Motor sounding loud

[TahoeQ4Pilot]

Took my baby out for probably the last time for the year after sitting for about 6 weeks, it was a nice mid-70 day in Central Texas. It was a nice run and everything went well, but for some reason it sounded much louder coming from under the engine cover while at WOT. I have a 2006 V6 Mercruiser I/O w/Alpha One, been out a couple of times a month since I bought it used in April, it wasnt this loud in the past.

I had it up in the 50mph range on the speedo, but about 4300 rpm range on the tach. I have not done anything different this time out, but did have a plug-in situation where the hull filled up after a rainstorm. Not enough to get water to the engine fluids, but about half-way up the motor. I could hear the motor prett loudly from underneath the engine cover and it was not like I heard before.

Could it be exhaust bellows related, or maybe exhaust gaskets? I gave it a good eyeball inspection, nothing seemed out of place. Thx.

 

[cr2k]

Re: Motor sounding loud

It is common for the exhaust bellows to come off one end or the other. Not an operating issue but it will sound louder.

Did, maybe, the water in the boat compromise the insulation on the cover?

 

[ENSIGN]

Re: Motor sounding loud

Start the engine and look for a leak! been working on these for almost fourty years,bellows are NOT supposed to come off.

 

[TahoeQ4Pilot]

Re: Motor sounding loud

I thought exhaust bellows myself, but heck if I could find anything that looked like an exhaust bellows on a 4.3L. I had it running and popped open the engine cover and looked all around, been tinkering on cars and GM products for 30 years, I am not sure what I thought was the exhaust manifold was actually the right thing.

Is there an esy check without pulling the motor?

 

[180shabah]

Re: Motor sounding loud

Exhaust manifold is in the exact same location as it would be on a car/truck. Stuck on the side of the head. The difference here is that they turn upward, not down like a car. Also, they are water jacketed so they are much larger/bulkier. After exiting upward the exhaust enters the elbow where it turns backward(slightly down) and enters the first "bellow", then into another cast piece that turns down into the second "bellow" then into the y-pipe and out through the drive.


Low waterflow from the seawater pump can also make the exhaust louder, as can a paranoid ear.......

 

[cr2k]

Re: Motor sounding loud

Since you didn't mention any water in the bilge I would not suspect one of the exhaust coupler hoses. But it could be. If the boat was ever run without cooling water they will burn form the inside out.

 

[ENSIGN]

Re: Motor sounding loud

Could also be a bad manifold to head gasket,try spraying some fogging oil down the carb and look for smoke around manifolds.

 

[zbnutcase]

Re: Motor sounding loud

I like the paranoid ear theroy...'nutcase

 

[TahoeQ4Pilot]

Re: Motor sounding loud

Since you didn't mention any water in the bilge I would not suspect one of the exhaust coupler hoses. But it could be. If the boat was ever run without cooling water they will burn form the inside out.

I had a whole thread on my newness stupidity starting the motor at the top of the ramp (it needed a jump start) and backing in down while it was idling. I figured I had been on borrowed time.

But I did have water in the bilge, no reason for it, no one got in and out. Small amounts, a couple of different runs of the bilge pump.

 

[Maclin]

Re: Motor sounding loud

What kind of noise is it,

a single high pressure puff in synch with the rpm like an exhaust manifold leak?

or a throatier sound like you hear from a car with a rusty worn-out muffler?

or is it more like the 4bbl bellow as the engine demands more air?

 

[Bondo]

Re: Motor sounding loud

I gave it a good eyeball inspection, nothing seemed out of place.
I had it running and popped open the engine cover and looked all around, been tinkering on cars and GM products for 30 years, I am not sure what I thought was the exhaust manifold was actually the right thing.

Ayuh,... There are some Manuals up in the Adults Only section of this forum,...
Go Read some, Look at the Pictures....

We can't help you Fix it, if you Don't know what We're talkin' about,... Educate yourself....

Then go follw the exhaust path with your Ears,+ Fingers, rather than a Eyeball inspection...

 

[TahoeQ4Pilot]

Re: Motor sounding loud

What kind of noise is it,

a single high pressure puff in synch with the rpm like an exhaust manifold leak?

or a throatier sound like you hear from a car with a rusty worn-out muffler?

or is it more like the 4bbl bellow as the engine demands more air?

It is more of the second. I actually thought my engine cover was up a bit and the engine bay sound was escaping.

 

[TahoeQ4Pilot]

Re: Motor sounding loud

Ayuh,... There are some Manuals up in the Adults Only section of this forum,...
Go Read some, Look at the Pictures....

We can't help you Fix it, if you Don't know what We're talkin' about,... Educate yourself....

Then go follw the exhaust path with your Ears,+ Fingers, rather than a Eyeball inspection...

Sorry, I was being tongue in cheek, but you are right. I did in fact look at what is the exhaust manifolds, but was surprised how they mount (upward, in relation to a car) and that they were so large (as explained above as being jacketed for water). I also touched it on a running engine, one that had been running for a bit at operating temperature, it was easy to touch, not too hot.

Gotcha on the inspection with hands, good point. It is the end of the boating season for me so I will take it in to the shop for winterization and have them replace a couple of things, bellows and impeller will be among them.

Its my first boat and I got it used and now know about things like bellows and impellers, something I wasnt smart enough to be aware of when I bought. I dont know if they have ever been changed, so I figure I might as well start next year from a known point.

Thanks all for the advice.

 

[Ohioriver]

Re: Motor sounding loud

Did you have your bimini top up when you were hearing the noise? My engine always sounds louder when im driving with it up. Its like it reflects the sound of the engine back into the boat.

 

[Knightgang]

Re: Motor sounding loud

Did you have your bimini top up when you were hearing the noise? My engine always sounds louder when im driving with it up. Its like it reflects the sound of the engine back into the boat.

The cooler air will do the sam thing...