Attwood Turbo 4000 Series II 1749-4 wiring diagram

1749-4 is the retail 12 V water-resistant Turbo 4000 Series II blower for 4-inch ventilation hose. Its role is to move air from the engine/bilge space to an exterior vent. Water resistance does not authorize submersion or mounting where bilge water is drawn through it.

The manufacturer gives 230 CFM open flow and 125 CFM in a specified test system with duct, a bend, collector and vent. Use the installed ventilation path when assessing airflow; the free-air number alone does not establish adequate ventilation for an engine compartment.

Connect yellow positive through the helm on/off switch and specified 5 A fuse, with black negative return. The reviewed instruction table gives 2.9 A at 13.6 V. The catalog uses that operating point; it does not borrow the 24 V blower's current or treat the fuse as consumption. No measured starting surge was recovered.

Size extensions for the actual circuit length, ampacity and voltage drop, and keep connections protected from moisture. The older instruction sheet shows a maximum source-to-fuse distance; use the protection placement required for the actual installation rather than assuming that old drawing makes every long unprotected battery lead acceptable. The catalog terminal limit is a protection-based planning bound.

Mount high above the bilge on a suitable surface, clear of spray and deck wash, with the flow arrow pointing toward the exhaust vent. Follow the recommended angled orientation so moisture does not collect in the housing. Secure the hose over the retention features without crushing the plastic.

Route the intake pickup toward the low part of the space being ventilated while keeping it above possible bilge-water submersion. Run the discharge to the exterior vent with few bends and no collapsed hose. An apparently healthy spinning fan can move very little useful air through a blocked or badly routed duct.

Attwood directs operation for at least four minutes before engine start, followed by checking the compartment for fuel-vapor odor, and operation below cruising speed. The sheet also says not to operate while refueling or above its 71 °C ambient limit. Keep the blower reminder label at the helm.

Commission by checking the direction and useful flow at the exterior discharge, not only the sound of the motor. If flow is poor, inspect duct restrictions, pickup obstruction and rotation/airflow orientation. If it is silent, check voltage at the blower, switch and fuse. Isolate power before servicing; if fuel vapor remains, resolve its source before engine starting.

Attwood installation instructions, manufacturer PDF hosted by distributor, p. 1, establishes wiring, current, fuse, ducting and operating checks. Current Attwood catalog confirms the 1749-4 retail identity; pp. 36–38 distinguish voltage variants and performance. The original instructions and hash are retained locally.