Diesel cooling water exhaust

[rsmith]

I was looking at a thread that was talking about backpressure on underwater exhaust and it got me thinking about when I was a kid all the diesel boats had a thru hull on the side of the boat expelling cooling water from the engine. This was in addition to the rear exhaust. They stopped doing it in the 70's You could tell if a boat had diesels by wether it had water pumping out both sides.Could never figure out if it was a telltale like a outboard or reduction of back pressure or if you were backing down on a fish it gave the water somwhere to go. I'm sure Yachtsman bill or someone on here must know.

 

[bobk]

I won't tell you that I 'know' the reason, but can pass along what I was TOLD re my boat. The 48MY was designed as a dual mode boat and the exhaust was said to have been sized for the natural 671 base engines. When Hatteras began putting in turbo 6V92's with more cooling water flow rather than increase the exhaust size, they added a water shunt that allowed some of the water to flow out the side. This was supposed to reduce back pressure, but I always wondered about the effect of increasing the hot exhaust gas flow through the pipes and not the cooling water. My PO actually increased the size of the pipes when he did a refit, but it still has the side water exhaust.

Bob Kassal
Chateau de Mer
1981 48MY

 

[jim rosenthal]

My Striker 44 had a setup like you are talking about, and a pipe valve in the diversion line to regulate how much of the exhaust water went out the side and how much went out the tailpipe. I don't see the point in it, either; you would think that you'd want as much coming out the pipe to cool the hot exhaust gases, wouldn't you? Maybe it's to relieve back pressure in the water line to the showerhead? I have no idea. I would think that a properly designed system would allow for all the used cooling seawater to flow out through the exhaust pipe.

Apropos of something faintly related, I have seen some boats where the generator set cooling water flow exits through one of the main exhausts. This seems to have some advantages in that the noise is less (any splashing is inside the exhaust pipe barrel), especially if your stateroom is midships or forward.

 

[rsmith]

My Striker 44 had a setup like you are talking about, and a pipe valve in the diversion line to regulate how much of the exhaust water went out the side and how much went out the tailpipe. I don't see the point in it, either; you would think that you'd want as much coming out the pipe to cool the hot exhaust gases, wouldn't you? Maybe it's to relieve back pressure in the water line to the showerhead? I have no idea. I would think that a properly designed system would allow for all the used cooling seawater to flow out through the exhaust pipe.

Apropos of something faintly related, I have seen some boats where the generator set cooling water flow exits through one of the main exhausts. This seems to have some advantages in that the noise is less (any splashing is inside the exhaust pipe barrel), especially if your stateroom is midships or forward.

My Ohno generators have always run sooty and when we drift fish the side of the boat the gen exhaust is on ends up with a black mustash running the length of the waterline. IVe often thought of putting it out the back but I think the smell would curl around in the cockpit.

 

[yachtsmanbill]

All the manly stuff that Ive dealt with that had cooling water discharge OTS (over the side) had dry exhaust. I would think that any thing running through the boat you would want water cooled. Mineral wool blankets wrapped around 10 inch pipes under the beds would creep me out!
The sub had a side exhaust discharge for the onan also, but that was changed to a transon exhaust. At anchor the bow is generally into the wind and fumes get carried away. Guys always complain about that mustache! Even my gas boat is out the back... ws

 

[Genesis]

Many boats have too much backpressure due to cooling water discharge - one of the ways people "address" this is to shunt some of the water overboard separately.

This is ok if done judiciously, but whether it's enough to really get the backpressure down is another question. The right fix for this problem is to enlarge the exhausts, but that's lots of $$$$$$$$$ so......

 

[yachtsmanbill]

One of the YF experts modified his exhaust... was heard sayin, Ah' reckons' thars to much back pressure on them thar deezels... Ah'll jus plum in a couple a valves har an' thar an be able ta spoolem' up...

bubbas summation...

2. Consider the square well, with well depth V0, and width 2a, symmetrically placed about x = 0. First, measure the energy of a bound state from the bottom of the well, and then consider this as a problem for 'free particles' in the momentum representation. Show that a) [p,H] = 0, and that the expectation value of the momentum p = ± hk; b) outside the well, when E < V0, k is imaginary, so that u(x) = exp(±kx), with k = ik, in the x- or "real space" representation. In addition, give the reasons why we need to choose just one of the solutions, not a linear combination of the two, outside the well.

Second, consider the more usual starting point for describing a deep well, with V = 0 outside the well, and -V0 inside the well. Show that, if E < 0: c) inside the well, u(x) = Asin(kx) or Bcos(kx), but that it cannot be Asin(kx) + Bcos(kx), with A and B non-zero; d) Derive the equations needed to determine k and (A or B) by considering the boundary conditions on the wave function at either x = a or -a; e) Work out the k-value and the energy of the second odd-parity excited state if V0 is very large.

 

[DCMY #92]

Our 1965 41DCMY with 6V53s has a water shunt out the side and wet exhaust. I was told by a DDC mechanic years ago to regulate the side discharge to maximize water flow out the side while maintaining the wet exhaust hoses and tubes warm to the touch at idle. He said the exhaust would run plenty cool at speed and minimize backpressure if set up this way.

When I bought the boat 29 years ago she had a 3" exhaust on each main. She was originally a gas boat with the Detroits installed by the PO. It took me a couple of valve jobs to notice that the the 6V53 needs a minimum of 5" exhausts - so I enlarged them and installed new 5" mufflers. I set the water shunts as previously instructed. All has been fine for several years, except that the exhaust noise level is much higher than before. An owner of the same boat with original 6V53s and 5" exhausts suggested that I can close off the water shunts to reduce the exhaust noise. I haven't been able to try this yet because Loose Change is still at Rivolta Yachts undergoing her refit. As soon as I get her back I plan to try this. Unfortunately I don't have a convenient method of measuring exhaust back pressure so I'll have to let the cylinder heads tell me if they are happy the hard way.

 

[rsmith]

One of the YF experts modified his exhaust... was heard sayin, Ah' reckons' thars to much back pressure on them thar deezels... Ah'll jus plum in a couple a valves har an' thar an be able ta spoolem' up...

bubbas summation...

2. Consider the square well, with well depth V0, and width 2a, symmetrically placed about x = 0. First, measure the energy of a bound state from the bottom of the well, and then consider this as a problem for 'free particles' in the momentum representation. Show that a) [p,H] = 0, and that the expectation value of the momentum p = ± hk; b) outside the well, when E < V0, k is imaginary, so that u(x) = exp(±kx), with k = ik, in the x- or "real space" representation. In addition, give the reasons why we need to choose just one of the solutions, not a linear combination of the two, outside the well.

Second, consider the more usual starting point for describing a deep well, with V = 0 outside the well, and -V0 inside the well. Show that, if E < 0: c) inside the well, u(x) = Asin(kx) or Bcos(kx), but that it cannot be Asin(kx) + Bcos(kx), with A and B non-zero; d) Derive the equations needed to determine k and (A or B) by considering the boundary conditions on the wave function at either x = a or -a; e) Work out the k-value and the energy of the second odd-parity excited state if V0 is very large.

Is that Algae-Bra?

 

[Walter P]

All I can say about messing with regulating side water discharge is be very careful. I have a 1982 Series I 48 MY with 6-92 TA's. When I bought the boat it needed a lot of work not the least was a new set of mufflers and some fibreglassing of the plywood under them. Obviously there was not enough water coming out the stern and the inside of the mufflers were "cooked". Over the years (before me) the heat burned or melted off the resin inside and all that was left was a nasty bunch of fiberglass cloth and a very thin shell which leaked water through pores in the shell. I don't know if the heat was enough to start a fire, but the thought really bummed me out. Naturally I replaced all 4 mufflers and I installed valves in the side exhaust water outlets. I regulated the water valves a little at a time and kept checking the muffler temperature. I have no clue as to weather the valves are correct or not but the muffler temps are down to about 120 deg F (from almost 200). Bobk has a sistership as he described a couple of posts before this and his was modified to a larger exhaust system all the way back.

If I had my druthers, I would prefer the larger system all the way back.

By the way, how many of you folks check muffler temp while you're out running?

Walt

 

[yachtsmanbill]

Me. By hand.Ns arent supposed to get hot,just noisy.

 

[REBrueckner]

"how many of you folks check muffler temp while you're out running?"

Most likely check for normal exhaust water flow...those with exhaust temperature monitors can check via their gages.

I've been told engine manufacturers warrantied engines only after some basic initial checks for production boats when new models are introduced...exhaust back pressure, WOT RPM, etc. So I'm surprised that Hatt would have a few models or styles with exhaust issues. In custom boats, engine representatives would normally check individual installations.

I've posted about a brand new 42 foot lobseter boat I was aboard in Maine for her initial delivery. She had just been splashed about 5:30AM and my dog and I came by about 6:30AM...a brand new boat with a big Cat....there was a Cat factory rep there for the start up and sea trial. We got invited along, Tenants Harbor, Penobscot Bay Maine....He did not check exhaust back pressure but the boat was a production model that had been Cat equipped so they pretty much knew what to expect. What fun!!! The boat left immediately for Massachusetts and was to begin lobstering within a few days.

 

[ThirdHatt]

This was Ivana Trump's old Yacht, a 104' that was lost last week in Palm Beach due to a laundry room fire. Apparently the lint had clogged the dryer vent hose and ignited. After reading about this fire, I realized that this is a very sad yet very preventable accident. I cleaned the lint out of my dryer vent and replaced the upper section of the hose which had deteriorated. Sure enough, this had not been done in some time as there was lint buildup at each bend of the hose.

WHile I am sad to see the loss of a boat due to fire, at least all 13 people on board survived. This will hopefully make everyone with a clothes dryer on their boat CLEAN THE LINT OUT OF YOUR DRYER HOSE ASAP! I know that I sure did, and added it to my list of regular maintenance items.

 

[rsmith]

Yep the old dryer trick. Seems we get about 1 blazing boat a week down here in the land of palm trees and dryer fires.

 

[Walter P]

Rob,

I am not referring to exhaust temperatures which serve to warn us of engine problems. After the water and exhaust mix, some is sent through the mufflers and out the back while most of the water was diverted out the sides. My issues were caused by not enough of the exhaust water being run aft to keep the mufflers cooler. Simple to check with an IR device.

Walt