete the iron manifolds, or if they had already been replaced along the way.

So, it will take a while (in fresh water) for the stainless steel to deplete the iron. Stainless vs. aluminum is obviously much faster. Salt water will probably be much faster. The question is . . . do you want to play that game? :noidea:

I think full closed cooling and stainless elbows is a perfect match for salt water.

 

[old bird]

I'm in the Chesapeake Bay, so, not that salty. I'v been replacing the manifolds every 5 or 6 yrs. My old Formula is a 1977. Wish I had closed cooling.