Adding Electronics to 150 MONTAUK

Electrical and electronic topics for small boats
Saint
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Adding Electronics to 150 MONTAUK

Postby Saint » Mon Mar 09, 2026 11:03 pm

Currently on my 2023 150 MONTAUK there is a Garmin 9-inch chart plotter/SONAR installed. The boat is wired for a trolling motor and has an extra battery box--but no second battery. The only battery is an Interstate 24-M-XHD model.

I plan to install a GARMIN model 115 flush-mounted VHF Marine Band radio--the only size that fits the space at the helm dashboard. I chose the GARMIN radio to keep the electronics all GARMIN, and thus to be more aesthetically pleasing.

I might also install a stereophonic entertainment system with multiple loudspeakers. I would use a FUSION amplifier and JL loudspeakers, installing the head unit and the tweeters also at the helm.

I would contract the work to be done by a marine electronics specialist.

Q1: should a second battery be installed as a House battery?

Q2: should the second battery be the same as the starting battery?

Q3: will flush mounting of the VHF Marine Band radio and the FUSION head unit be practical?

Q4: what will be the impact on the re-sale value of the 2023 150 MONTAUK having the new electronics flush-mounted on the dashboard?

BACKSTORY
I’ve recently relocated my 2023 Montauk 150 to the [Atlantic Intracoastal Water Way or AIWW because ] want better fishing locations and options for near shore fishing if the weather permits.


--Saint

[Moderator's note: thread has moved to SMALL BOAT ELECTRICAL for discussion.]

jimh
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Re: Adding Electronics to 150 MONTAUK

Postby jimh » Tue Mar 10, 2026 9:25 am

Saint wrote:Q1: should a second battery be installed as a House battery?
Having a second battery is always a good idea if the main propulsion engine cannot be rope-started.

As for isolating the House loads from the starting battery, that is always a good plan. However, in the case of a VHF Marine Band radio, the electrical load on the battery will be minimal. The radio will spend 99-percent of the time in receive mode with its audio output squelched. In that condition the current drawn by the radio will be very modest. The radio could easily be connected to the starting battery and would not cause any problem.

A stereophonic entertainment system with multiple loudspeakers will require much more power to operate, particularly if the volume level is set rather loud. Anytime the entertainment system is in use and the propulsion engine is not running and charging the battery, there is a risk of discharging the battery powering the entertainment system. For this reason having the entertainment system operating from a second or House battery is a good plan.

Saint wrote:Q2: should the second battery be the same as the starting battery?
A second battery will be more useful if it has the capacity to also start the engine. The battery should be of the same chemistry as the main battery.

When a second battery is added, you will likely need to change the main battery ON-OFF switch to a different type.

You will also need to consider how you will keep the second battery charged. On some modern outboard engines there will be two charging output circuits, allowing two batteries to be charged indepently. However, on smaller horsepower engines, more likely there will only be one charging output circuit. You will need to decide on a method for keeping the second battery charged.

Typically in the situation of two batteries and only one engine charging output, the second battery is provided with charging current only when the primary battery has been fully re-charged by the engine. This is implemented with an automatic combiner circuit or relay or ACR. You should research the battery switches and automatic devices that can implement automatic charging of the second battery. There are many options. This topic would be best treated as a separate subject.

jimh
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Re: Adding Electronics to 150 MONTAUK

Postby jimh » Tue Mar 10, 2026 9:32 am

Saint wrote:Q3: will flush mounting of the VHF Marine Band radio and the FUSION head unit be practical?
I cannot offer any advice, as I am not familiar with the space available on the dashboard panel and the depth available behind the panel, or with the exact dimensions off all the devices and their mounting hardware.

Saint wrote:Q4: what will be the impact on the re-sale value of the 2023 150 MONTAUK having the new electronics flush-mounted on the dashboard?
Generally adding a VHF Marine Band radio is a very good addition and will add value to the boat.

There is much more to consider when adding a VHF Marine Band radio than just how it will be mounted. For advice about installation of a VHF Marine Band radio on a small boat, see my article on that topic at

VHF Marine Band Radio Installation on a Small Boat
https://continuouswave.com/whaler/refer ... ation.html

As for installing loudspeakers at the helm area, you need to consider the effect of the strong permanent magnets in the loudspeakers on the boat's magnetic compass--if you indeed have a magnetic compass mounted at the helm.

As for effect on re-sale value, the entertainment system may appeal to some buyers but not all.

A much simpler way to provide audio entertainment on a small boat is to use earphones and play music on a smartphone. Many boaters will be annoyed if a nearby boat is blasting out loud music.

As a general rule, any visible alteration of a Boston Whaler boat must be done in a manner that is compatible with the general aesthetics of the Boston Whaler.

jimh
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Re: Adding Electronics to 150 MONTAUK

Postby jimh » Tue Mar 10, 2026 9:42 am

Regarding integration of a VHF Marine Band radio and a chart plotter, there might some advantage to using the same brand for both, but it is not necessary.

In the modern era, a VHF Marine Band fixed-mount radio will be a Digital Selective Calling CLASS-D radio. The typical installation will include some method of providing continual automatic vessel position updates to the radio, in order to allow it to be able to transmit the vessel position automatically when a Distress Alert broadcast is initiated from the radio. Typically the position data comes from the GNSS receiver in a chart plotter, but you can also get modern DSC radios that have their own GNSS receiver built in and do not need to be connected to an external source of position data.

In addition to providing the radio with automatic position updates, the radio should be connected to the chart plotter so that the radio can send position data of other vessels that it receives when those vessels transmit their position, either in a broadcast of a Distress Alert or in reply to a request from your radio to that vessel to provide its position (known as position polling).

jimh
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Re: Adding Electronics to 150 MONTAUK

Postby jimh » Tue Mar 10, 2026 9:45 am

Finally, for a 15-foot boat, you might consider just having a modern handheld radio aboard the boat as your VHF Marine Band radio. As long as you can provide operating power to a handheld radio from the boat battery, this is a very good solution on a smaller boat.

The same approach goes for the entertainment system. If you really need loudspeaker musical stereophonic reproduction, perhaps a quality portable system would be more practical.

Saint
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Re: Adding Electronics to 150 MONTAUK

Postby Saint » Tue Mar 10, 2026 11:15 am

Wow - thank you for the wealth of knowledge and detailed response JIMH.

At this point - I think it makes most sense to add an additional battery as a redundancy. Will need to confirm how it will recharge - electronics and batteries were pre-installed by Boston Whaler. Additionally, 60 hp engine does have a pull start function.

Regarding VHF, to purchase a high-end handheld and recharge via 12v outlet at helm probably makes the most sense.

I will skip the stereo as I agree: a portable speaker is sufficient and nothing is more annoying than the boat next to you blasting music.

NorthShoreWhaler
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Re: Adding Electronics to 150 MONTAUK

Postby NorthShoreWhaler » Tue Mar 10, 2026 3:48 pm

Another option instead of a second battery is to carry a small lithium jump pack. That would provide power if your single battery were to become discharged. The 150 is fairly weight sensitive so consider the impact of adding another battery unless you really need it for your use case.

I put a small rechargeable bluetooth enabled waterproof speaker on my 150 Super Sport. it attaches with a suction cup and provides adequate volume while cruising. These are marketed as shower speakers and relatively cheap.

I agree with the handheld VHF decision. Modern units are quite advanced and can be had with built in GPS and DSC.

Saint
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Re: Adding Electronics to 150 MONTAUK

Postby Saint » Tue Mar 10, 2026 4:14 pm

Interesting point. Could you expand more on the jump pack?

Would it “recharge” your battery through a terminal (male/female adapter) directly the battery?

NorthShoreWhaler
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Re: Adding Electronics to 150 MONTAUK

Postby NorthShoreWhaler » Wed Mar 11, 2026 7:55 pm

A jump pack is a lithium-chemistry battery used for starting a depleted 12-Volt battery. They are small enough to be easily stowed and intended for emergency use. They connect just like car jumper cables.

IMG_0008.jpeg
Fig. 1. A "jump pack" or small battery used to assist engine starting in situations of low battery energy for the primary battery.
IMG_0008.jpeg (18.28 KiB) Viewed 44068 times

jimh
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Re: Adding Electronics to 150 MONTAUK

Postby jimh » Fri Mar 13, 2026 9:38 am

Saint wrote:Would [a jump back battery] “recharge” [the boat battery]?
The “jump pack” (as in a “jump” start which is a derivative from the term “jumper” cables which are heavy conductors that are used to make a connection between or to jumper the terminals of two batteries) is only connected to the engine cranking battery momentarily, just long enough to allow the propulsion engine to be started. Once the propulsion engine is running, the jump pack battery is disconnected. The battery charging output from the propulsion engine then begins to recharge the engine cranking battery.

The jump back battery will have been somewhat discharged from the drain of starting the engine, but the jump pack can be recharged later using its own charging unit that operates from regular 120-VAC power.

The general situation on a boat when the propulsion engine cannot be started from its normal cranking battery occurs because the cranking battery no longer has a sufficiently large stored electrical charge to operate the very large load created by the engine starter motor. Even with a significant charging current being provided by the now-running propulsion engine, to restore the state-of-charge of a deeply discharge cranking battery may take more than an hour or two of running the propulsion engine to get the cranking battery back to a full-charge state.

From Merriam-Webster definition of the noun jumper
—4c: a connection used to close a break or cut out part of a circuit

msteinkampf
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Re: Adding Electronics to 150 MONTAUK

Postby msteinkampf » Fri Mar 13, 2026 9:53 am

My 1990 Montauk 17 came with only one battery. When I installed a trolling motor, I added a second battery identical to the first one, using a combination starting anddeep cycle AGM battery.

https://www.samsclub.com/ip/duracell-agm-deep-cycle-marine-and-rv-battery-group-size-sl34magm/8399630002

Now I have a backup for the starter battery if needed. I contemplated setting up a system to charge the trolling motor battery via the outboard motor, but I found it simpler to just hook up the trolling motor battery to an inexpensive portable charger at the end of each day of use. This setup will work well as long as you don't completely discharge the [trolling motor] battery, which would shorten its lifespan considerably.

I agree with others that a portable stereo would be a good choice.

I have a fixed-mount VHF radio installed in my console, but a handheld model should also be satisfactory.

My personal philosophy about small-boat electronics is to avoid flush-mounted installations when feasible. Although they initially look nice, you will ultimately be left with gaping holes in your console when replacements are required, and finding items with identical dimensions may be challenging.

M
1990 Montauk 17’ w 2024 Yamaha F70LA outboard
1995 Aquasport Explorer 245 w twin 1995 Yamaha 150 HP outboards

jimh
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Re: Adding Electronics to 150 MONTAUK

Postby jimh » Fri Mar 13, 2026 12:14 pm

For my recommendation for a propulsion engine starting battery, see:

Battery Recommendation
https://continuouswave.com/forum/viewto ... f=9&t=4648

msteinkampf
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Re: Adding Electronics to 150 MONTAUK

Postby msteinkampf » Wed Mar 18, 2026 10:42 pm

The X2Power looks like a very nice battery, but at about $400 is kind of pricey. That 48 month "free replacement warranty" looks attractive, though. However, the fine print on the X2Power battery includes the following:

If you store or do not use your vehicle or battery for a period in excess of one (1) month, the
warranty is void unless you fully charge your battery at least once a month with an appropriate
charger or maintainer.


So storing the battery over the winter in a remote location voids the warranty. In addition:

A battery with an open circuit voltage (OCV) of equal to or less than 10.0V for 12.0V rated
batteries, equal to or less than 6.8V for 8.0V rated batteries, and equal to or less than 5.0V
for 6.0V rated batteries will be deemed as over discharged and void warranty due to improper
maintenance of the battery.


So if your battery craps out and has a voltage less than 10 volts, the warranty is void. (You can review the entire warranty here: https://docmgmtprodcdne.azureedge.net/d ... Policy.pdf).

My Duracell cost me $135 last September, but the warranty is only 18 months. My oldest one was manufactured six years ago, but I pull the batteries at the end of the season and keep them on a charger that has a float setting.

M
1990 Montauk 17’ w 2024 Yamaha F70LA outboard
1995 Aquasport Explorer 245 w twin 1995 Yamaha 150 HP outboards

bjohn
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Re: Adding Electronics to 150 MONTAUK

Postby bjohn » Thu Mar 19, 2026 12:08 am

Q3: will flush mounting of the VHF Marine Band radio and the FUSION head unit be practical?


I would not recommend flush mounting a VHF radio or stereo head unit. My Montauk 17 has a flush mounted VHF radio installed by a previous owner. While the flush mounting has worked well, if I was starting from scratch, I would use a "black-box style" remote mount VHF. The Garmin VHF 315 is one example. Using a black-box style VHF radio eliminates the needs to cut a large hole in the console. The radio unit can be mounted inside the console and controlled using the remote handset/mic.

If your GPS unit has the capability of being connected to a NMEA 2000 network, you an also use a black-box style stereo unit and control it using your GPS. A number of manufactures make black-box style stereo units, including Fusion. Some models can also be controlled using phone apps or wired remotes.

In my view, on a small open boat, any convenience gained by flush mounting a VHF radio, or stereo head unit, is outweighed by the disadvantages. The radio will be exposed to the elements, unless you carefully seal the mounting, rainwater will leak into the console, and, in the event the radio is changed, the dimensions of the existing mounting hole will be a factor.

Q4: what will be the impact on the re-sale value of the 2023 150 MONTAUK having the new electronics flush-mounted on the dashboard?


I doubt there would be any measurable impact. Potential buyers are more likely to influenced by the overall condition of the boat, and the age and condition of the outboard motor. However, all things being equal, not having a large hole in the console may be desirable.

You mention wanting to stick with Garmin Electronics. There's certainly nothing wrong with this approach. Garmin makes excellent products. However, there's unlikely to be any practical benefit to using the same brand radio and GPS. Other manufactures also make excellent radios, and you may find another brand offers a better value.

If you do end up flush mounting a VHF radio or stereo head unit, be sure to carefully check the space on the inside to the console to ensure there are no obstructions that would limit the depth of the VHF radio or stereo head unit being installed.

Brad

Saint
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Re: Adding Electronics to 150 MONTAUK

Postby Saint » Fri Mar 20, 2026 3:06 pm

Thanks all for the invaluable advice. Based on responses I’ve decided to go a different route and purchased a Standard Horizon HX890 handheld. I agree with the overall sentiment… flush mount may be nice but could cause problems later on if/when electronics need to be replaced. Black box would be the route the go if I decided for a full set, but for my daily use and the occasional near shore excursion I think the handheld will fit my uses perfectly.

Re: Noco charger, I’ve purchased as well as that could be invaluable at time when needed.