Genset exhaust routing

[1969Roamer46]

I realized a while ago that the port side of my project boat is getting heavily loaded compared to the starboard side. To balance the boat better, my best option is to relocate the Fischer Panda 12k genset from the port main engine stringers to the main stringers on the starboard side. This is a 1969 Chris Craft Roamer 46, and the genset exhaust thru-hull is welded to the hull. The Awlgrip paint job is done, so I’m not willing to make new holes in the hull.

Moving the genset from one side to the other will take some Egyptian engineering, since there’s not enough overhead space for a gantry, but it won’t be too difficult. But I was hoping for some input on exhaust routing. Panda’s installation instructions have tempted me to put in a loop above the lift muffler (see the rendering below), since there’s no practical way to have the exhaust hose drop 1/2″/ft as it spans the 8-feet from the OUT side of the lift muffler to the exhaust thru-hull. With the loop option, even if the 8′ section of horizontal hose didn’t drain immediately upon shutdown, with normal rocking back and forth, eventually it would drain.

Thoughts?

Thx, Q

Topic

[1969Roamer46]

It seems that every marine genset manufacturer in the recreational boating market is routing their exhaust in ways that violate Tony’s ‘inherently safe’ fundamentals. They all appear to exhaust at or near the bottom of their sound shields. Onan, Northern Lights, Panda…they all show preferred installations with goosenecks no more than 48″ above the waterlift mufflers. The post-muffler loop/gooseneck spillover heights on ALL of the manufacturer drawings I’ve seen are 1-3 feet higher than the showerheads.

None of them do dry stack risers that go up from the exhaust manifold and only introduce water after the pipe makes a turn, so gravity can take over. My Panda’s showerhead is pointing straight down, so we’re not fighting gravity from the riser to the waterlift muffler, but Panda tech support insists that the lift muffler MUST be below the genset; immediately under it is ideal, they say. They also said an exhaust gas/water separator should resolve concerns about a long run of horizontal wet exhaust. But even there, the manufacturer’s instructions require them to be installed in a way that violates Tony’s golden rules of marine exhaust.

I’m stumped. The attached drawing is the best I can come up with, based on Panda’s recommendation. I’d be very interested to hear how y’all route your genset exhausts “properly.”

[1969Roamer46]

All of the heavy stuff is already aboard and in place. The genset is the only heavy item that “can be” relocated to the starboard side. If I leave it on the port side, I’d have to compensate with a ~half-ton of ballast on the starboard. And that’s already factoring in that my 8D battery boxes will be on the starboard side. Before I go the otherwise unnecessary ballast route, I want to make sure I’ve exhausted 😉 all of my other options.

The Fischer Panda installation manual appears to have been written expressly for sailboats, and they discuss at length the potential dangers of flooding the genset through the exhaust when cruising at a 45° angle with the gunnel dipping in the water. But it’d be a very strange day on the water to have that situation on a power boat.

The attached pic is what Fischer Panda recommends. But I know from Tony’s various articles and posts that manufacturer recommendations aren’t necessarily good. Ironically, in the section on raw water inlet routing, they cover installations that are above the waterline and below it. But in the exhaust routing section, the waterline is always well below the genset.

When you say “install a proper exhaust,” what do you mean?

[Rob Schepis]

I’d keep the genset on the port side close to the original discharge and install a proper exhaust and then find another way to shift a few hundred lbs of ballast (not really a big deal on a 46ft, 30K++ lb vessel)

1 user thanked author for this post.

1969Roamer46

[1969Roamer46]

No, I haven’t been running it in real sea conditions. I’m doing a 100% refit of a 1969 Chris Craft Roamer 46. The Fischer Panda genset is sitting on the stringers but I haven’t installed it yet. There currently is no exhaust system, though I do have the waterlift muffler that was sold with the genset and a new roll of 1-1/2″ exhaust hose. Getting the genset hooked up is next on my project list.

The Chris Craft OEM genset exhaust thruhull is on the port side, as indicated in my sketch, but for trim reasons I need to relocate the genset to the starboard side. I’d prefer to plumb the exhaust to the OEM Chris Craft thruhull because I don’t want to put holes in my new Awlgrip paint job if I can avoid it. 

The Fischer Panda OEM showerhead drops straight down to the bottom of the sound shield, takes a turn to exit the sound shield, where it terminates in a 1-1/2″ hose barb. The installation manual indicates the waterlift muffler must be below the genset and as near to it as possible. It also recommends a “gooseneck” loop after the muffler.

A fellow named Steve D’Antonio, writing for Professional Boat Builder, included a photo of a Panda installation that he liked in an article entitled Generators Done Right (photo attached, since I can’t link to the article here). That’s the same model and sound shield I’ve got, and it also has a big exhaust loop going over the top of the sound shield. I’d be interested to hear your thoughts on that. Or any other thoughts about how to connect the Panda exhaust to the OEM Chris Craft exhaust thruhull.

Thanks!

[Tony Athens]

Have you been using the generator at “sea” , (under real ocean conditions) over the past year, two or ?..If so, sketch your current system with all components, elevations , etc etc..

The one in this “sketch” would be 100% doomed to failure.. 

1 user thanked author for this post.

1969Roamer46

[Author]

Replies