Mystery location of blue drain plugs

Debt-icated

Debt-icated

Member
Apr 11, 2007
115
Spokane, WA
Boat Info
'10 310 Sundancer
Tow Vehicle: '21 F-250 Powerstroke
Engines
Twin 5.0L DTS
Bravo III
Hi all,

Feeling a bit silly, but for the life of me I cannot figure out where the 4th blue drain plug gets inserted on the engines. (I didn't winterize.) For reference, I have twin raw water cooled 5.0 MPI DTS Bravo III. I found 3 of the locations on each engine, thermostat housing, the multiport drain housing, the seawater pump. I thought the 4th plug would go onto the cool fuel module, but it appears my boat does not have the drain plug version on that module, (assuming it would be located on the bottom of the front side of the module.) I've scoured the manuals and even the online parts diagrams. I'm stumped. Any ideas?

Thanks.
 
Bottom of both ex. manifolds, sometimes there's 1 on the large hose that connects to the circulating pump front of engine
 
Mine has 2 on the raw water pumps... one right above the other.
 
Appreciate the replies. I'm almost 100% certain that my seawater pump only has 1 drain plug. At least, that's what's indicated on the parts drawing from the Mercury website when I input the engine serial number. I also do not believe I have drain plugs on the exhaust manifolds. I will check over all suggested locations again tonight after work. Thanks everyone.
 
Start it up on the hose. Put the blue plug in the hole that is leaking. :)

Do you still have the original raw water pump? If it was changed at some point, it might be the style with two plugs.

FYI, a better practice is to have your shop fill the block/manifolds with non-tox AF after draining (which means putting the blue plugs right back in). The AF helps to keep away internal rust/corrosion while at the same time eliminating any small pockets of water that might still remain.
 
Thanks LD,

I may have to start it and do as you say. My Sea Ray dealer is the only mechanic that has done any service on any of the boats I have had including winterizations. They have always taken the plugs out. Your method seems better, I wonder why they don't do that.
 
as Lazy Daze and others suggested I found I do have to drain ports on my sea water pumps. I appreciate the help! Now, I just need summer to hurry up and arrive.
 
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