9/16 allen wrench tool for Mercruiser brass plug

S

Stephen

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I ran into a challenge as I was getting my new Mercruiser 350 manifolds ready for installation. They came with four large plugs; two installed in the top and two loose in the box for the bottom. There is also a third hole in the bottom for the water inlet from the thermostat housing. I guess they don't install the bottom plugs and water inlet because they are in different places for different applications.

Anyway, the plugs are installed via a 9/16 allen wrench, which I don't have. Not finding one local to me I thought I'd have to either buy a whole set for $40+ or wait days for an on-line purchase for just the 9/16 for around $10. Neither was really appealing for a one-time use tool (and I have way too many one-time use tools already).

So I made my own tool. I bought a bolt with a 9/16 head, two washers, and two nuts. I put the washers on first to keep the nuts from chewing into the brass plug leaving sharp edges to cut myself on, and then the two nuts to use with a deep socket. Worked like a charm, was available local, and cost under a buck. I just thought I'd share for those who run into the same problem.
 
That's the same method used to remove studs in an engine and elsewhere. The double nuts lock into each other allowing the stud to be removed. Great info. Thanks for sharing that method/secret with everyone. I'm sure it will come in handy when others are working on their engine's manifolds. Hy. (PS. That's meant as a compliment, not as sarcasm!)
 
Yeah, I know about the double-nut method for studs. But this is the first time I've used the head of a bolt as a hex wrench. Frankly, the design of the plug is annoying. There is no reason why they couldn't have simply used a half-inch square (male or female) for these like the third one on top.
 
Search "9/16 hex driver" on Amazon, produced these for $10
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I remember trying to part the plugs out of some old MerC manifolds. Whatever the drive size was, and I forget, they would not budge. Easier to install...
 
yup, what jd showed is how my tool box got soo heavy. all those little specialty tools that make jobs easier.
 
I spent 60 years gathering and using various tools to fix our cars, our boat, and our house. When we 'downsized' two and a half years ago, I found myself with a tool shed and garage filled with tools I could no longer use. The co-op doesn't allow me to do anything more than paint; the cars are relatively new and are covered by warranties. I can still fix and maintain things on our boat, though it's getting increasingly more difficult to put my body into positions to do the work. Luckily, my tools are in our daughter's and son-in-law's garage about a mile away so my tools are nearby. Mostly, I can look at them and remember the jobs I used to do. I do have a set of hex-head sockets (1/2" and 3/8" drives) and have used them on previous boat and car engines; but before I could afford to buy them, I used a double-nutted bolt. I tried to sell them when we moved, but most of them have no resale value. Someday, I'll give them to some young man or woman first starting out to be a mechanic/technician. Hy
 
Hy: I'm in the same position. After decades of fixing everything i'm pretty limited these days. I donated most of my tools to the local high school automotive shop. Except those i could use in the condo.
 
quote:
Originally posted by Stephen

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Excellent easy work-around, Stephen. Thanks for posting as I don't think that one would have occurred to me, and is now added to the bag of tricks.
But those plugs on my blue engine exhaust parts have 1/2" square drive plugs so I'm covered for now.
 
That *is* a useful tip! If I didn't have the allen key, I probably would have gone to harbor freight to see if I could pick up a cheap set that had the right size, but even that takes time, and when you're working on a boat the last thing you want to do is stop working to go buy tools! Using a bolt with a pair of nuts is quite clever and would easily be good enough to put a couple drain plugs in.

Cool!

Adam
 
Harbor Freight doesn't carry them (at least not easily found on their internet catalog). Lowes/Home Depot don't sell them. The only place I found it available was Sears, and my local store had a peg on the wall where they should have been. But since they only carry one of anything, it wasn't there. At $40 for the set of four, I'm glad it wasn't there because I would have likely bought it. Amazon was at least a two day wait. It was pure luck that I thought of it at all because I was only comparing the plug against some bolts I had because I couldn't be sure if it was 9/16 or 5/8. Then the gears started working in my head.

Sandy, I went down to my boat today and sure enough, the old ones are 1/2" square plugs.

Oh, and another thing to get you mad, AC MR43T marine plugs are now made in China!
 
Regarding the plugs - we ended up going with NKG the last time...

Adam
 
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