Swan 36 exhoust check valve

My swan had a check valve in the exhoust up near the low point in the back lazzerette to prevent the exhoust filling with sea water when healed over or when hit by a following wave.

I have recently had the flapper in this check valve fall off and slide back and plug the exhoust causing damage to the engine. Running raw water into the oil pan.

Is having a check valve in the exhoust common in the swan 36? Or is it something the previous owner installed as his own idea? Should I remove it or leave it in?

Thanks

Dear Taildragerdriver
The checkvalve has been put in afterwards, and should better be removed.
It is suggested you arrange the exhaust so there is a loop up to deck level on the centerline. The further forward the better, just aft of cockpit or under bridgedeck.
If you have a wet exhaust now the waterlock should have a drain cock, which can be kept open in hard weather.
Kind regards
Lars