Hissing noise on Volvo Penta GI E 8.1

[James]

I changed the exhaust manifolds and elbows. All tight no leaks at least that I can see for now. I kept the engine hatch partially open so I could inspect for any leaks under load. I noticed an annoying hissing noise when throttling up between certain RPM range and it stops hissing at higher RPM and not at all at WOT. Because the air management is only a flame arrestor, is that hissing noise normal? BTW new fuel cell and it passes pressure tests so not coming from there. Thanks for responses in advance!

[AsLan7]

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Our 8.1GI made a hissing noise when running while we owned it. I wouldn’t call it annoying but it’s normal for that engine.
Have you tried turning the stereo up? It seems to fade away the louder we cranked our tunes.

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[James]

Haha! Yeah, turn up the stereo is a great idea! Well, with the engine hatch closed, it is much less noticeable. It just doesn't seem right to be that loud.

[Big Block Power]

I bet if you put her in the bow the hissing noises move up frt

[Big Block Power]

Normal. I added the air intake shield on mine and pretty much eliminated it. Along with a iac filter. And a new engine cover. I wanted blue and this is as close as I could get.

[James]

Hum, now that's interesting! A Cobalt air box? Also, that IAC muffler looks like it is for Mercruiser, not sure it will work on this here Volvo. Any idea where I can obtain that air box? A Cobalt prat?

Thank you

James

[Big Block Power]

Hum, now that's interesting! A Cobalt air box? Also, that IAC muffler looks like it is for Mercruiser, not sure it will work on this here Volvo. Any idea where I can obtain that air box? A Cobalt prat?

Thank you

James

Yes the throttle bodies are the same. I have it in mine. Good look finding the cover. I think they started using it on 2010. Volvo said it's not there part and cobalt says it's not there part plus of its past 7 years you can't get out anyways. I got lucky and found it on ebay from a left over new stock.

[cmattj]

Yes I had two whistles on our 282 but very slight.

Let’s insure your hatch seals are contacting and trying a new IAc muffler as BB mentioned. it’s difficult to cure completely but you can lessen it.

Some here with Merc 8.1 can go with a K&N and about eliminate it.

Or buzz her up to 3600 rpm and it will stop

[James]

Thank you both. Yeah since the throttle bodies are the same I'll go ahead and put that muffler in there. And I do adjust the throttle to a point where it is not annoying my sensitive ears. Can also solve with a captains call install!

[Big Block Power]

Thank you both. Yeah since the throttle bodies are the same I'll go ahead and put that muffler in there. And I do adjust the throttle to a point where it is not annoying my sensitive ears. Can also solve with a captains call install!

And full throttle