IMCO GATLIN MUFFLER, SWIM STEP (4" Thru-Bolt, sold in pairs)

Inspect muffler body and outer jacket for corrosion, cracks, or perforation — especially weld seams and end caps on stainless steel units exposed to salt water and exhaust heat.

Check butterfly valve / diverter plate for free movement, seat integrity, and absence of corrosion or carbon build-up (critical on switchable ST-450 and Sound Choice models).

Verify solenoid or pneumatic actuator operation (electrically actuated: test solenoid resistance and wiring connections; pneumatically actuated: check air lines, fittings, and compressor output pressure).

Inspect clamp-on connections and hose clamps for tightness, corrosion, and exhaust-gas leakage — retorque to manufacturer specification after initial heat cycling.

Check slip-in baffle inserts for secure retention (mounting pin/hole) and ensure baffle material has not collapsed, cracked, or migrated inside the tailpipe.

Inspect screen rings (Gatlin-type mufflers) for blockage by carbon deposits, water scale, or debris that could create back-pressure; clean or replace as required.

Verify exhaust back-pressure is within acceptable limits for the engine rated power — excessive restriction reduces performance and can damage engines; re-test after any muffler replacement.

Confirm mounting hardware, thru-transom flanges, and backing plates (swim-step / thru-bolt types) show no fatigue cracks, elongated holes, or loose fasteners; inspect transom sealant for water ingress.