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Author Topic:   Lightbulb For 1982 Sport 15 Combined Sidelight Lamp
R DAVIS posted 12-06-2013 05:57 PM ET (US)   Profile for R DAVIS   Send Email to R DAVIS  
I have a 1982 Sport 15 with the original chock-type red and green combined sidelight lamp. I need a replacement bulb, but have not been able to match it anywhere. The bulb base is smaller than most bulbs I've found at marine dealers, and there is no number visible on the bulb.

Does anyone know a part number for the bulb,and where it is available? Is there a LED type drop in replacement bulb available? Thanks--Randy

jimh posted 12-06-2013 06:56 PM ET (US)     Profile for jimh  Send Email to jimh     
The first step is to identify the lightbulb base. Next, you know the voltage, so it should not be too hard to identify the possible lightbulb choices with a particular base and a 12-Volt rating. Usually a lamp like a combined sidelight lamp will use lightbulbs of about 15-Watt rating. The lightbulbs are single filament.

Typically the lamp socket will be a bayonet base. There are not an infinite variety of these. Perhaps you can browse a manufacturer's website site like the one I will link below for some typical miniature lightbulbs with bayonet bases:

You can also make contact with Boston Whaler customer service via telephone. I am sure they can tell you the OEM lamp and lightbulb. If your boat's lighting has not been modified, that information may be all you need to find the proper replacement.

jimh posted 12-06-2013 07:06 PM ET (US)     Profile for jimh  Send Email to jimh     
Usually the bayonet base will be the very common BA15s size. In 12.8-Volt lightbulbs with this base there are two common lightbulbs

1003 = 12-Watt, 189 Lumens

1156 = 27 watts, 402 Lumens

R DAVIS posted 12-30-2013 05:39 PM ET (US)     Profile for R DAVIS  Send Email to R DAVIS     

I went to my local O'Reilly Auto Parts store and was able to match the bulb after taking it out of the package. It is a number #57 bulb and they have nice nickel plated base bulbs.

They didn't look like the same base diameter while still in the blister pack. I guess my eyes are getting old.

Thanks to all who replied.

South Texas, where fishing is great year around.

jimh posted 12-31-2013 02:21 AM ET (US)     Profile for jimh  Send Email to jimh     
Thanks for the follow-up. Did it look like this:

R DAVIS posted 12-31-2013 11:00 AM ET (US)     Profile for R DAVIS  Send Email to R DAVIS     

Yes that looks like it except the ones I purchased have a nickel plated base.

jimh posted 01-01-2014 09:07 AM ET (US)     Profile for jimh  Send Email to jimh     
The lightbulb with a nickel-plated base sounds even better for marine use. Thanks for the information.
jimh posted 01-05-2014 01:09 PM ET (US)     Profile for jimh  Send Email to jimh     
I am surprised by the #57 lightbulb electrical power and light output. It is only a 3.4-Watt lightbulb, and it only produces 2 Lumens of light. That does not seem like it would be enough for a navigational lamp. Even on a small boat (less than 12-meters in length) the sidelights are supposed to be visible at a distance of one mile. (Cf.: )

Can a light of 2-Lumens, shining through a color filter, be seen at a distance of one mile?

To get the answer, I visited the federal regulations at sid=a9fda2309970ca6ae93268c1355ebfa0&rgn=div5&view=text&node=33: 39&idno=33%20%20%20#33:

The regulations give a table for the luminous intensity of the light to meet the distance requirements. For a distance of one mile, under the standard conditions used in the regulations, the required luminous intensity of the light is calculated to be 0.9-candelas. The candela is a unit that is equal to one Lumen.

Since the lightbulb produces 2-Lumen, it should be visible at a distance of one mile. However, we do not know the light loss that occurs in the filter of the sidelight that turns the light to red and green.

Using a table of filter loss factors for photographic filters, at , a red filter, Wratten 25, has a filter factor of 8. This means that only 1/8th of the light is allowed through the filter. That would suggest the light output would decrease to 2/8 = 0.25-Lumen. That is too dim to meet the regulations, which require 0.9-Lumen.

If we use a green filter, Wratten 58, the filter factor is 6. That means 1/6th of the light is transmitted through the filter. If we start with 2-Lumen we will end up with 2/6 = 0.33-Lumen, and, again, this is too dim to meet the regulations.

Working this problem in the other direction, to get 0.9-Lumen out of a red filter with a filter factor of 8, we have to start with 7.2-Lumens. We look for a 12-Volt incandescent miniature lightbulb that produces at least 7.2-Lumens of light.

A suitable lightbulb will be the trade number 1895 bulb. It is an inexpensive ($2.45) miniature lightbulb with 4-Watts of electrical power, a BA9 miniature bayonet base, but it produces 25-Lumens. That is plenty of light for the sidelight visibility.

I am just guessing at the filter factor for the red and green filters of the sidelight. I think they are probably higher than 6. If we use a deep red filter, Wratten 29, it has a filter factor of 20. With a 1895 bulb we have 25-Lumens of light, and out of the filter we would have 25/20 = 1.25-Lumens. That is about what we need to meet the visibility requirement of 0.9-Lumen.

I believe that the 1895 bulb is probably a better choice for a replacement bulb for the sidelight fixture than the 57 bulb. The 57 only produces 2-Lumens, which is very likely to be too dim to meed the required visibility.

goldstem posted 01-06-2014 01:26 PM ET (US)     Profile for goldstem  Send Email to goldstem     
Jim, you are probably correct, but that is a rather significant difference in heat output as well, and that would worry me.
jimh posted 01-06-2014 03:14 PM ET (US)     Profile for jimh  Send Email to jimh     
There is very little difference in heat. The 57 bulb consumes 3.4-Watts and the 1895 bulb consumes 4-Watts. The difference in heat generation is very small, only 0.6-Watts.
goldstem posted 01-07-2014 12:40 PM ET (US)     Profile for goldstem  Send Email to goldstem     
Wow--they get a 10-time increase in light with only 1/6th extra wattage. Very nice, and that does seem like a good deal.
jimh posted 01-08-2014 11:33 AM ET (US)     Profile for jimh  Send Email to jimh     
I hope it is not a misprint in the specifications!

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