maint. on shutters

[KEVIN D TOBIN]

how long do shutters last ? I mean before they break apart and wind up down in the Y-pipe.
I just finished grinding and shaping the top of the Y-pipe so the shutters can work properly. Now I'm wondering how long I should wait before checking or replacing them

 

[scoflaw]

I threw mine away years ago..

 

[Pirate Lady]

If you mean the flappers in the exhaust pipes of an i/o, I just had my port side replaced after 30 years, starboard is still original.

 

[Henry Boyd]

how long do shutters last ? I mean before they break apart and wind up down in the Y-pipe.
I just finished grinding and shaping the top of the Y-pipe so the shutters can work properly. Now I'm wondering how long I should wait before checking or replacing them

The 496 does not have them at all, so a geometry exists that won’t allow water back flow.

 

[KEVIN D TOBIN]

The 496 does not have them at all, so a geometry exists that won’t allow water back flow.

How does that work, does it go out the sides ?

 

[BillK2632]

If you don't overheat the motor they will last indefinitely. First sign they need replacing is a clacking sound in the Y-Pipe where the rubber parts have worn away. I personally have never replaced them - but I have never overheated a motor either.

 

[Henry Boyd]

How does that work, does it go out the sides ?

The shutters stop water from flowing back through the exhaust that can happen when you throttle down. The boat slows and the wake behind you washes up on the swim platform (and up the exhaust pipe). At the same time the positive pressure in the exhaust drops and that causes the shutters to start to close. Any water reaching the shutter will push it closed. That prevents water from flowing into the engine. Meanwhile engine is still running and pressure builds up against the closed shutter and opens the shutter with enough pressure to push the water out.

Now if there is a high enough point (above waterline AND surge) in the exhaust system between the Y and the engine, water will never get back into the valve gallery. On our 496 the top of elbows actually compressed the sound deadening foam under the deck they were up so high. So if the boat has the right geometry with the engine (and more importantly the elbows) up high enough, you might get away without them.

As for longevity, they like the manifolds and elbows will rot out. It is inevitable. Water and exhaust gas are a toxic corrosive mix.

 

[scoflaw]

The set I removed were all plastic, no metal. Threw them away anyways. Slow down gradually and don't turn the motor off for a bit after the stop and you won't have a problem.

 

[Henry Boyd]

The set I removed were all plastic, no metal. Threw them away anyways. Slow down gradually and don't turn the motor off for a bit after the stop and you won't have a problem.

CharlieG went a whole season of one that rotted out and fell down into the transom assembly. They couldn’t figure why they couldn’t get any power out of that engine.

 

[scoflaw]

CharlieG went a whole season of one that rotted out and fell down into the transom assembly. They couldn’t figure why they couldn’t get any power out of that engine.

Exactly, could be more trouble than they're worth

 

[Jeff Delbuono]

I just did my manifolds, risers, lower shift cable and flappers. I plan on keeping a shedual of every 4 years for all this. Cheap enough and not worth the trouble when they go