big difference between OEM/Aftermarket manifolds

[Rick Stephens]

No mater whose name is on them you should always take a fine flat file to both surfaces to make sure there flat

My GLMs have been perfect..... after I used a big bastard on the surfaces :^)

 

[bruceb58]

My GLMs have been perfect..... after I used a big bastard on the surfaces :^)

Salt water use? How many years do you have on them?

 

[Rick Stephens]

Salt water use? How many years do you have on them?

No salt water. until this year. Previous owner had some 300 plus hours on them, all fresh water. I did a rebuild on the motor and they still look like new. I was told these came with the boat when the PO bought it, something like 5 years for him. I asked since they were GLMs and I was curious. The gasket surfaces were just a bit on the ragged side, so I draw filed them a bit when I rebuilt the motor previous to install in my boat. I've used the boat some in salt water this year, but not enough to matter much.

 

[bruceb58]

That explains a lot. Not much of an issue with fresh water.

 

[samm835]

If you replace the manifold. ....most times do you replace the risers at the same time? I am pulling both this weekend, I'm 90% sure manifolds are due just not sure about the wear on the risers. Can old risers be used with new manifolds? 86 merc 350

 

[bruceb58]

If you replace the manifold. ....most times do you replace the risers at the same time? I am pulling both this weekend, I'm 90% sure manifolds are due just not sure about the wear on the risers. Can old risers be used with new manifolds? 86 merc 350

Risers don't last as long as manifolds so you should replace. General rule of thumb is you replace risers twice as often as manifolds.

 

[alldodge]

Risers don't last as long as manifolds so you should replace. General rule of thumb is you replace risers twice as often as manifolds.

Have any links/pages/etc that indicates this rule ? Always looking for new info, thanks

 

[bruceb58]

Have any links/pages/etc that indicates this rule ? Always looking for new info, thanks

It's what my local Volvo dealer reccomends and it's what I see after a few years of saltwater use and its what I do. The issue is that the riser has it's insides exposed to more air than the manifolds since that manifolds are full of water after engine shutoff and the risers are not. Also, the water is always hotter by the time it reaches the risers which also accelerates corrosion.

This is of course for saltwater boats.

 

[bruceb58]

http://www.boatus.com/seaworthy/swbtob.asp

Risers tend to fail before manifolds because the water is hotter by the time it reaches them, which accelerates corrosion and causes the salt to separate and stick to the walls more readily. Also, the top and aft side of the riser is exposed to both saltwater and air where the two combine, which is a perfect environment for corrosion, so you may get a few more years out of a manifold.

 

[alldodge]

Thanks, read that one before the posting, it basically says you can probably get a few more years out of the manifold but no guarantee.

 

[bruceb58]

Last time I didn't bother just replacing the riser. I replaced both at the same time. In any case, you never replace the manifold without replacing the riser.

Now that I use the Volvo NeutraSalt system on my boat, both manifolds and risers seems to last longer. Another one of DonS's great suggestions.

 

[samm835]

Anyone have a kit# handy for a 1986 merc 350/260? I can't seem to find the correct part numbers, closed cooled, also what does "will not work with dry joint" mean

 

[alldodge]

I would suggest searching on Mercruiser 860246A15 and Mercruiser 807988A03. There is also a 3 inch exhaust elbow under 98504A3 and cost more. There are kits, soft of, but then your talking about after market

 

[samm835]

I am just now getting around to ordering a set....but ran into an issue, which ones should I get "wet joint" or "dry joint", one better than other?

 

[alldodge]

I am just now getting around to ordering a set....but ran into an issue, which ones should I get "wet joint" or "dry joint", one better than other?

Dry joint is always better due to safety for the motor. Wet joints allow the possibility of water to leak between the manifold and riser gasket, dry joints do not.

 

[NHGuy]

Yours was wet joint when built but dry joint is available and far safer for the engine.
BTW the OE manifolds have "MERCRUISER" cast right in them no matter where they were made. And the ones I'd stay away from are the HGE brand. They looked so primitive I returned them. Really rough castings.
I love a bargain, but they put me off.