79 Evinrude Piston Skirt Clearance

I have some difficulties accep

I have some difficulties accepting this talk of bearing clearance. It would take more pressure/gap than what is here to compress the outer bearing races in a way that clearance will be changed! This is not a 4-stroke with loose bearing shells and dependable of oil-film pressure. The only question is which sealant will seal off in a proper way!

"I can share your confusion as

"I can share your confusion as those caged rollers and fractured races are really loose and a good coat of oil keeps them going. If the bearings were the only thing to worry about, you would not have a problem with even .010 clearance in the bores.

However- excess clearance equals egg shaped bores. This then exercises the top and bottom seal at idle speeds and is detrimental to the way the internal crank seals are performing. A round laverenth seal, or even slip ring seals would not hold much fuel load in their chamber if they had .010 seepage to the a joining cylinders.

The outer races (held together for assembly by a blind snap ring) will also start to dance around.

So I feel that getting rid of as much sealant in a crankcase parting line is a real good idea."

William - Just finished readin

William - Just finished reading the data sheet on Grey Seal and I have a couple of concerns. It's been drilled into me that I should not use an RTV for the crankcase flange assy. And the data sheet specifically says not to use this product with anything that comes in contact with gasoline. You previously said you've been using this on outboard rebuilds...specifically at the crankcase assy? I like the performance info on this product right up to the point it says no contact with gasoline. There's a lot of gasoline flying around in the lower crank...you've not had any issues on your 2-stroke rebuilds in this area using Grey Seal? This product sounds like an excellent choice for all other areas...I'm just curious. Please let me hear about your specific experience with 2-stroke rebuilds using this product on the crankcase assy. The high-temp performance is outstanding!!

"The races are held in place b

"The races are held in place by pins and will not start 'dancing around'. What further more keeps them in place is the torque of the center bolts, and I suspect that the 'problem' on this case might be the clearance on the outer flange. It is all designed for using Gel Seal and provided it is applied according to specs there will be no build up of clearance. The only question might be if the Gel Seal might hold on the outer flange."

"Morten - You bring up an inte

"Morten - You bring up an interesting point. The gap I have been referencing is definitely on the outside flange. Tomorrow I will take a closer look towards the inside where the heavier bolts clamp down.

I've been studying the Loctite 515 and 518 gel seal. In an aircraft engine forum they said that 515 is NOT to be used on aluminum and only 518 of the 2 should be used. I'm scratching my head on that one...went back to the data sheet and nowhere (that I can see) does it say not to use with aluminum. However, when you look at the strength graphs showing the products on alum vs steel, the 515 shows a shear strength that's 50% on alum. to steel probably due to the increased flexibility built into the product, and 518 is about 75% on alum compared to steel. NOWHERE does it say on either product that you can't use on aluminum. I've submitted a question to Loctite's tech support. I'll let you know what they have to say."

The answer will probably be: I

The answer will probably be: If used on aluminum You are recommended to use a primer.(Loc Tite Primer).

"Here's the response from

"Here's the response from Henkel regarding Loctite 515 & 518 for aluminum crankcase assy applications.

David,
These products are very similar in chemistry with only minor physical differences. 518 is thicker in viscosity which can be considered easier to apply but it also takes longer to cure than 515. You might find that Loctite 515 is more readily available and easier to find locally but either product should work for your appplication.
Best regards

It sounds to me as though either can be used. The 515 has less strength but is more elastic, along with being a bit thinner which could also be a good thing."