Exhaust Run Question

[JohnV8r]

Guys,

I need advice on the exhaust run now that I'm moving my exhaust outboard of the outboard stringers to make room for in deck fish boxes. In looking to see if I had bonding wires on my tiller arms from info I received on another post, I realized both my port and starboard exhaust runs appear to angle downward from the exhaust thru hull to the transom end of the muffler. From that point, it appears the whole exhaust angles slightly upward. Here are the pics:





Based on advice I got from Bob Lico to move the mufflers as close to the forward bulkhead as possible to avoid having to raise the deck to have Vernatone mufflers under the deck, I am intending to have approximately 4-5' of a straight shot of exhaust hose out of the muffler to the exhaust thru hull. I'm concerned the additional straight shot of exhaust hose will potentially create more momentum from water heading into the exhaust hose from the thru hull.

Here are my questions:

1. Should I create an additional cradle and strap to force the exhaust hose down toward the bottom of the hull at the same angle it currently has to create a longer flat or slightly upward angled section heading into the back of the muffler in its new more forward position?

2. Should I keep the new outboard exhaust thru hull the same height as the current thru hull when I move it more outboard from its current position?

3. Anything else I need to know about moving the exhaust outboard to create in deck fish boxes?

Thanks!

[Tony Meola]

John

There is one other option that I saw on John Jackson's boat. John does not really come on the board anymore, but when they redid his boat, they ran the exhaust down the outboard side, but left the ports in the same position and put I think it was two 45 degree elbows at the end of the run so they mated to the old ports.

If I remember right he had some back pressure with the 5 inch hose and had to go to six and I believe it reduced to 5 at the port.

Just a thought. Still gives you the shaft alley for fish box's.

[JohnV8r]

So I did think of that, but here's what concerned me. I'm pretty sure this is Bob H's "Resolute" in both pictures. In this first picture, he's got the exhaust thru hull glassed in the way I've decided to do it. If I used two 45 degree elbows, it appears from this photo the elbow closest to the transom would have to angle up slightly to get over the stringer. That would mean I'm tall at the transom on the exhaust run, thereby making it a downhill run for water entering the exhaust at the transom.



In this picture, he's got the fish box in place. You can see he's patched the initial thru hull and moved the exhaust outboard of the outboard stringer. Looking at this photo and how relatively high the cradles are off the hull bottom, I think I could keep the exhaust hose low enough to keep the muffler in place under the deck without raising the deck height.



I may just have to get in and start playing around with the exhaust pieces to figure out what works. I'm trying to keep from ordering the wrong pieces, but it may be less expensive than the mental hospital I'm going to end up in if I keep waking up in the middle of the night with new ideas.

Am I overthinking the exhaust angle issue give the height from the low elbow to the risers?

Maybe I should just run the exhaust out the sides instead of the transom...

[Tony Meola]

John Cranston ran his out the side. Search for Real Cowboy and you should find pics.

[Tooeez]

Here's another thought: my 79 has the factory side exhaust mufflers, which sit outboard of the stringers about a foot forward of the transom. They basically divide the exhaust into dry and wet, sending the (mostly) dry gas out the side exhaust slot, which is located about 10 inches under the gunwale, and the water, which exits out a small (about 1 1/4 inch) transom port. The drawback is a bump-out into the cockpit where the vertical part of the mufflers is located. The good part is a much smaller opening for water to back up into the system, and they are so quiet you can talk in the cockpit at cruising speed in a normal tone of voice. If you wanted to go this route I am sure that someone, somewhere, has a set of mufflers that were removed during a repower (the gas powered 33's used the same system, but I don't know if the mufflers where the same size).

[JohnV8r]

OK Tony,

Now my head is really spinning. Running the exhaust out the sides might be the more simple solution for me since it would eliminate me having to move my outboard swim platform supports slightly inward. I dug up some old photos and found the Reel Cowboy photos as well. It appears to me that Reel Cowboy has the exhaust right on the corner of the transom from this photo:



This photo of the Super Mex restoration shows a more forward position:



These photos, also from the Super Mex restoration, show the actual exhaust run:





I originally thought running the exhaust out the sides would simply take a Centek 45 degree elbow (or really a 225 degree angle). However, looking at the Super Mex photos, that angle looks more like a custom 210 degree angle. Creating a custom angle with a miter saw and a 6" fiberglass exhaust tube is simple enough.

Are there special epoxy resins or layup materials required to join two fiberglass exhaust tube sections due to the heat of the exhaust?

Are there any disadvantages to running the exhaust out of the sides rather than the transom?

Thanks!

[Marlin]

I did 6" side exhaust ,mitre the angles dry fit til happy with the exit profile, put some 5 minute epoxy in the but joint as a way to hold /fixture in place during removal for several layers of 1708 and epoxy as a wraparound bandageon the bench. Let it kick, dry fitted and had to do some touch up grinding to get the profile I had originally planned, tabbed the pipe on the inside with 1708 ,numerous strips all around the angled section to the hull . I had fixtured the preassembled pipe to hold in the position I wanted. On the outside I trimmed the end of the extension coming thru the hull to get the front edge probabably 1" more proud than the back, which was still out1" , mixed up some epoxy and vermiculite into a thick ,packable mass ,used my gloved hand to push this stuff into the crack and shaped to get the fairing I wanted,all around the pipe extension, next day, used a round rasp used to work on bondo ,shaped the profile, tabbed on 2 stepped layers of 1708 , cured , hand shaped it again, faired with peanut butter cavosil epoxy, faired, another coat of micro balloon epoxy, ready for finishing. I'm not a purist and wanted the retro look,lots of room then for fish boxes that can hold a large human,I case I ever need to

[JohnV8r]

Marlin,

Thank you for that!

How much of the exhaust in front of the angle was fiberglass exhaust tube? Did you run solid exhaust tube up to the muffler and connect with a short piece of Trident exhaust hose or did you just make the angled fitting with enough length parallel to the hull side to get a longer piece of Trident exhaust hose properly secured between the muffler and fabricated side exhaust thru hull? I'm wondering how much solid exhaust tube to run.

Thanks again! I really appreciate the input.

[Tony Meola]

John

As far as exhaust heat, I have never used a temp gun to take the exaust temp, but given that most of us today use glass elbows much closer to the engines with no problems, I would say that the exaust temp is much cooler 8 foot back plus it is mixed with water which helps cool things down.

Exhausting out the sides eliminates the station wagon effect you can get when exhausting out the back. Also pretty much cuts down on the possibility of water backing up the exhaust when you are at drift or backing up hard.

[Marlin]

As I recall, I ran a piece of fiberglass tubeing maybe 2' from the angular connection, with a saddle support secured to the bottom and strapped over the top of the exhaust pipe at that position . I kept the forward leading edge of the extended side exhaust proud to create a a defecting path of water as it passed by this protrusion. I did the same concept when I installed a bow thruster on my 42' to divert the water from re entry back into that aft space. I got all this info on a daily basis by the infamous Capt, I miss his tutorage. Who would ever think about using plant bedding(vermiculite) as a mixture with epoxy,people still challenge this concept,holds up in 8' seas in the bahamasas and no spray in the cockpit

[Marlin]

The saddle supports for the f/g exhaust tubs as well as all the deck support system , rudder shelfs, strut backup plates were made of coosa board, plywood is antique construction means . I want my boat to be around another 50 years for my grand kids