Bad exhaust design?

[raleighm]

My A4 is installed on an Ericson 27. While engine access is good, there is little room for a waterlift muffler to be installed below the water injection point. The installation as it was when I bought the boat has the muffler mounted above the water injection point and at or slightly above the waterline. There is a riser mounted directly aft of the manifold exit flange that puts the water injection point a few inches above the waterline. Exhaust hose runs down from the bottom of the riser to a point just above the prop shaft, then makes a 90 degree turn up to the muffler, which is at the forward end of the port cockpit locker. The hose enters the side of the muffler and exits the top, with only a slight downhill run from the top of the muffler to the transom exit fitting. I have attached several photos showing the installation. I drew a horizontal pencil line on the port side of the engine compartment at the waterline level, which is approximately four inches below the fitting where the water enters the riser. Also note the photo showing the exhaust hose where I separated it from the riser exit. The water level in the hose is just about even with the bottom of the riser exit, pretty close to the waterline level. This worries me because it wouldn't be hard for the water to slosh up the riser and into the manifold in rough weather. My cylinders/valves don't show any evidence of this having happened in the past but I have often had difficulty getting the engine started after a rough sail with waves and significant heeling. Also, I'm concerned that the low loop prior to the muffler may be causing excessive back pressure. I would welcome any suggestions for improving my exhaust installation. I need new exhaust hose anyway.

[Don Moyer]

I understand your concern. Any time you have a "gully" in an exhaust line after water has been added, there is a theoretical potential for elevating exhaust back pressure. While it is difficult to quantify the amount of additional back pressure, you should note whether you have any "batching" of engine cooling water as it leaves the boat at your normal cruising power setting. While batching of the cooling water at idle is normal, at any RPM above idle, the flow of water out of the exhaust should be continuous.

Given your space restrictions, and since the level at which you discharge your exhaust and water behind the engine is more or less fixed, you might consider simply removing the muffler and connecting the two hoses with a pipe nipple. My guess is that the low point (or gully) in the system would muffle the sound sufficiently. The Catalina 27 fleet has no water lift muffler and there is no gully in the exhaust line to muffle the sound.

I'm wondering if the inlet and outlet of your muffler might be reversed. I would check to be sure there is an extension of the top fitting that extends down close to the bottom of the muffler. If it does not, I would think that the top fitting would be the inlet.

Don

[rgoff]

I have a '73 Ericson 27 and your exhaust setup is definitely not a factory one (based on what I have).

[raleighm]

Photos of stock Ericson 27 exhaust setup?

rgoff, do you happen to have any photos of your exhaust setup? I have a friend here with an Ericson 27 but he has a standpipe exhaust system and I don't think I want to go to the trouble to convert to that.

Thanks for your help.

Raleigh