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  #1   IP: 50.230.13.20
Old 09-29-2020, 11:23 AM
cfergu22 cfergu22 is offline
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Manifold Fitting Broke off

Background...

Raw water cooled engine, seems like the original manifold. Over the past few seasons the manifold has gotten clogged a few times a year, and it's gotten worse. Usually a quick pressure flush fixes it right up. A bunch of black crud comes out, then it works fine, until we leave it sit for longer than a few weeks it gets blocked again and we pressure flush it. About once a year I do a vinegar flush and that helps for a while. The blockages are almost always on the manifold side. A few years back I had the water jacket side plate off and scooped a whole lot of black crud out of there.

New Problem...

So this weekend, we tried to take the boat out for the first time in about 2 months. The manifold was clogged so I tried to do a pressure flush. But it wouldn't come unclogged. I tapped a few times with that back of a screw driver on the side of the manifold and a trickle started to come out. But then a tiny pinhole leak came out of the bushing fitting for the back of the manifold water outlet. It was unclogged enough to get some vinegar in there.

The vinegar sat overnight. When I came back the next day it came completely unclogged with the pressure flush, however the pinhole leak in the fitting was much larger now and spraying hard. So I sprayed some penetrating oil on the fitting and put a wrench on it to see if I could remove it from the manifold.

Unfortunately it was completely corroded and just broke off instantly with minimal pressure from the wrench.

Now I have a very corroded fitting that seems to be fused into the manifold and nothing to bite onto to get it out.

My question is...

Should I waste time trying to get the fitting out to salvage this manifold, or will all my problems with the clogged manifold be fixed by just buying a new manifold. I certainly don't want to have to spend the money, but not knowing if the engine is going to be clogged every time I go to use the boat is getting frustrating. The pinhole leak might have been happening for a while, because the outside of the manifold is very rusted.
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  #2   IP: 155.186.122.195
Old 09-29-2020, 11:59 AM
Dave Neptune Dave Neptune is offline
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Exclamation

First, use brass or bronze fittings nor iron when attaching to iron.

Second why all the flushing and plugging?

Why is everything so rusty, has to be from a leak somewhere? The manifold may or may not be salvageable a judgement call. It looks like it should be pressure tested before anything else and the broken fitting will need to be fixed to test. And the freeze plug looks like it is ready to leave the manifold too.

My guess is a new manifold and that will probably require some work on the hot section of the exhaust as it will need to be removed and reattached. The exhaust looks well past "undoing" so a replacement of it will probably be necessary too.

Dave Neptune
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  #3   IP: 50.230.13.20
Old 09-29-2020, 12:11 PM
cfergu22 cfergu22 is offline
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Yea, the PO did the fittings. But it's clear he should have used bronze or brass. My guess is that reducing bushing was put in a long time ago. We've only had the boat for 8 years and it was on there when we got it.

I'm not really sure about why it kept plugging. My thought is that it's just rusting from the inside and clogging up. There's always black crusty chunks that come out after its unclogged. So I don't think there's a piece of a pump impeller in there. It's more of a chronic problem. I'm sort of looking for some guidance, is that just what old manifolds do when they're past their prime?

As for the exterior rust, I think the rear manifold stud might have been leaking. It came out when I removed the manifold. Also, that fitting might have been slowly leaking and oozing down on that exterior area of the manifold and cause all that rust. I had the manifold off about 6 years ago and rebuilt the exhaust. it was not that rusty at the time.
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  #4   IP: 32.211.28.40
Old 09-29-2020, 07:49 PM
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Al Schober Al Schober is offline
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You can keep struggling with what you have. I did that for years. After a while it stops being fun. This time is usually when you spend more time working on it than enjoying it.
Three recommendations:
1) Acid flush the block.
2) Install a new manifold.
3) Change to glycol cooling with heat exchanger.
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  #5   IP: 50.230.13.20
Old 09-30-2020, 10:28 AM
cfergu22 cfergu22 is offline
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So the Manifold made the decision for me.

I removed the exhaust flange last night and the part of the manifold that the flange bolts go into just crumbled away. Now there's nothing to put the flange bolts or studs into. The manifold also crumbled away a little bit where the flange seals to the manifold so it wouldn't be safe anymore even if there were enough threads to accept new bolts.
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