Raw water bypass valves

[madhatter1]

Anyone familiar with these? I have them on my 46 with 8-92's. Trying to figure out just how much or how little water should actually dump at cruise RPM.

 

[warrenw]

Anyone familiar with these? I have them on my 46 with 8-92's. Trying to figure out just how much or how little water should actually dump at cruise RPM.

From what I understand the proper way to do it is with a manometer attached to a test port after the turbo to measure exhaust back pressure. The raw water bypass valve is adjusted open until the full load exhaust pressure meets the engine manufacturer specification. Ideally you would check the exhaust temperature after the showerhead to confirm it is still getting adequate cooling. My 47 Commander has a plaque in the engine room that outlines the requirement. Of course I don't have a picture of the plaque .

 

[divert00]

Where is bypass valve located on Hatteras 50 convertible?

 

[madhatter1]

Easy to see on my 46 just by following the hoses to the faucet type adjuster and then to the side through hull. I haven't found anyone that knows how to adjust them so winging it.

 

[Captain Ralph]

I remember on an ole Roamer with 12V71TI's, relief valves to a side hull outlet.
We just left these valves wide open.
Never an issue 25 plus years later.

 

[warrenw]

I remember on an ole Roamer with 12V71TI's, relief valves to a side hull outlet.
We just left these valves wide open.
Never an issue 25 plus years later.

I found the raw water bypass valves were wide open on both Cummins VT8-370Ms in my 47 Commander. For reference, the through hulls were 2.5", 2" outlet into exhaust showerheads and 2" overboard bypass. So roughly half of the raw water was being bypassed overboard instead of entering the exhaust. When I repowered to 375hp 3208TAs they pump less water so rearranged the exhaust setup so the 2" raw water bypasses are now exhaust bypasses and I put in 1/2" through hulls as raw water telltales. It's easier to pop out either wing door and look down the hull side to check for raw water flow then try to check at the main exhaust outlets.