View Full Version : Raw Water Cooling System Questions

11-16-2008, 10:46 PM
I am in the process of repowering my Hunter 27. It currently has a Renault engine which I will be replacing with a Yanmar 2GM engine. Yesterday I disconnected everything from the Renault engine in preparation of pulling it out of the boat. Let me prefice that there are two seacocks. One for inlet water and one (I thought) for outlet water. I noticed that only the inlet water cooling water line was connected to the engine. And the outlet water line ran somewhere else but was not connected to the engine. So I began to wonder what the outlet water line is connected to and what is the purpose of the outlet water line and its seacock?

The Yanmar 2GM engine that I will be installing is also a raw water cooled engine and I am wondering if it also will be connected the same way?

Could someone enlighten me with some understanding as to how this cooling system works and what I might need to pay attention to when installing the Yanmar engine? Thanks.

11-18-2008, 08:59 PM
"Hi Rus, In some cases people would install a shut off on the exhaust side so a following sea would not come up the exhaust into the engine. A good plan untill someone forgets to use it or open it when running the engine. Now they use waterlock systems. Go into Vetus web pack and you can see their exhaust systems and how they should be installed. Vetus is a Dutch company that has been in that business for donkeys years. I hope this helps. Regards, Ron"

02-02-2010, 02:04 PM
"the exhast outlet (hull fitting) for my 3gm30 is fairly close to, but slightly higher than the exhaust manifold on the engine.. I will be fitting an in-line flap valve but I am unsure wether the engine can provide enough exhaust pressure to discharge the water fully. Any thoughts? oh by the way the boat is a St Pierre dory newbuild."

02-02-2010, 03:42 PM
Are you saying your exhaust thru hull is the same level as the engine exhaust manifold or the riser? Neither one is good but the later is fatal.

Either way you absolutely need to install a water trap muffler. The best ones I know anything about are made by Vetus.

02-02-2010, 03:58 PM
"Hi George, Yes Jimbo is right, Vetus make a good unit, go to their web site and they will have illustrations of how the exhast should be installed in your vessel."

02-02-2010, 05:10 PM
My boat (under construction) is a 23ft St Pierre Dory. As it is flat bottomed there is precious little space to put anything as big as a water trap muffler. The only item that I may be able to fit in would be a non-return(flap)valve assembly. The original exhaust was to be out through the transom but as this would have involved a pipe run of around 12-13ft and required the notching of a few frames I abandoned the idea for an overside exhaust just aft of midships. The exhaust discharge will be at around the same level as the engine exhaust manifold. I will try and include a photo or two of the boat to give you a better idea of what I am up against