Boat Maintenance & Repair Forum

Underwater lights

by mlines » 06 Mar 2016, 21:26

Christmas is a time for treats, things you would not normally buy. This year James wanted underwater lighting. We have seen various impressive displays and thought we had to join in, especially for Henley Regatta, Henley Festival and Henley Rewind.

There are a number of brands on the market, varying from the expensive to the more modest priced. We opted for Bluefin LEDs as they are more within our price range, particularly for colour changing versions.

These are simple devices, only requiring small mounting holes and two wires. The colour sequencing is automatic and controlled by a simple on-off switch. When switched on they start a slow sequence that can be stopped at the colour of your choice by pulsing the on/off switch. A further pulse puts them in strobe mode........

We bought a twin pack as you need two and its cheaper to buy them combined.
Bluefin P6 CC (with protective film on lens)

​When we came to fit them we bumped straight into a major issue. I had only made a cursory check inside the boat and thought I could see the transom. I thought they would be straight forward to fit. However a closer look showed that I could not see the transom at all. There was a blind compartment between the access point and the actual transom :(

I had two concerns:

​The compartment may still not lead to the transom
The compartment may be foam filled

I spoke to Regal Boats in the USA who responded with some helpful pictures of the area, but they suggested it would be near impossible to access. I also spoke to Gibbs in the UK. Between Gibbs and Regal I at least determined that there was no foam filler in the compartment and that it would lead to the transom, but would be very difficult to do.

​The boat has a raised floor which is what is visible in the engine compartment. This floor has a gap between it and the hull and it is this gap that has access to the bulk of the transom.

Therefore I decide to use a circular hole cutter through the internal floor and take a look. This involved laying on the engine and reaching into the back and drilling down, it was not fun!

Here is the Starboard side. I have had to work the drill into position and then drill by reaching in and pressing the switch on the drill. Its approximately a 85mm hole cutter. Take it very gently as the cutter grabs the GRP.

Here you can see the hole that has been cut. I really needed to cut a bit more to the starboard side as you can see there is a rib running for to aft under the hole. However, poking a stiff coat hanger wire in the hole seemed to confirm I could touch the transom.

​Whilst the compartment is not foam filled I am still a bit concerned that it does assist floatation. USA built boats have a mandatory requirement that they have positive buoyancy, they must float even if fully swamped. By using a hole cutter I am left with a nice GRP disk that I can seal back into the hole when I have finished!
For completeness, here is the other side. This was even harder to reach as it was further back. However there was no rib under the hole so its a cleaner access. As you can see there are various bits of plumbing and electricity in the way but the drill fitted behind these ok.

So now the moment of truth, the drilling of the transom. Because of the false floor and various ribs, the actual location that can be used to place the LEDs is limited. The Bluefin instructions give the optimal placing information, including separate of the lights and depth of water. On the Regal it was clear to us that there was only a small section of transom available. I therefore measured up the positioning and marked with a chinagraph pencil.

As part of the measuring I "tapped" the hull with the handle of a screwdriver whilst pressing my ear to the hull. I could hear the hollow sound when I was tapping clear transom and a dull thud when there was a rib/floor seam behind the transom. This meant I found the only real spot it could be fitted.
Marked up for drilling. Note the measurements for your boat MAY BE DIFFERENT!!
The light requires a 13mm hole, a simple drill will do this. I drilled the hole and with some trepidation placed a torch in the hole I had cut in the inside floor. Thankfully, peering in the hole in the transom I could see the light, hallelujah! With the main hole drilled I then could mark up and drill the mounting holes for the screws.
​For the next bit I needed an assistant. Bluefin recommend that the lights are tested before being sealed into location. I therefore had to get the wire through the transom hole and up through the floor. To do this I made a "wire puller" using an old wire coat hanger straightened out. I got my assistant to poke the wire through the transom and "aim" towards the hole in the floor. I then could see the end of the coat hanger through the hole and could pull it (and the LED cable taped to it) through the floor and into the engine bay. This is easier to write than to to, be assured it took a number of attempts!

With both LEDs in place and the wires through into the engine bay I could power up the LEDs for a test!

Having entertained the passers-by in the marina, I could then fix the LEDS in place. In order for the sealant to adhere it is recommended that the surface is roughed up, therefore I rubbed a sanding block on the transom

​ The recommended sealant is 3M 4200. The LEDS themselves have a channel around the edge into which the sealant is applied, it is also recommended that sealant is put around the central cable gland in order to assist with sealing the hole. The picture below shows everything sealed and ready to fit.
Finally the LEDs are screwed into position. Bluefin recommend that they are not too tightly screwed down so that a proper bead of sealant can form. If you look at this picture closely you can see the bead around the edge.

So with the physical fitting done, it is now onto the electrical which is a separate article
Regal 2250 - "Witch Way" - MMSI:235073628
My Regal 2250
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