[clberkley]

Just purchased 1997 Mariah 18ft shabah. My first boat, this one is in excellant condition, however the engine was lookup due to water in cylinders. I rebuilt the engine and now find that the flapper valves have been removed from the y-pipes. I also purhased new exhaust manifolds for my V6 engine. ,while installing the engine, one battery was hooked up backwards, I have not started the engine yet I am trying to find a wiring diagram as it has an onboard battery charger and a master control battery switch which lets you select 1battery 2battery, or all batteries. Do I need the flapper valves? I believe the engine flooded due to the missing flappers.

[ColoradoDiablo]

YES , do not put that boat in the water without the flappers installed! You'll be putting in another new motor faster than the power went out at the Superbowl.
They run about 100.00 for the pair on Ebay. Just make sure you get the "New" style ones.

[Andy b]

Also, as it's your first boat. don't rev the engine before you shut the engine down!
seen it happen sooo many times and all you do is suck water up the exhaust into the engine

[John Rush]

Do you mind explaining that more in depth regarding to the revving while in the water? Thank you

[ColoradoDiablo]

I think Andy was refering more to a sudden shutdown while running across the water. When your at speed and suddenly throttle down fast(as in throw it in nuetral from say cruising speed)the water will back flow up the exhaust.
The flaps help to reduce the chance of a hydro lock , but by no means are they a 100% cure.

[John Rush]

Note to self on that one!

[Andy b]

As Colorado Diablo said but also I’ve noticed a tendency with people new to boating to "blip" the throttle before turning the engine off. (As you might with a car or motorcycle)
But with a boat this can cause the engine to suck water back up the exhaust and into the engine! Not good...

[clberkley]

I want to thank everyone for their fast and efficient response to my post. Now on to finding the exhaust flaps, again any ideas would be greatly appreciated, by the way I teach automotive technology at a local secondary school here in Florida so I am versed in that field, it just that boats are going to be a new favorite hobby for my wife and I.

[ColoradoDiablo]

Here is a place to start.

Water Shutter Exhaust Flapper 4 inch Y Pipe Mercruiser V6 V8 807166A1 | eBay

Just need to see if your pin holders are square or round.

[Andy b]

Originally Posted by clberkley

it just that boats are going to be a new favorite hobby for my wife and I.

have you told her that yet