Valves in the exhaust system of diesel engines are a mixed blessing.
Detailed correctly they offer protection from humidity in storage, and from boarding seas underway in heavy going. Their necessity depends on the type of cruising being done, the exhaust design, location of exhaust, and in particular the height of the exhaust riser.
The FPB 64s have shut off valves on both the engine and genset. In 99.99% of conceivable situations these will not be required. We are fitting them for a worst case scenario, where propulsion is lost and the boat is hove to behind a para anchor, or hanging on a drogue off the stern.
Being in the exhaust line the valve body can potentially accumulate soot and salt, so the valves should be periodically cycled to maintain their freedom of movement.
Posted by Steve Dashew (October 25, 2009)
October 26th, 2009 at 6:49 am
Hi, is there a reason for not using mikalor hose clamps? They are wider, stonger and they look good too!
Thanks alot, i just love your boats!
Gilles.
October 26th, 2009 at 9:54 am
Hi Gilles:
I am not familiar with these.
October 26th, 2009 at 9:46 am
Hi Steve,
Why not go with dry exhaust?
October 26th, 2009 at 9:53 am
Hi Kevin:
We have looked hard at dry exhaust systems and have discussed this in detail elsewhere. They have one advantage, getting rid of the salt water cooling pump. Offsetting this are a series of disadvantages. They are noisier and dirtier, more complex to maintain if properly insulated, and present a variety of moisture risks to the engine at rest and from condensation. Periodic replacement of the isolators, muffler, and exhaust line is a huge project.
Against this impeller maintenance looks pretty simple, as long as you have good access (which we do).
October 26th, 2009 at 3:54 pm
Thanks for the answer on my dry exhaust question. What is FPB#1 launch eta date?
October 27th, 2009 at 12:20 pm
Kevin:
Launch dates are always tenuous, especially on first boats. We are expecting (hoping) to start builders trials in February.
October 30th, 2009 at 3:50 pm
Hi Steve,
Does this system also have a loop, water lock, and flapper valve? If so, do you still feel it necessary to close the valve in the situation you described?
Just wondering if I should consider this on my (future) boat.
Thanks!
Scott
October 30th, 2009 at 4:04 pm
Howdy Scott:
The exhaust lines for engine and genset run to the deck. They also have aqualift style mufflers and external flaps. 99% of the time these will take care of any water ingress issues.
The valves are in place for two situations. First, for use when the boat is in storage mode, these eliminate humidity from outside getting into the exhaust system. The second, as mentioned in the blog, if you are in heavy weather, disabled,and hanging off a para anchor or stern drogue of some sort.
November 10th, 2011 at 11:55 pm
Would a regular steel valve or plastic valve be able to stand up to the corrosive exhaust gasses or are you using stainless steel valves?
November 11th, 2011 at 4:11 am
Hello Anders:
Plastic works as long as you don’t have a dry running condition under load. Mild steel is the norm, and will last years, as long as you exercise it on a regular basis.