Muffler going bad?

[Seattle Scott]

I've had boat 3 years, with a Yanmar 4JHE (well its a 4 something for sure) put about 300 hours on engine for a total of around 1500 hours. I have noticed the exhaust sound out the stern has gotten louder, more sharp or less muffled. I have good flow on the raw water. How do I figure out if muffler needs replacing? As to the muffler I have, all I know is it is painted blue as in " I have no clue"

 

[Fred Ficarra]

Scott, I'm sure it's fiberglass, right?

The symptom you describe is a LACK of water from the raw water pump. Are you sure about the flow? Maybe if you changed the trim recently, it might raise the exhaust from the water and make it louder. Might.

 

[Wayne]

Lacking water

Get a marine mechanic to check the water pump Scott, I know when I have been a long sail the water pump takes a while to get the pressure up and the exhaust is must louder until the water pressure is right.

 

[Bob]

Water flow

Scott, It think everyone is on the right track. I noticed a louder noise from the exhaust on a cruise recently. I had picked up some seaweed in the raw water strainer, it has also gotten lodged in the 90 degree fitting coming into it. The water flow out of the back seemed ok at the time but the sound was different. You may also want to check the intake under the boat for obstructions.

 

[Marc]

When my Volvo

28 HP got louder, I noticed a slight less amount of water exhaust. I diconnected the raw water hose after the pump and got a gush. I then removed the exhaust elbow to find it clogged with carbon. Water was being restricted.The engine also had the sound of an air cooled engine (louder)IHTH,MArc

 

[JC on Bainbridge]

Marc maybe right

Yes, Check your elbow. No, no, no, not the one one your arm. I just replaced mine a few weeks ago. The engine was often overheating at high rpm, and lot less water coming out at idle, and had a hollow sound to it.Marine muffler usually lasts quite a few years. You said you currently have a good water flow, is it during idle, or high rpm?

 

[Seattle Scott]

I'll run through the raw water system

but without quantifying, I'd say raw water just dumps heaps and heaps when idling at the dock. I'll take off and check the elbow when the weather gets bad, just to say I did.Thanks. I just hate engine noise.