Mercruiser 4.3 I/O Exhaust mixed in with coolant discharge

[swh03]

Is there anyone that can diagnose this symptom for me? I have a 4.3L mercruiser I/O on a 2000 maxxum 18' bowrider. Runs well, but i have noticed while flushing the coolant system that exhaust seems to be mixed in with the freshwater being discharged. Is this normal? There seems to be two discharge points, one on the port side of the drive unit and one on the starboard side. The starboard side is the one that has the exhaust mixed in, while the port side is very clean. Also, the port side discharges about 1/4 the flow and is not nearly as warm as the starboard discharge. I would expect both discharges to be similar. Any help would be appreciated.<br />Thanks,<br />Scott

 

[rabidfish]

Re: Mercruiser 4.3 I/O Exhaust mixed in with coolant discharge

It's all normal...

 

[Don S]

Re: Mercruiser 4.3 I/O Exhaust mixed in with coolant discharge

Those are idle reliefs in the transom shield, your system is 100% NORMAL.

 

[swh03]

Re: Mercruiser 4.3 I/O Exhaust mixed in with coolant discharge

thanks for the response guys! I wasn't expecting good news on this one.

 

[swh03]

Re: Mercruiser 4.3 I/O Exhaust mixed in with coolant discharge

I was trying to research the idle reliefs you were talking about, but couldn't find anything...could you elaborate on how that system works? The coolant system diagram in the manual doesnt' show much.<br /><br />Thanks

 

[Don S]

Re: Mercruiser 4.3 I/O Exhaust mixed in with coolant discharge

All the idle reliefs are for is to reduce back pressure on the exhaust at idle, at higher rpms, most of the exhaust goes out through the prop.

 

[outboardguy]

Re: Mercruiser 4.3 I/O Exhaust mixed in with coolant discharge

The idle reliefs also act as an exhaust drain so you don't freeze/crack the y-pipe with trapped water from when the drive is trailered coming out of the water.Also if all of your exhaust came out of your prop at all times you wouldn't be able to reverse with much efficiency due the prop sucking exhaust gases in and ventilating the prop