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8.1L >>> No Exhaust Flaps?

C

carboncow

Contributing Member
Refreshing what we believe is a 1997 engine with 1700 hours. While my buddy was pulling it apart he noted it seemed odd there were no flaps in the exhaust tubes to keep water out. He thinks he sees the holes the would swing on and we think this engine may have been open before.

I thought I read somewhere a few people had issues with these engines taking in water cause the risers are not high enough...so maybe there is a design reason for no flaps?

Any thoughts?
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Docksidemarineservices said:
I think VP's actual wording was "They were proven to do nothing"
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Thanks. What is your professional opinion?

I swore I read some threads (somewhere) about the 8.1L having water ingress issues from what some considered lower then required exhaust risers...and a few having issues. Others added higher risers to solve such needs.

Would adding such flaps help mitigate any such concerns?
 
carboncow said:
Any comments on the risers needing to be taller on the 8.1L or are those comments prob unique to the boat?
Yes, rather unique to the hull and where the water line is in relationship to the upper-most portion interior passages of the exhaust elbow.

Previous owner had it for 15 years w/o nuking the values/pistons!
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I think that you will be safe unless you under-go a quick shut-down and were to encounter a wage surge at the stern.

Are you running the exhaust down and through the drive (OEM), or do you have thru-transom exhaust outlets with back-flow prevention flappers?
 
RicardoMarine said:
I think that you will be safe unless you under-go a quick shut-down and were to encounter a wage surge at the stern.

Are you running the exhaust down and through the drive (OEM), or do you have thru-transom exhaust outlets with back-flow prevention flappers?
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It's an OEM setup...no flaps but my buddy was suggesting them since he's doing the rebuild. He was just surprised it didn't have them since he claims most Merc setups did. I'l got with Dockside's recommendations to keep it as is and review the manifold height.
 
sandkicker said:
Exhaust thru prop or thru/under cavitation plate?
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That's a great question! I state that because I wondered the same. it appears to be the it's the cavitation plate but there is also an opening at the duo prop...so wasn't sure if that was also exhaust, water outlet or a vestige of different designs.

Found some photos of when I took delivery of the boat in the spring. It's out of the water for a season as we are pretty much doing a full restoration of it.

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