Looking for assist with locating raw water exhaust jacket drain plugs on my 454 MAG MPI Horizon

[msballin]

I've tried searching many forums for this information, so my apologies if this is info is already posted. I'd like to drain the raw water from my exhaust until I have a chance to run the pink through the system. Thanks in advance as always.

Best,

Michael

 

[John E3]

If this is the same engine as mine, as the title states, there are a number of locations for drains.
Depending on what exhaust manifolds you have, there could be brass plugs (3) on the bottom, plus a blue drain plug in the hose elbow.
There should also be a blue drain plug in the outlet hose from the sea water pump, and another on one end of the fuel cooler, in the hose.
The inlet hose to the SW pump also holds water, so I disconnect this from the strainer and let it drain as well. And of course the strainer has a plug, and don't forget to open the seacock and let it drain.
If in doubt about where to find them, start at the strainer and follow the hose - Seawater pump, trans oil cooler, fuel cooler, engine oil cooler, heat exchanger, where it exits to 2 hoses one to each exhaust manifold.
This should be sufficient to drain the water, and antifreeze shouldn't be needed. But, proceed at your own risk.

I have a post about manifolds without drain plugs and am suspicious about how well they drain. There is no blue plug in the elbow either. Mercruiser says they self drain.... I pulled the hose and got lots of water out.