280 Sterndrive


New member
12 Apr 2005
Can anyone help?

On the 280 there are two rubber pipes which exit each side of the colar. On one of the engines they are blowing alot of water/gas out. Can anyone tell me what is their perpose and where they connect to.

Thanks for any help.


Well-known member
30 Nov 2002
They are exhaust by-pass ports and most sterndrives have them, as at idle speeds it requires a lot of exhaust pressure to displace the seawater which fills up the exhaust outlet in the body of the drive leg. So it escapes via the small passages on each side of the transom shield, then when you accelerate the increased gas flow forces the seawater out of the drive leg and it exits through the rear of the cavitation plate on your drive or centre of the prop on a Mercruiser.
They are connected inside the transom shield to the main exhaust pipe, if only one engine is blowing gas from these tubes that is how it should be, so would indicate that possibly the other engine has a problem with the exhaust bellows, i.e. holed or disconnected allowing the water and exhaust to escape there instead of via the by-pass ports.