Reallocate exhausts

D

daray

New Member
Jan 3, 2016
5
Netherlands
Boat Info
260 Overnighter 1989
Engines
2x Mercruiser 4.3 v6 Alpha one
Hi all,

I'm Ray from the Netherlands and I have a 300 Sundancer with twin v8's. My boat has open exhausts and that's where the problem starts.
We've enjoyed a nice holiday on the boat but the continuous loud and deep sound from the exhausts doesn't help enjoy boating with my boat but even more important is the issue regarding carbon monoxide. I have alarms on the boat and they will sound everytime we go out there. It helps when I close the backside of the canvas but since I also have a young son I dont want to take any chances.

Now, since I really like the boat I was wondering if there is a possibility to reallocate the exhausts openings to below the waterline. Maybe someone on the forum has done this already and can share experiences?
The engines have been completely rebuild last winter so this should not create the issue with the co2 so the only thing I can think of is reallocate the exhausts.

I hope someone can provide me with some advice because otherwise I'm afraid I have to sell the boat.

Thanks
Ray
 
Welcome! I'm sure some folks smarter than me will chime in. Many of our boats have split exhaust, above and below the water line. Rather than cutting holes in the hull of your boat I'd wonder if there is some kind of muffler you could install instead? That may not help with the CO issue, but would quiet the boat down.

I think a lot of us deal with the exhaust smell/CO when we're boating in the direction of the wind. Gotta go faster...or turn around :)
 
Is the issue the noise or the CO?

If noise, you can possibly add some water lift mufflers, but there is a lot of piping and space required. I would have thought the boat would have this equipment from the factory. Was it removed or modified?

As to CO, you can move the exhaust underwater but the threat is still there and needs to be managed.

As a practical consideration, I think selling this boat, and getting into something with underwater exhaust as standard equipment will be easier and likely more cost effective. At some point Sea Ray moved to underwater exhaust, maybe in the early 90’s depending on model.
 
Install a Y pipe on the Alpha transom assembly and fill the holes on your transom where your exhaust exits now
 
Do you have sterndrives or inboards in your 300? What year?

But, assuming inboards... yes, look into a water lift exhaust. Someone must have changed things somewhere along the line because the boat would not have come with straight exhaust. You also might look into inline or transom silencers/mufflers depending on how things are setup (Corsa, for example). That should at least tone things down somewhat.

For the CO... yes, it is common to get exhaust backfeeding into the cockpit with the stern canvas off. Google "station wagon effect". If you open up your forward deck hatch and keep the cabin door open, that is often enough air flow to counter the effect. The whole idea is that you need airflow through the cockpit - it doesn't have to be a lot.
 
Thanks for the replies so far.

I think I had to provide some more info.
The boat has v-drives, so shaft propelled. The original mufflers are still installed but the noise is like a deep monotone sound. It's a bit annoying but if I keep revs on an certain level its not that big of problem. However, it would be nicer to have it more quite.

But the sound isn't the main concern, thats the co2.
 
The most practical solution may be simply a co2 detector. Even underwater exhaust will produce exhaust gases. I'm sure you are familiar with the station wagon effect whereby exhaust gases are drawn forward into the boat as the boats forward motion creates a vacuum which can draw the fumes forward. Worse in sedan boats than express. Good luck.
 
You said you are leaving the canvas on. That is probably why you are getting exhaust being sucked back into the boat. The way to minimize that at lower speeds is to open your windshield vent to allow airflow. I also open one or two hatches in the cabin and turn the locking handles into the groove in the frame so each one is just open an inch or so. That allows air to be forced into the cabin and helps keep the exhaust down.

That make not work if it is raining hard, but at slow speed its possible that there won’t be rain getting in.

As of the sound, V8 inboard engines are going to make some noise. I love the sound, but my wife does not.

One thing to check is whether your engine impellers are in good shape. I find that when they start to fail, less water flows through the exhaust, and its a bit louder.
 
OP hasn't been around in 17 days. Probably sold the boat by now...for 30% above asking price....:)
 
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