What does this do?

[Ventura I]

181874 1986 150 XR2, water is leaking out of the hole. I know why, rubber diaphram under the cover is ripped. But what does it do? Does anyone know the P/N, cannnot find it to order a new one. Maybe some sealant on the tear can get me through until I can locate a new one?

Thanks,
Fred

[hotbeek]

That houses your poppet. That hole will weep water when diaphram breaks.The poppet controls cooling water flow for mid/hi-speed operation, is supposed to unseat and flow max water. I doubt you'll be able to repair the diaphram.

Check for your parts here:

http://www.mercruiserparts.com/selectModels3.asp?type_id=MAR

I think you're looking for part number 648771. You may also need the gaskets too.

[Ventura I]

Yes, found it, hidden under Exhaust Manifold and Exhaust Plate. 648771 seems to be the p/n.
Thank you