CONTINUOUSWAVE

Q1: what miniature electric light bulb is used in the combined sidelight lamp of a 2004 170 MONTAUK?

ASIDE: the Boston Whaler part number for the lamp assembly is thought to be 1035203. My kids report [the combined sidelights lamp is not illuminating on our 2004 170 MONTAUK. ] I won't be able to access the boat to service the lightbulb prior to our trip.

There could be many reasons that the combined sidelights lamp on you 2004 170 MONTAUK is not illuminating, other than a incandescent miniature lightbulb filament has burned out. Other causes could be a poor connection:

• in the lightbulb holder socket;
• in the electrical wiring
• in a connector that carries the power to the lamps, or
• due to a blown fuse in the circuit that powers the lamp.

Replacement Lightbulb Source

There is a good chance the lightbulb is a Festoon style 12-Volt incandescent type. Festoon-style miniature lightbulbs are often used in boat navigation lamps. The Festoon light bulb in the OEM lamp MIGHT be similar to one available from WEST Marine:

https://www.westmarine.com/ancor-festoon-base-12.0v-15w-0.97a-12cp-297335.html

Poor Contact in Lamp

In an archived discussion, there is a report that failure of the lamp to illuminated was due to a mechanical problem with the lamp fixture. See

2014 170 Montauk Navigation Lamp
https://continuouswave.com/forum/viewtopic.php?t=7153

for more details.

Another archived discussion with useful information on this topic is located at

Replacement Lens for Combined Sidelight Bi-color Lamp
https://continuouswave.com/forum/viewto ... =9&t=10158

This second reference shows nice details of the interior of the lamp assembly.

Electrical Circuit Problem or Fuse
If the cause of the problem of no illumination of the lamp is something related to the electrical circuit, there is a detailed explanation of the circuitry used to control the lamp and the fuse that protects the circuit in a prior discussion at

Navigation Lamp Circuits Used on Newer Boston Whaler Boats
https://continuouswave.com/forum/viewto ... f=9&t=4136