Noise in Y pipe

[Johnson110]

Hi, Question I have 1995 5.7 Mercruiser with a noise like something is knocking around in the y pipe, if I put my hand on the pipe I can feel the noise, I changed the exhaust flapper on both sides, the old ones were still complete when I removed them. I had a new transome shield put on 2 seasons ago, The engine runs fine, any ideas ?

 

[Don S]

Re: Noise in Y pipe

Rubber worn/burned off the exhaust flappers. Pull the elbows and have a look.

 

[Johnson110]

Re: Noise in Y pipe

Thanks for the reply, I did pull the riser hose off the right side Flapper looked fine ? Anything else to check?

 

[Don S]

Re: Noise in Y pipe

There is nothing else in the Y pipes other than the flappers. Are you sure your not hearing a backfire from the engine?

 

[Johnson110]

Re: Noise in Y pipe

Thanks again, I am going to listen to the noise again, I used a screwdriver very carefully in the engine and the noise seemed to be in the Y pipe, The noise does not soung like it is coming from the engine, the noise is coming from the back of the engine by the y pipe or transom.

 

[Don S]

Re: Noise in Y pipe

You can hear it and feel it .............. we can't. We can only see what you type.

 

[svxtech]

Re: Noise in Y pipe

exhaust leak? bellows or manifold...?

 

[cr2k]

Re: Noise in Y pipe

Usually the things that get into the Y pipe are parts of the flappers. If someone before you replaced them and there is a pin in there it will eventually wear through the pipe causing it to leak water and exhaust in to the bilge. The pin is SS and the pipe is aluminum so guess which wear which. You may be able to see anything there by pulling the drive and looking up the exhaust.

 

[Johnson110]

Re: Noise in Y pipe

Thanks, I am going to pull the boat out of the water real soon, I will pull the drive and inspect, I know that a noise in an engine/outdrive is tough to explain and a pain to diagnose!

 

[jersigsel22]

Re: Noise in Y pipe

You say Y pipe. Is it switchable exhaust??? is it a constant tapping/ticking noise or is it random(a tap here and their)?

 

[Johnson110]

Re: Noise in Y pipe

The noise is a constant tapping coming from y pipe, I used a screwdriver one end to my ear other to y pipe, it sounds like it comming from the pipe, I put the screwdriver to the oil pan and did not hear the noise, Switchable exhaust no!

 

[paultjohnson]

Re: Noise in Y pipe

Is the constant tapping in time in an even rhythm, or random? Does it seem to decrease with increased RPMs? I can hear my flappers at idle , its somewhat random, and it decreases as the RPMs pick up as the exhaust pressure holds 'em open. If its on an even rhythm. I would suspect valve train issues, A loose rocker arm causing lifter tick, tick, tick or tap, tap, tap, for instance. The best home stethoscope I have come across is a 3 ft chunk of hose from a wet dry vac. It lays flush on whatever u suspect is making noise [ for the most part] as well as easy to put to your ear.