Is engine cold start hissing sound normal?

[seilings]

Hi guys,
Maybe this is a stupid question, buy I want to know why.
When my engine cold start, it runs with some kind of hissing sound, when temperature reach 175, then the engine will become much quieter. This is more obvious if I open the engine compartment hood.
The engine runs perfect and no issue so fart, but is this cold start noise sounds normal?

Thanks in advance.

 

[Another retired guy]

Re: Is engine cold start hissing sound normal?

Hi. Maybe you could provide some details as to what sort of engine you have??
Hissing sound isn't normal

 

[seilings]

Re: Is engine cold start hissing sound normal?

Hi. Maybe you could provide some details as to what sort of engine you have??
Hissing sound isn't normal

Thank you for your reply, my engine is Mercruiser 4.3L with 2 barrel carburetor. S/N: OW629061

I am not sure how to describe the noise, sounds like hissing which I still feel normal, I though it is normal engine noise comes from the belt or any sort of rotating parts, but what makes me curious is when the engine temp approach 175, the noise goes away, and the engine become really quiet, that when you are on water, the only noise I can hear is the exhaust.

 

[Another retired guy]

Re: Is engine cold start hissing sound normal?

Kinda hard to say what it is without hearing it
Only thing I can think of is "maybe" a vacuum leak somewhere that seals off as engine warms up and metal expands. If you're not experiencing any starting, running, or temperature problems then just keep an eye ( ear ) on it. If it gets worse in any way, then some troubleshooting may be required.

 

[dccordell]

Re: Is engine cold start hissing sound normal?

I have no experience with the 4.3L, but...

Does it have an electric choke? My engine has a hissing sound at the carb until the choke opens after a couple minutes...

 

[Fun Times]

Re: Is engine cold start hissing sound normal?

Since he has a TKS carburetor the hissing noise is considered normal when cold. The noise should be gone by 154 degrees.

Your hearing the enrichment module system warm up.

Item number 1, http://www.mercruiserparts.com/Show...11540.png&inbr=11741&bnbr=80&bdesc=Carburetor

 

[500dollar744ti]

Re: Is engine cold start hissing sound normal?

^^^ you telling me that a TKS carb has a fuel injector in it? haha, learn something new every day.