Stainless marine manifold leak

[larby]

Hi all,

While stripping down my motor last night I've found one bore has evidence of water ingress, though thankfully nothing too bad! All 8 exhaust outlets seemed to have 'crustiness' in too.

So I'm guessing I may have a crack or something inside one of the manifolds, allowing water from the jacket into the exhaust piping?

Is there anything I can do about this if it is the case? How could I best test to see if it is? Or do I just need to start saving for new ones

Cheers, James

[motorvator]

No 5? Could just be reversion so don't sling 'em away till you've checked. Do you have a habit of blipping throttle?

[larby]

Well standing at the bellhousing end, its on the right hand side, 3rd away from me, whichever number that is! Just seemed weird it was only that one? Could just be the way the valves were too I guess.
I never blip the throttle before shutting off, but last time it was run we did have it revving then shut down fast due to an issue...

James

[motorvator]

4. You,ve answered your own question. If the headers are leaking you would generally expect it in more than one cylinder.

If you shut down with any revs on, the overlap on the cam is sufficient to draw water back in as it stops. Lots of water from engine speed versus insufficient exhaust gas to keep it expelling if you see what I mean.

Never shut down with any revs on at all and avoid stopping dead in the water with with the throttle off otherwise the swamping will be sufficient to suck your flaps back the other way and hydraulic the engine.

Erm, I've heard

[larby]

Originally Posted by motorvator

the swamping will be sufficient to suck your flaps back the other way

The missus had that issue last year!!

Seriously though, that all makes sense, I'd never quite understood why the revs affected reversion so much, but do now!

So on that note, as it happens I was considering converting my exhaust to be a dry system, noise isn't really an issue, I can always put mufflers on if I need to. That would then solve this issue?

Is there anything to consider other than pretty much continuing the inner pipe to the end, sealing off the outer and adding a water outlet? The exhausts on mine are only about 1ft long, and very close to the water as it is, and the inner pipe currently ends right by the elbow from the manifold, surely this would be better off further from the motor or all the way to the end?

Cheers, James

[motorvator]

Originally Posted by larby

The missus had that issue last year!!


Cheers, James

I need to bleach my mind now

Originally Posted by larby

So on that note, as it happens I was considering converting my exhaust to be a dry system, noise isn't really an issue, I can always put mufflers on if I need to. That would then solve this issue?

Is there anything to consider other than pretty much continuing the inner pipe to the end, sealing off the outer and adding a water outlet? The exhausts on mine are only about 1ft long, and very close to the water as it is, and the inner pipe currently ends right by the elbow from the manifold, surely this would be better off further from the motor or all the way to the end?

Cheers, James

Dry exhaust or not the problem of swamping will always exist with your pipes low to the water. Think of it as the overlap on the cam will when slowing and getting to the final opening create a sucking effect (I.e. that cylinder is trying to get a litre of air from somewhere whilst the exhaust valve is still open) and then couple that with a wave coming up behind, and you can see that without solid flaps they can get sucked thru' the other way.

You will note I have saved you time reading the post in detail and have highlighted all the places you can now do a double entrendre. OOh there's another one.