Exhaust "ticking" noise heard from exhaust outlet until cooling water starts to flow

Caveman22

Caveman22

Active Member
Mar 6, 2020
217
Boat Info
310 Sundancer 1999
Engines
350 Mercruisers Blue Water, V drives
My 99 310 dancer with 350 mags and V-drives has a "ticking" type noise heard from the dock coming from the starboard side exhaust discharge until the cooling water starts to flow. It is not a leaking exhaust manifold gasket, definitely seems to be coming "through" the exhaust tubes / pipes.

Has anyone ever experienced this?
 
Where would this flapper be? In muffler or inline somewhere?
 
Sorry, am not familiar with your inboard set up. I have heard similar with i/o on occasion when starting on a trailer with muffs. It came to mind and was mentioned somewhat as a question.
 
Thank you for offering your advice anyway.
 
It’s your flapper, I replaced one last spring, it’s metal with a rubber edge that wears off after time. About $80 for original Merc part, lots of aftermarket on amazon for $25
It’s inside the downpipe coming off the riser.
Only does tick at idle cause once engine gets over idle the pressure keeps it open.
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Okay I understand understand that the V drives don't have these exhaust Flappers, is that correct?
 
You may be hearing valve train noise through the exhaust until the muffler fills with water. Warm it up and at an idle put a “mechanics stethoscope” all over the valve cover and listen for ticky valves. If you cant hear anything, open your favorite beer and go for a ride and enjoy your summer
 
Could it be an issue with the manifolds or risers causing this noise?
 
It may be a lifter ticking until it pumps up with oil.
 
I will be starting her up in a couple of weeks and I will keep you posted on what I find the noise was definitely coming out of the starboard side above water exhaust Outlet so I don't believe it's a ticking lifter
 
Possibly the exhaust flappers (just below the elbow after the riser) flopping around until the water gets in there. My last 7.4 Bravo did the same thing before I replaced the worn out flappers
 
Found bad exhaust valve seat! Pushing compression past valve on compression stroke! Thought I would find a burnt valve, but it's a chewed up seat! Also the exhaust manifold and cylinder head were kind of eaten away at the center point between the 2 inner exhaust ports! Is this common?
 
Would not say common. Sounds like damage from a failed manifold/riser. Did you pull and check the other side as well?
 
No, compression 180 in all other cylinders. Did pull exhaust manifold and riser the other side though. Am replacing those gaskets as well.
 
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