Stupid exhaust question

[fixb52s]

Great day so far. I got my 3.0 running, and it really seems to be in great shape! I guess the carb build went well and I got it together right and the dwell and timing was spot on. Not bad for someone who has not installed points in years! Getting the almost new dwell meter and timing light from my BIL was a good thing, and I am glad I hung onto it for the past 4 years.​

I did panic though when I saw water and exhaust coming from the transom mount. When I last ran it, the exhaust bellows was gone so I didn't worry, but I ASSUMED that with the new bellows on, all the water and exhaust would come from the prop. Looking at it, it looks like there are ports on both sides and the exhaust is suppose to come out there. And yes, some water and exhaust was also coming from the prop.​

Remember, this is my first I/O so I am still learning it (even though I am old hat to engines). Is there a reason for the exhaust bellows AND these ports? I am only trying to learn the hows and whys, and this site is a goldmine of info. Thanks!​

 

[friendly_jacek]

Re: Stupid exhaust question

This is normal in 3.0. Don't ask me why as I'm a noob myself.

 

[erikgreen]

Re: Stupid exhaust question

This is normal for most I/O boats. The holes at the transom the water and exhaust come out are called "relief holes" and they're there because at idle speeds the motor would run unevenly without an easier place to push out exhaust than the prop hub, which is 3 feet under the water's surface.

At speeds higher than idle most of the water/exhaust comes out the prop hub.

Erik

 

[Bondo]

Re: Stupid exhaust question

Ayuh,.....

As noted by Erik,.... Those are the Idle Relief Ports......

Perfectly Normal.....

 

[180shabah]

Re: Stupid exhaust question

Remember, this is my first I/O so I am still learning it (even though I am old hat to engines). Is there a reason for the exhaust bellows AND these ports? I am only trying to learn the hows and whys, and this site is a goldmine of info. Thanks!​

And for the second part of that question, the bellows.

When the boat is running on plane there is a low pressure area created behind the propeller, which actually helps to draw the exhaust out of the engine, through the bellows. There is very little passing through the ports until you slow down and the engine is now trying to push the exhaust down 3' to the prop.

Bottom line - they carry different amounts of exhaust at differnt times.