Winterizing a Closed Cooling System - 260 Sundancer 350 MPI

SARBlade

New Member
Sep 28, 2021
16
West Coast BC
Boat Info
2005 Sea Ray Sundancer 260
Engines
350 MAG MPI Mercruiser Bravo III
Hi All, I've searched the winterizing section here and all is great info, but soooo many different systems and not everyone is clear on what system they have or what they are doing. As I sauy in my title I have a Mercruiser 350 MAG MPI, its in a 2005 Sundancer 260. I have a closed system, the engine is cooled with its own anti-freeze, I tested it, its good to below -40 degrees. I have a single point drain system, I followed the Mercruiser manual and drained this with the bicycle tire air pump. Then I pulled the blue drain plugs on starboard and port side, poked them with a small screwdriver to clear contamination and get out anymore water. I also drained and cleaned the main sea water strainer. Now I want to run the anit-freeze through the muffs on the Bravo III leg as stated by others here with a small submersible pump and a 5 gallon pail. However, and this is where I'm confused with the system. My raw sea water enters th cooling system throught the bottom of the hull and the Bravo III. If I leave the seacock closed to the sea strainer, then the anit-freeze should only enter through the muffs, is this enough, or am I missing something here? I do have one of those plunger things that I can cover the hull port with and it extends to the ground to be held in place. Do I need to use it? Thanks to anyone that can point me in the right direction.
 
I had that setup and mine wouldn't pull from the drive. I taped the pickup holes on the drive and poured a couple gallons of AF into the strainer with motor running
 
Your suggested method could work, but as mentioned, if there is any small air leak it might not develop suction. I would get some helpers, use the pump on the leg, and have another pouring into the strainer suction line to the motor. Seaflush.com has a tool, and if you look at it you can figure out your own version.
 
Thanks for the replies, I looked at the system more closely today, and the large hose from the seacock through a strainer says in the manual that it is for the generator, however, it is not, it goes from the sea strainer to under the block to the water pump on the engine. From there it goes into the system to cool the power steering, engine oil, exhaust manifolds and out through the leg.
halfclosedsystem.png

So I think according to this picture, I have this system with the optional thru hull pickup. So I guess, I will close the sea cock for the hull pickup and add antifreeze as suggested above through the sea strainer and the leg with muffs. I'll advise how it goes.
 

Forum statistics

Threads
112,945
Messages
1,422,731
Members
60,927
Latest member
Jaguar65
Back
Top