Whatever you do - don't forget the anti-siphon loop. The person who previously owned my boat had the yard install a new exhaust elbow. They didn't put in a valve. One morning I went to check the oil before starting the engine and water came squirting out of the dipstick hole for 10 minutes filling the bilge. Talk about a heart stopper!
I installed a Vetus valve from Defender along with some exhaust tubing and all is well.