Cool Fuel Raw Water Plug

M

mawyatt

New Member
Dec 13, 2007
1,001
Clearwater, Fl
Boat Info
2008 Sundancer 38DA
Engines
8.1L Mercruisers
We have the Merc 8.1L and the cool fuel module raw water plug snapped off. This is the blue plastic plug used for draining water when winterizing. I checked the other engine and the plug was stuck and snapped off too. It seems the plug with o-ring was placed on the cool rule module before the module paint was dry, this caused the o-ring to not seat properly and allow salt water to weep out over the years. When I looked closely I noted the o-ring was stuck to the module wall like it was glued in!! So I have to replace the plug and o-rings or maybe just a brass plug.

I was thinking of drilling out the remaining plastic from the plug and using a tap to extract the remaining plastic left after the drilling. Anyone know the thread size I would need for the tap? Also where to get the replacement plastic plugs and o-rings if I decide to just replace them instead of the brass plug?

Thanks,

Mike
 
Funny, I just mentioned this in another thread, so I'm copying and pasting this... For what it's worth, for stubborn blue plugs, I keep a 1/2" deep socket in my tool box that I have cut (grinder) two slots into. The slots are on opposite sides to allow it to slip over the "wings" of the plug. Then I can use a stubby socket wrench and appropriate extensions, if needed.

This will usually still work, even if the wings/ears are busted off.

I believe that fuel module is painted AFTER the plugs are put in. It sounds like this is the first time these plugs have been removed? That would explain why the o-ring is sticking - it's been there a long time. Sometimes they even stick a little after only one season. I use a dentist-type pick to remove them.

I believe the thread size is 1/2"-13 straight thread. You can get them readily at any Merc dealer. Common item. Buy a few extra and keep them in your onboard tool box.
 
Dennis, you beat me by seconds!
 
JimG said:
Dennis, you beat me by seconds!
Click to expand...

It's funny how that works, sometimes, isn't it? Here we are hundreds of miles away from each other, but doing the same thing as each other at the same time.... When we should be working.... :smt001
 
Thanks guys!!! Good timing!! The plugs both broke off leaving nothing to hold on too, and both began leaking. Guess I'll get a 1/2"-13 thread tap and try and clean the threads out.
 
Usually, just the ears broke off. If it broke off flush, that's strange. They really must have been in there quite a while. There might be some other ideas, based on how it broke off and whether or not you feel comfortable removing the whole module... it would be a whole lot easier to work on it at your workbench.
 
Agree with Dennis. Remove the whole thing if you can. I'd replace the blue plastic with bronze and check the hose fittings. At some point they were changed to a more robust fitting from the POS fittings that were in there. Additionally, that era fuel cooler was prone to corrosion issues. It wasn't one of Merc's finer moments. DAMHIK!!!!!$$$$$:wow::smt089:wow:$$$$$!!!!!
 
Are there reports of these units leaking water? I have water that collects in my bilge when running.
 
My dealer had plenty of those blue plugs. They are always breaking or getting dropped and lost in the bilge area.
 
I bought six at the local Merc shop. Surprised that they are $6 each.
 
Mark,

Don't have a picture but it's easy to spot the blue plug. It sits on the bottom of the cool fuel module and faces aft on our boat (V Drives). Its there for draining the raw water when winterizing, we are in Florida and don't need to winterize...so the plugs haven't bee removed since the boat was built in 2007.
 
Is anyone replacing these with something better? I had one breakoff about 3 months ago, replaced on both engines and yesterday the head of one was laying on bilge.
 
625-4289.jpg


Stainless Steel plugs. $5.59 ea or $24.99 for 5
https://www.hardin-marine.com/vsearch.aspx?SearchTerm=drain plugs

Have used them on last 3 engines and never a problem
 
When I had my 340 I had the same plug in that cool fuel module break when I was on a cruise trip away from home port. spitting water everywhere when engine was on. Was not going to travel with it like that. So I shoved a bunch of tooth picks in there and it stopped leaking. Eventually replaced with new plug.
 
Brother in Law had one snap off after hitting t while in the bilge doing other work. As we were in the middle of the Chesapeake, needed to repair. Was able to gently tap a torx socket into it and back it out. Worked well for this one.
 
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