Sealing Lower Unit Screws

[Scott in MN]

I've been trying to seal the lower unit gear case on a '69 Evinrude 9.5. The lube keeps leaking through the screw holes. How do I seal these?

The spaghetti seal is on the outside of the screws so the it does not affect their sealing. Also thread sealant does nothing since the threads are only on the upper half of the case. Lube is free to flow down the shaft of the screws and out at the srew heads. I liberally applied sealing compound on the faces of the gearcase halfs when reassembling but there is not much face around the screw holes to form a seal. How do I seal the screws?

 

[ezeke]

Re: Sealing Lower Unit Screws

When the gearcases were made the two parts had perfectly matched faces and a little gasket sealer around the holes would seal it pretty well. Even then they said to dip the screws in s sealer (Perfect seal # 4). A lot of the skegs have been replaced, so it now is sometimes necessary to put sealer on both faces and also to put extra sealer around the outside face of the screw holes as well.

When I redo my split case lower units, I routinely put gasket sealer on both mating surfaces before reassembly. I use Permatex Form-A-Gasket Sealant 1-B on the flanges, and on the spaghetti seal.​

 

[F_R]

Re: Sealing Lower Unit Screws

Those screws are supposed to be tight, which leaves little room for lube to pass under the heads. Give them a couple of whacks with an impact screwdriver. That plus properly applied sealer should prevent leakage.

 

[Scott in MN]

Re: Sealing Lower Unit Screws

I'll try the 1B sealant. I've also got three non stock screws. Wonder if that makes a difference as the stock ones have a non threaded portion near the head. I would think that would make it a little easier to seal them there.