Exhaust flapper

[Scott215]

Hi guys been reading a lot about these lately and want some opinions on what you guys think. I will finish out the season as the boat seems fine but don't know much about flappers

 

[Bill Curtis]

They reduce chances of water entering exhaust during hard deceleration or heavy following seas (or big wakes fitting a moored boat that is nose in). Usually if they make ticking noises at idle, the rubber is gone off them and need replacements.

What causes the failures is normally a loss of raw water flow through the elbows, either from plugged water passageways in the manifold and / or elbow or the loss of the raw water pump flow while running.

Or, the flapper shaft rotting away and the flapper falling down into the exhaust "Y" pipe. In that situation, it is in need of immediate attention, as the S/S shaft can eat through the aluminum Y pipe near the bottom or cause exhaust blockage. A borescope and a mechanic's "magic fingers" parts retriever tool will make job pretty easy.

Easy job to replace them if you don't have full closed cooling on the engine.

 

[Scott215]

It's raw water cooled 5.0 mpi in a 215 weekender no noise drive was off recently and no sign of anything. How long do they last and is there one on each side or just one at the y pipe

 

[Nater Potater]

It's definitely a Mercruiser thing. I just went through this on my '92. Twins, so double the trouble. For some reason, the flappers I got didn't want to fit into the Y-pipe without some massaging. 'Story of my life. Granted, I didn't get the genuine Merc pieces, as they were at least double the price of any others.
One of the old one's wasn't even there when we pulled the risers! In light of the fact that that side hadn't suffered any water damage, I question if they're really necessary.

 

[Scott215]

So my 5.0 mpi has 1 set or 2 sets 1 set at the end of the riser tube. Single 5.0 mpi 215 weekender, thanks

 

[scoflaw]

2 sets at the top of the y-pipe. Threw mine away years ago.

 

[Scott215]

I have heard both good and bad some people toss them and some say you need them boat runs great no noises on trailer or in the water. Will looked at end of next season of I do manifolds and risers

 

[Nater Potater]

I have heard both good and bad some people toss them and some say you need them boat runs great no noises on trailer or in the water. Will looked at end of next season of I do manifolds and risers

They're not needed as far as the engine's performance is concerned, and actually slightly cuts into max horsepower (very slightly). Their only purpose is to keep water from being pulled up into the engine when chopping the throttles to come off plane. Also the same reason marine cam durations/overlaps are different from automotive cams. I could get away with not having them as I always carry a bit of throttle until dropping back into the water, but I'm not the only one running my boat.

 

[Scott215]

I will check when I do manifolds thanks guys

 

[scoflaw]

They've been made out of plastic for quite some time now, so no more noise

 

[Scott215]

What do you think yes or no on replacing them or leaving them out

 

[scoflaw]

Maybe there is nothing wrong with them

 

[OllieC]

I replaced mine when I did the manifolds and risers last year. Simple to do and just checked it off the box as being done

 

[Scott215]

Absolutely not ma'am. Will be doing risers and manifolds next April. My old Larson 18 ft bowrider was nothing compared to this and this motor I'm my sea ray you could eat off of it. The Larson was just wide open with the 3.0. thanks again guys and gals