Re: Sealing crankcase halves, which sealant? 1972 Johnson 6 HP
If one half of the crankcase has slots that a spaghetti type seal would rest in, then use the 3M#847 adhesive. If the crankcase halves are simply a machined fit with each other and do not have the sealing slots, use the Gel Seal.
The confusion is due to the fact that before "Gel Seal" existed in the marine world, the larger horsepower engines incorporated slots in on one half of the crankcase halves (on both sides of the crankshaft). A black spaghetti type seal was laid in the slots, then the 3M sealant was spread on top and around the spaghetti seal material. This resulted in a sufficent seal with no leakage. This same 3M#847 (OMC Adhesive) sufficently sealed the smaller horsepower crankcase halves "without" the slots or spaghetti seal.
With the coming of "Gel Seal", the spaghetti seal slots were no longer needed and "Gel Seal" became the new sealant for all of the horsepower models. Gel Seal does the sealing in the absence of air........ when the two crankcase halves are torqued together.
However, the older still existing engine models that "do have" the spaghetti seal slots will still require the 3M#847 sealant.
