What do you use to seal block halvles? permatex aviation sealant ok to use?

Home Forum Ask A Member What do you use to seal block halvles? permatex aviation sealant ok to use?

This topic contains 7 replies, has 6 voices, and was last updated by outboardnut outboardnut 2 days, 2 hours ago.

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  • outboardnut
    outboardnut
    US Member - 1 Year
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    chris-p
    Canada Member - 1 Year
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    Topics: 154
    #158841

    No that will not work. Must be anaerobic.

    Loctite 515 or 518 are off the shelf options.

    The Permatex equivalents are 51531 or 51813

    The OEM Product is Gel Seal II 324073 or 767244

    I have a funny feeling this is all the same stuff in different packaging! (The 518/51813 and Gel Seal)

    bobw
    bobw
    US Member - 1 Year
    Replies: 289
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    #158855

    Although I have almost always seen an anaerobic sealer recommended for sealing crankcase halves, I’ve also seen folks recommending and using Permatex Motoseal gasket maker. While rebuilding one of my motors, I contacted the Permatex tech support group and inquired about their anaerobic sealant or their Motoseal product for use in 2-cycle crankcases. They actually recommended the Motoseal. I’m certainly no expert, but I’d like to hear other’s thoughts on this. Here’s the Motoseal link. Sounds like it would work?

    https://www.permatex.com/products/uncategorized/permatex-motoseal-1-ultimate-gasket-maker-grey/

    Bob

    1954 Johnson CD-11
    1958 Johnson QD-19
    1972 Evinrude 25202


    chris-p
    Canada Member - 1 Year
    Replies: 2425
    Topics: 154
    #158932

    Typical Situations may be fine, I have a feeling it has “fillers” in it. Not good for crankcase halves. You do not want ANY hardening of the material until the halves are torqued to avoid air leaks. Probably work fine on a gearcase though? Not sure, I have personally never tried it.

    My 2 cents is anaerobic sealers are not hard to find, so why not just use them as per OEM recommendation? Not sure why you would want to use anything else really, that’s just me though.


    phil
    US Member - 1 Year
    Replies: 46
    Topics: 3
    #159076

    What make/year is the engine?


    zul8tr
    US Member - 2 Years
    Replies: 146
    Topics: 4
    #159468

    I have seen some use the Permatex No3 on the split cases you note but i wouldn’t use it – too thick.

    On the split crank case 2 strokes I use Permatex anaerobic 51813 (Locktit 518 equivalent), it is a red gel. Important to note the blocks on split Crank Case engines are machined with the halves bolted together without any sealant. Therefore any sealant that is too thick will upset the dimension of the machined halves and can effect the crank centering and bearing fit. If done right the anaerobic will be much less than 0.0005″ ( 1/2 part in 10,000). In fact when cases are separated for service I hardly see any sealant but cases surfaces must be true.

    I always check the flatness of the 2 mating surfaces with a machinists steel rule in all directions using a back light on the rule to see highs and lows (they happen especially at bolt and locator pin areas) and lightly dress if needed. If not perfectly flat and parallel there will be seal problems. Clean the surfaces with alcohol before applying sealer, then apply a ‘very small amount of the sealer as a bunch of small dots on both surfaces and spread around with clean finger so you get a uniform very slightly red coating so when bolted there is no squeeze out. All you are doing is filling the factory rotary surfacing machine marks, small scratches and other small imperfections on the surfaces. I have never had a leak at the case joint on the Mercury race engines. I torque in 3 stages in proper sequence from center out.

    Add – I keep the cranks case halves slightly apart while inserting the bolts and nuts in the case to prevent the
    anaerobic sealer from starting to set too quick and it will, prevents extra thickness of sealer from forming.

    I have never tried the Permatex Motoseal, the anaerobic does the job so well I see no reason to change.


    labrador-guy

    Replies: 138
    Topics: 21
    #159605

    My two cents on this question. I come from motorcycle and snowmobile experience and I have found that “yamaha bond” is incredible sealer for any kind of machine surfaces that need to be sealed WITHOUT a gasket. It is thin and after it cures the two halfs stick together well. It is what I use.

    dale

    outboardnut
    outboardnut
    US Member - 1 Year
    Replies: 331
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    #159609

    To Phil 1955 RDE-17S 25 hp Johnson

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