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Old 04-29-2009, 10:52 PM   #1
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Default Salt water getting into engine

Our boat is a 2001 3700SCR. Again I have a major engine problem with salt water from the exhaust cooling system getting in the engine. Work has been done by authorized Mercruiser mechanic who says may be a design problem. Risers and all components in excellent shape. Results in exhaust valve sticking, push rod bending, etc., etc. Ever hear of this? Getting very, very expensive.

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Old 04-30-2009, 02:11 AM   #2

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Default Re: Salt water getting into engine

yep...this happens from time to time..usually a riser leaking and sucking into the exhaust...

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Old 04-30-2009, 04:52 AM   #3
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Default Re: Salt water getting into engine

Its got to be a bad riser or manifold unless its down to head gaskets unless its coming back up the exhausts when you shut off the power but the little valves in the downpipes should stop that happening

But surly if work has been done before and its happened again, it wasn't fixed properly in the first place do you have any comeback with the boat yard?

I must say the standard manifolds and risers are a very poor design. I really didn't want to fit even new ones so I designed some new ones and had them made out of stainless.
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Old 07-09-2009, 05:25 PM   #4

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Default Re: Salt water getting into engine

I know this is an old post, but it's worth posting for others. What Gazgen is describin sounds like 'Reversion', which can dump water back into the engine through the exhaust valve's, even when the manifolds and risers appear structurally sound. The actual term is 'Resonance Reversion'.

here is a good doc which describes this process:

I've seen this happen with aftermarket manifolds which internally aren't designed quite the same internally as the OEM parts, such as Genuine Mercruser parts. There should be a small internal lip which should prevent reversion from allowing water to backlow into the exhaust manifolds. I had two friends who experienced this shortly after replacing Mercruiser Mainfolds and Risers with Osco manifolds and risers because (supposedly) the Osco manifolds and risers didn't have this lip or the lip isn't placed and /or sized correctly to completely prevent revesion. I've heard tell of a situation where the riser and elbow were not sized tall enough to prevent reversion as well. the doc above discusses this in detail and is worth reading by anyone who uses exhaust manifolds and risers.

This is just one man's opinion (FWIW) so for those who use and swear by aftermarket or Osco specifically may have a different opinion.
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Old 03-17-2014, 04:51 PM   #5
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I am in the process of remanufacturing the 8.2l engines on my 98 3700scr due to this reversion problem. My mechanic is suggesting 6 inch spacers instead of 3, along with turbulators and resonators to prevent water ingestion. Seems like a design flaw. Anyone else ?
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Old 03-17-2014, 09:06 PM   #6
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khendra welcome aboard. WOW you sure dug up an old thread.

Gonna have to see i others with the similar setup have anything to say here.
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Old 03-18-2014, 01:32 PM   #7

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3" risers seems too short. I thought 6" was standard.

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