Different exhaust noise ??

[Tom Schlagel]

I noticed this year that our Yanmar 3JH2E (38 hp) seems to be making a different exhaust sound from previous years. The sound is a wuh-wuh-wuh. It seems that water is coming out fine. I felt the exhaust water after powering for 4 hours and it was warm so I assumed that the engine wasn't running hot. I replaced the impeller this spring along with my usual filter changes and oil and tranny fluid. I replace the oil and filter twice a year. I felt the mixing elbow underway and it was warm so I assume it is working ok. Could the mixing elbow be partially clogged thereby affecting the amount of water that streams through the exhaust? We bought the boat new in 1994 and have never replaced or serviced the mixing elbow. Any ideas??

 

[Gordon Torresen]

Exhaust sound

When the sound of the exhaust changes, its time to look for the reason. Usually it is a change in the amount of cooling water that gets into the flow of gasses. You state that the water coming out looks normal and that the impeller was recently changed. (any broken blades on the old one?)  It doesn't take much of the area of the exhaust path to let the water by. If the sound has changed, something in the system has changed. There is a good possibility that the mixing elbow has been restricted after six years in salt water. Its time to check it anyway. If that's not the cure, check the rest of the exhaust tubing. Sometimes the interior of the tube can start to delaminate and "flaps" are formed that impede the exhaust flow. Sometimes its and anchor that has been placed on top of the exhaust hose. I'd like to know what you find. Its good to hear from someone who pays attention to the sound of an engine.

 

[steven f]

water flow

I have a H33 with a Westerbeke 21A (24hp). Last year I did a simple change of my impeller and notice my exaust noise was different. I later noticed that she was running slightly warmer than before. I reassessed my impeller than started from scratch. I started at the sea-strainer and made sure water was flowing freely from it. I followed all the water lines to EVERY part and made sure water was flowing freely. To make a long story short, it was my heat exchanger. It was so clogged that the amount of water was restriced. I also removed the elbow before removing the exchanger but it was beautiful. I finally replaced the exchanger and after several days of crawling in the tight engine compartment and smashing nearly every knuckle. Now all is well. I recently took a trip that had us motoring for 10 hours on one night to try outrunning a storm. She ran like a top. I truly hope your problem is easier than the heat exchanger. I only tell you this story because if you think your boat's exause noise is different than it probably is, find out why if you can.