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Thread: OIL PLUG modification

  1. #1
    Junior Member Bart's Avatar
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    OIL PLUG modification

    I have been looking at a few different ways to put a temp sensor in the oil pan..
    I remember reading a while back, where Corky did something that worked , but it is hard to find the post to see what he did...all I remember he had some fun with the threads.

    knowing that the oil plug threads are just a little different, I stopped by the local boat repair shop, and found the correct flare nut that fit the oil plug threads, it was a BTX-B-8 Nut 37 Flare 1/2 in. JIC with 3/4-16 UN/UNF-2B Thread -

    it is handy to have a something to reference when turning threads on the lathe.. because once the piece is removed, it can get entertaining if the threads are not with in spec...a 2 dollar thread nut is a small price to pay.
    I put in an order for some 1 in. hex stock, but all I had on hand at the moment is some 1" aluminum hex stock, so I thought I would give it a whirl and see how it turned out... I threaded the inner dia. for a 1/8" npt
    there are a few different styles of temp sensors, the one that I had on hand the threads are in the middle. I would like one where the threads will let the probe go further into the oil..
    kind of wondering if I should use brass hex or steel, or just keep the aluminum one...for the mod? any ideas for either?

    an other thought, would it really matter where I would get an better temp. at the edge of the pan, or a couple of inches in. or am I just over thinking again...
    I could always make a custom sensor to the length I wanted..

    another thought, where I will lose the magnet, I could glue a strong magnet on the outside bottom of the pan to attract any metal partials

    Also just putting it out there, if anyone would something similar. let me know. and I will turn one out.
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  2. #2
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    Re: OIL PLUG modification

    Will this modified plug be the only drain point available for oil changes? If so, I recommend steel or brass, instead of aluminum. Aluminum, being soft, has a greater chance of galling and locking up in the steel pan threads. Do be careful with how far you insert your sensor. You could run into interference from the swinging crank, and the sensor will lose the battle.
    OK.....looking at the pics a second time, it appears that the sensor will be located close to a lower corner of the sump. It's inlikely you'll have any clearance problems with the crank.

    Roger
    Last edited by GTS225; 07-27-2020 at 12:12 PM.

  3. #3
    Super Moderator Corky's Avatar
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    Re: OIL PLUG modification

    Good point Roger and the aluminum could very well end up loose with frequent oil changes...Bart going off memory, the original oil plug has straight threads and rely on the fiber washer for sealing duty...The brass plug I bought had tapered threads and I ended up using a die to change the threads to a standard thread..I'm sure you've already run into this but you have to watch how far the sending unit goes into the 084 pan there isn't much room after the plug is installed..It appears the front plug might have a touch more room with the taper of the pan..
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    Last edited by Corky; 07-27-2020 at 06:44 PM.

    Aluminum .120 14' X 76" hull
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  4. #4
    Junior Member Bart's Avatar
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    Re: OIL PLUG modification

    those are some good ideas, I just turned the one out of aluminum, because I had that on hand, and was wanting to see what the side wall was with a 1/8" pipe thread in it. I was thinking of tuning one out of a bolt. but to get the 3/4" dia. for the threads, the bolt head was 1-1/4, so it was back to 1" hex stock
    looking at what is available. 1018 steel or brass. Brass is twice the cost, but leaves a good machine finish. 1018 steel is not so easy in leaving a good finish. on the small lathes.
    also I came across some 420/430 stainless bar, which is machinable. but still leaning towards the brass.

    that is also another good point. as to how long the probe can be. I measured the depth in the drain well in the back corner of the oil pan, from the face where the gasket meets, to the edge of the well, is 1.42 inches, so there is a little wiggle room of almost 7/8" into the oil..
    looking at the picture, that should be more than enough...

    I am thinking at the rear of the pan, the oil would be hotter, due to a couple of reasons. it is right below the relief drain pipe from the oil pump. so there is more circulation, in that corner, and being on the leeward side of the air flow, the heat will not dissipate as quick, like at the front of the pan. it might be only 10 degrees, but that is something I will be looking at with the temp gun.
    all in all, I am liking the pitch of the threads I turned out. it matches the JIC pitch, and on the lathe it is just a time thing to turn them out.
    figure with the few gasket kits I have purchased,there should be an gasket for the oil plug included.
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  5. #5
    Junior Member Bart's Avatar
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    Re: OIL PLUG modification

    the 1" SS 420 hex stock came in today, ended up making 2, I was trying for another 1/4 turn with the plug tap. and now I need to remove the broken part. after fiddling with it for a while. It was simpler at the moment to turn out another one.
    the only thing I changed is putting a 1/16" landing on the inside shoulder, to give the hex a little distance from the tank.

    I like it. the oil temp gauge only hangs out past it, by 3/8 of an inch.
    now I just need to drain the oil and install.

    if anyone would like one similar to this let me know, and I will see what I can do...
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  6. #6
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    Re: OIL PLUG modification

    Ain't it great having a metal lathe just waiting for you to turn something out as needed?

    Roger

  7. #7
    Super Moderator Corky's Avatar
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    Re: OIL PLUG modification

    Nice work Bart...PM me and we'll work out the details...I could use one for my other 084 engine...

    Aluminum .120 14' X 76" hull
    Teledyne 4a084-4 engine
    Circle S 1.69:1 reduction
    67" Whirlwind "Razor X" prop



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