Overview

The Perko 8503DP is a medium duty battery selector switch with alternator field disconnect for 6 to 32 VDC marine electrical systems. It is rated for 250 amps continuous and 360 amps intermittent, and it uses 1, ALL, 2, and OFF positions to manage two-battery setups where manual battery selection is still the preferred approach.

This model is ignition protected, so it can be installed in engine spaces on gasoline-powered boats where that matters. The housing measures 5-1/4 inches in diameter and 2-5/8 inches deep, with a polycarbonate body, brass terminals, and a no-key-lock layout that keeps the switch easy to reach when you need to isolate power or change battery selection quickly.

Key features

• Selector switch with 1, ALL, 2, and OFF positions for manual control of two battery banks.
• Make-before-break action between 1, ALL, and 2 allows battery selection changes while the engine is running.
• Alternator field disconnect helps reduce the chance of alternator damage if the switch is turned to OFF while running on systems with non-unitized alternators.
• Ignition protected for use in gasoline engine compartments.
• Rated for 6 to 32 VDC systems at 250 amps continuous and 360 amps intermittent.
• Surface-mount body with a 5-1/4 inch diameter and 2-5/8 inch depth.
• Polycarbonate body with brass terminals and no key lock.

Compatibility and fit

This switch suits boats with separate start and house batteries, and it also works in twin-switch layouts on twin-engine installations. It is a selector switch rather than a simple on and off disconnect, so it fits systems where the operator needs to run from battery 1, battery 2, or both together.

For replacement work, it uses the traditional Perko bolt circle found on many existing installations, which can simplify swap-outs on older panels. The alternator field disconnect function applies to non-unitized alternators. On unitized alternators with a built-in regulator, that field disconnect circuit is not used.

Installation and setup

The switch is surface mounted, so rear clearance matters as much as face diameter. In tight battery lockers or behind helm panels, allow room not only for the 2-5/8 inch body depth but also for cable bend radius and access to the rear terminals.

It is best placed where battery cables can stay as short as practical and where the knob can be reached without digging into the compartment. In spaces that stay damp or see salt exposure, terminal connections should be protected against corrosion, and the wiring should be done to marine electrical standards by a qualified installer.

Use on board

This is a good match for owners who want direct control over battery selection on a coastal cruiser, center console, sailboat, or small sportfishing boat without moving to an automatic battery management setup. It also makes sense where quick access matters more than keyed security, such as a dedicated battery switch location inside a console, cabin locker, or machinery space.