15pc Lower Unit Gasket 90430-08003-00 8mm Replacement for Yamaha Outboard | Black fiber seals 8x13x1.5mm for drain and vent screws Replaces 90430-08020-00 90430-08801-00 604-45342-00-00 by AUTOMAJOR

15pc Lower Unit Gasket 90430-08003-00 8mm Replacement for Yamaha Outboard | Black fiber seals 8x13x1.5mm for drain and vent screws Replaces 90430-08020-00 90430-08801-00 604-45342-00-00 by AUTOMAJOR

• Replaces Yamaha 90430-08003-00 along with the earlier numbers it supersedes, 90430-08020-00, 90430-08801-00 and 604-45342-00-00, and crosses to Sierra 18-0826. Fifteen seals to a pack, each measuring 8 mm inner by 13 mm outer by 1.5 mm thick, 0.31 in by 0.51 in. Yamaha switched this gasket from reddish orange to black, so a black seal is the current part rather than an aftermarket swap.
• The same seal goes on two screws, not one. Yamaha uses it on the gearcase drain plug at the bottom of the lower unit and on the vent screw above it, and both screws come out for every gear oil change. Two gaskets per service means a pair of spares in the boat bag runs out fast, which is the reason for a pack this size rather than the two or three that come in a dealer envelope.
• Fiber rather than metal is what Yamaha specifies at this joint. The material takes a set against the aluminum housing under moderate torque, stands up to gear oil and salt water, and releases cleanly when the screw comes back out instead of welding itself to the case. A gasket that has been through one heat cycle sits lower the second time, so a fresh one goes on at each service.
• Fit fresh seals when the old ones come out flattened, cracked or stuck to the housing, when a screw will not seat without extra turning, or when the gear oil draining out looks milky and creamy. Milky oil means water has been getting in, and a tired drain or vent gasket is by far the cheapest of the possible causes to rule out before anyone books the lower unit in for seal work.
• Suits Yamaha two stroke and four stroke outboards across the range, from small portables to the large V6 and V8 units, wherever the gearcase drain and vent screws take the 8 mm seal. Stand the lower unit vertical to drain, fit one gasket to each screw, and tighten with hand tools only — these are fine threads in aluminum and a long wrench strips them without much warning. Keep the spare seals in the boat with the gear oil rather than in the garage.