Exhaust noise on Volvo AQ125/270 outdrive

[2stroke1971]

At low RPMs, there is no noise, but pretty early on in the throttle, it starts with the lawn mower sound... It sounds pretty loud under the engine hatch, but I dont think its coming from the manifold, its been put on recently with new gaskets, and I cant feel any puffs from the port areas.


By the end of the trip, there is some water in the bilge, not enough to trip the pump on though.

I know the exhaust bellows needs replacing, when I was running in a bucket, there was a little hot water dripping out of it. Could a leak down there in the bellows cause noise up in the engine compartment? I figured since that would be under water, it wouldnt, but Im not sure.

From what I can see of the pipe, it looks okay....do they ever rust thru? The pipe leading down and out the outdrive I mean. I would have thought anyway, that any leak under the hatch would be accompanied by some water also, but even at full throttle, I see no steady drips or anything.

Thanks in advance for any ideas or suggestions.

 

[captmello]

Re: Exhaust noise on Volvo AQ125/270 outdrive

I would agree, if the exhaust tube was leaky, you could expect to get some water leaking as well. You replaced the short bellows between the mani and exhaust tube in the engine compartment, right?

I ran a friends aq125 last fall and it seemed to be a loud runnig motor to begin with, much louder than my V8.

Water leak? well you've just got to track it down.

 

[PiratePast40]

Re: Exhaust noise on Volvo AQ125/270 outdrive

Since the exhaust manifold was recently replaced, might want to start there. Was it doing this right after the mainifold replacement or something that's come up recently? Either way, I'd be looking at the manifold again, especially around the #4 cylinder exhaust port. That's a known area for corrosion on those engines.

The exhaust boot outside the boat shouldn't have any affect on noise inside the doghouse. If that's leaking, it won't hurt anything, just get exhaust soot all over the back of the boat. When you get up on plane, it might be out of the water and be loud but that shouldn't affect engine compartment noise.

Like Captmello said, the water leak might be totally independant of the exhaust noise. Might want to double check all the water pipes, their gaskets, and the drain plugs. It's possible that it's the exhaust pipe but I'd check the o-ring at the transom shield also.

Hope it's something simple.

 

[bruceb58]

Re: Exhaust noise on Volvo AQ125/270 outdrive

or gimbal bearing are done.

No gimbal bearing on this kind of drive.

 

[2stroke1971]

Re: Exhaust noise on Volvo AQ125/270 outdrive

The more important bellows, the top one, is new. As far as I know, the only thing running thru the one thats bad is exhaust.

I saw a small drip from the lower part of the engine in the rear...that may be the source of the bilge water. Nothing major I imagine. I will track it down in time, not worried though. Lets just say that my old boat got water in the bilge also, and whats worse is my left foot was always in it.

I did have some damage to number 4 port, but there was some decent sealing surface left. I will retorque the manifold..

Also suspect is the pipe from the manifold to the outlet pipe. I did NOT replace it with a new one. Lets just say I improved upon some shady engineering that had been there before me. No water leaking, cant feel any leaks, but thats something I should replace I suppose.

If the bellows will not shut it up, I will wait on that, and try a new short pipe.

Thanks again guys!