Cattitude

Seeing some images posted on leaky manifolds and the damage they cause has been quite a wakeup call.

I operate only in fresh water- about 60 hrs per year, most of it at 3-3500 RPM (65 hrs now). I do not want to spend money on replacement manifolds prematurely but i don't want to roll the dice on when my factory merc units will start leaking.

I will upgrade when the time comes to something that flows better- CMI's if i have the funds because they are eye candy and flow well.

I should mention that I am Whipple charged (454 mag efi) as it likely means higher EGT's or at least faster thermal expansion.

1) How long in hrs or years before fresh water takes its toll on these manifolds?

2) Are any aftermarket exhausts proven to be more reliable in terms of leaking or reversion? My engine sits pretty high in the cat and the ex "S's" down under the platforms, so I really dont expect reversion issues.

Thanks!

Cord

I had 470+ hours and 12 years on my manifolds and they still looked like new. BUT that's not to say that the riser gaskets didn't leak and wern't replaced. When people refer to their manifolds as leaking, most of them are refering to the riser gaskets going bad.

Cattitude

So how often should I plan to replace riser gaskets?

Cord

It's really hard to say. You see, until the gasket starts leaking really bad or develops an external leak, you won't know that it's leaking! It's not all that hard to pull the risers off, so I'd just plan on doing it every couple of years-then you'll be assured of a good seal. Also using some permatex on both gasket faces wouldn't hurt either. Proably would let you push the interval back a bit further.

Jayl13

My riser gasket (dont know how old) was totally desintegrated.
I mean NOTHING left but a tiny bit of grit where it should have been.
they are not that expensive, I was thinking of stocking up on a few of them and leaving them in the tool box and one or two on the boat for a change if I see a leak for whatever reason.
every 2-3 years, could not hurt to drain and pull the risers and see what condition they are in.
Mine just crumbled in my hand when I pulled them off (probably origional 1990 exhaust)
Lost a big palm size hunk of iron when I yanked the risers (that tube that sticks out that the water flows over)

Im going to start pulling mine every year just because i lunched my engine from this and I just bought this boat last October.

Better to spend a few bones on gaskets than have to pull 2 engines and get rebuilt and reinstall them because of somehting as stupid as a gasket that just desinegrates on you without warning.
My opinion.
Good luck
Jason

Breathe Later

Cat,

pulled my risers off @ 130 hours. See my post "how bad is this" or something like that. Wanted to go with CMI, but Whipple project and upgrades to outdrive maxed out credit card. Merc has a new gasket (don't bother with that loctite 510 chit) and I used ultra black on both sides of the gasket.

Check 'em now!

Mark S.

MACDAD260

If you pull the risers off to check the gaskets, also check the manifold and riser gasket surfaces for pits and rust. I pulled mine last year to check them (8 yrs old and 450 hrs) and found pits on the manifolds. The risers are the stainless steel type and looked like new. I took them to a machine shop and had them resurfaced. They still looked good this year when I swapped motors. The gaskets are only 8-9 bucks apiece. I think the machine work was about $30.

stevel

I have 350 hours and 11 years in freshwater without a problem. All 3 engines look the same. I check every few years and replace the gaskets.

Steve

Crazyhorse

The 1987 center-rise Merc manifolds on my 1980 Searay are in reasonably good shape, and I replaced the riser gaskets last spring when I installed the rebuilt engines. Another boat I work on is a 1985 with the original Merc manifolds/risers and it's also in good shape (freshwater only). But I've seen a lot of them that were in really nasty shape too. If you've got any doubt about their condition I'd encourage you to replace them.