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  Extending Battery Cables By Using A Terminal Post At Transom as a Splice Point; Mounting Location for Such a Splice Point

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Author Topic:   Extending Battery Cables By Using A Terminal Post At Transom as a Splice Point; Mounting Location for Such a Splice Point
jharrell posted 01-18-2011 05:27 PM ET (US)   Profile for jharrell  
I am in the process of moving my battery from the stern to console on my Classic Montauk.

Based on the excellent advice here I am going to mount a high amperage battery post in the transom area where the original starter cables from the motor can be tied to the new #2 AWG battery wires coming through the rigging tunnel from the Console.

All the information necessary to complete this project was located in this thread:

Everything except advice on where to mount this new battery post.

The battery post is a Bluesea systems dual battery post as seen here:

I currently see 4 possible locations each with good points and bad points.

1. High on the rear starboard gunwale near where the old battery switch was. where the railing protect it from passengers making contact with it, and very dry. The existing wiring from the old motor is the correct length as the old switch was there.

2. Lower on the starboard side of the splashwell. This make the rigging somewhat neater as cables will not be running up to the gunwhale and is still out of the way for the most part except I have a kicker mounted there I would hate to be bumping into the post with my legs when operating it.

3. On the centerline mounted to the splashwell. This is where many seem to mount fuel-water separators. Even neater rigging closer to the tunnel, although I am concerned with it being out in the center of the boat causing interference issue when moving around.

4. In the tiny bilge area under the wood cover(I did measure it will easily fit). I like this location the best as far as keep it out of the way and having the shortest cable runs( for both expense and efficiency). My greatest concern here is it possibly being submerged for short periods as water drains in there.

Any opinions or experience with the battery post mounting and the over all moving of batteries to the console on a classic Montuak is welcome.

jharrell posted 01-18-2011 05:49 PM ET (US)     Profile for jharrell    
On second review of the thread I referenced I completely missed Jim's advice on mounting the posts high on the bulwarks to avoid water / spray.

That location is not ideal otherwise, but water and electricity are indeed a bad combination.

L H G posted 01-18-2011 06:17 PM ET (US)     Profile for L H G    
I remember seeing a factory rigged white Montauk of the late 90's era at a dealership, and the factory had placed the terminal posts on the starboard, angled outside side of the splashwell (if I remember correctly!). This way everything can be tied to the rigid steering cable which takes an approximately same route. The posts should come with red and black plastic covers over the connections.
jimh posted 01-18-2011 06:20 PM ET (US)     Profile for jimh  Send Email to jimh     
Also consider using liquid electrical tape, a semi-flexible insulating compound that can be painted onto the terminals, to create complete insulation and protection. You can even get the liquid tape in red and black colors: Liquid_Tape_-_Electrical_Insulation

jimh posted 01-18-2011 06:23 PM ET (US)     Profile for jimh  Send Email to jimh     
The StarBrite brand is perhaps more familiar to boaters: ProductCat=Home%20Care& ProductSCat=Liquid%20Electric%20Tape%20%28Home%29&ProductSSCat=

jharrell posted 01-18-2011 07:15 PM ET (US)     Profile for jharrell    

Thanks for the memory of a factory rigging. I had read here that Boston Whaler did move the batteries to the console in later models of the Classic. These references never mentioned how it was done, I actually assumed they did a continuous connnection from console to motor. Its always good to know what Boston Whaler would do themselves.


I intended to use some sort of protectant, either dielectric grease or the liquid tape. The liquid tape is appealing creating hopefully a water tight seal, although more difficult to remove and reapply later if needed.

Any opinion on the liquid tape holding up in the bilge area? I still have the idea this is the perfect location other than the water issue.

L H G posted 01-18-2011 08:48 PM ET (US)     Profile for L H G    
Also, you might be able to get some information and photos from an owner of a later 90's Montauk, or from Chuck Bennett at the factory.
White Bear posted 01-19-2011 02:40 PM ET (US)     Profile for White Bear  Send Email to White Bear     
For what it's worth, when I did it for a '20 Outrage the battery post connector went neatly on the starboard gunwale - a dry location with an easy fit for the cables.
jharrell posted 01-19-2011 09:10 PM ET (US)     Profile for jharrell    
Based on all the advice so far I am probably going to mount it on the starboard gunwale or splash-well, perhaps even right under my kicker.

The bilge area would neatly hide it, but the water intrusion issues seem too risky.

I will post updates when it is complete, I am combining this project with adding Baystar hydraulic steering and a powered jackplate since it works out better redoing the rigging.

an86carrera posted 01-20-2011 06:44 AM ET (US)     Profile for an86carrera  Send Email to an86carrera     
Why wouldn't you get #2 cable long enough for the entire run?
Thus avoiding all of the problems associated with an exposed connection capable of over 100amps of shorting fun?


Chuck Tribolet posted 01-20-2011 08:12 AM ET (US)     Profile for Chuck Tribolet  Send Email to Chuck Tribolet     
My '97ish Montauk has a continuous battery cable from console
to motor, and I'd recommend doing that.


themclos posted 01-20-2011 09:39 AM ET (US)     Profile for themclos  Send Email to themclos     
I would agree with those who suggest a single cable run from engine to battery.


jimh posted 01-20-2011 09:47 AM ET (US)     Profile for jimh  Send Email to jimh     
Avoiding connections in a high-current cable which is exposed to the weather is the best approach. But locating the connections outside the rigging tunnel is much better than making a splice in the rigging tunnel.

Leaving the battery in the stern is also a simple solution.

jharrell posted 01-20-2011 01:13 PM ET (US)     Profile for jharrell    
I intended to do a continuous run but the immediate issue I saw with that is the existing wire is #4, the new wire is #2, the rigging port on the motor is already packed to capacity, I would have a very difficult, if not impossible time running #2 in place of #4 through there.

Then in all the research done here it has been consistently recommended to do a battery post mount, probably because of the wire size issue, and this seems to be what Boston Whaler themselves did and recommend.

The battery post solution is nice because it does give me options for other items being hooked up to power back there such as if I got a charging circuit for my kicker and perhaps my jackplate.

Leaving the batter on the stern is obviously the most simple choice, however I am going with a dual battery setup for redundancy, and the single battery already takes up enough space back there to be annoying. Also since adding my kicker also on that side, it would be nice to redistribute weight more forward to compensate.

I am going to examine doing a continuous run again but it might actually require motor cowling modification to accomplish.

Phil T posted 01-20-2011 06:59 PM ET (US)     Profile for Phil T  Send Email to Phil T     
I strongly recommend a single run to the console. I moved my battery to the console on my Outrage 17 this spring.The existing four-foot pigtail cables were 4-AWG; the new wires were 2-AWG. I removed the wiring grommet and enlarged the dedicated holes for the cables. I also used a different size lug on the engine end for the studs on the motor.

I learned my lesson regarding battery cables on my Montauk. The prior owner buried a splice in the tunnel. Nothing but problems.

contender posted 01-20-2011 07:31 PM ET (US)     Profile for contender  Send Email to contender     
Why do you want to mount a terminal in the rear of the boat? Just have one piece cables that run to the engine to the battery. I have my battery mounted under my console. I use wing nuts on the battery; when not in the water the neg comes off. I ran another 8-AWG wire [from] the battery to a fuse panel that runs my lights, water pumps and other equipment. The more connections you have the more chances of problems you will have, Keep it simple.
jimh posted 01-21-2011 09:08 AM ET (US)     Profile for jimh  Send Email to jimh     
If you replace the original engine battery cables with ones of larger gauge, you should use a cable of similar type, with a very high conductor count and flexible rubber insulation.
Liteamorn posted 01-21-2011 10:10 AM ET (US)     Profile for Liteamorn  Send Email to Liteamorn     
Have you ever tried pull starting your engine? I installed an on off switch instead of a second battery/battery switch after I tried pull starting the engine. These smaller engines turn over quite easy and you could eliminate a lot of weight, rigging and cost.
jharrell posted 01-21-2011 12:47 PM ET (US)     Profile for jharrell    
This is the cable I intend to use:

It is not cheap, but I do not want to skimp here, and I have had good experience with Anchor products.

I am set on the decision to move the battery. It takes up too much space back there, while I have plenty of extra space in the console. A two batteries at about 100lbs will actually be a benefit when placed near the front of the console, vs the 50lbs off center near the stern along with my kicker which is about 60lbs. Getting the battery switch in the console is a plus too (semi hidden behind a lock and out of the way as well).

I can rope start my engine(Merc inline 6 90hp) but I would hope to never have to try with two batteries semi protected up in the console. Also if I upgrade to a newer engine rope starting might not be an option(unless its an Etec which I am sure will be pointed out).

Definitely some conflicting views here on the battery post or continuous run, I the previous post I found about moving the batteries forward seemed to consistently recommend a post.

jimh posted 01-21-2011 01:11 PM ET (US)     Profile for jimh  Send Email to jimh     
The ANCOR linked cable is high quality and very flexible. However, you really do not need extraordinarily flexible cable if you are using the original battery cables to attach to terminal posts. The new battery extension cable running from the cable posts to the battery under the console can be less flexible, which usually means less expensive cable.
contender posted 01-22-2011 11:48 PM ET (US)     Profile for contender  Send Email to contender     
I'm a firm believer in larger wires, They do not load up your starter, electricity flows better, and they have less resistance. I just checked my battery cables and they are 1/0 in size. You may laugh but I have had the same cables since I rigged the boat back in 1975. They are connected to the battery by wing nuts and then to the engine, there are no breaks in the run/line anywhere. I used copper lugs that I solder on each end. I then dipped them in liquid tape and used heat shrink as well. I then ran 2 #10's(off the battery) to a fuse panel for all my other stuff (lights, pumps, radio, etc.) When I place the boat on the trailer I disconnect the battery. I also replace my battery about every two years....Take care
cscott posted 01-29-2011 12:36 PM ET (US)     Profile for cscott  Send Email to cscott     
[I]f you have an oil reservoir, you can put your posts on the outside of that and cover with the rubber booties. That's what I did on my [boat], but I do not know if you have a two-cycle motor. [Using the lid of an oil reservoir for a two-cycle engine as a surface to mount the binding post terminals for making a high current connection in the primary battery distribution cable to the outboard motor] work[s] GREAT.
jimh posted 01-29-2011 08:24 PM ET (US)     Profile for jimh  Send Email to jimh     
I suspect that using the surface of a two-cycle engine's external oil reservoir tank as a mounting surface for high-current binding post connections of the primary power distribution will not be in compliance with American Boat and Yacht Council (ABYC) recommendations for electrical practice. They certainly would not be in compliance with my own notion of how to properly install electrical binding posts for any sort of power distribution, and particularly not for a high-current distribution like the primary battery to engine cables.
jharrell posted 01-29-2011 09:06 PM ET (US)     Profile for jharrell    
I have a two-stroke, but it has no reservoir it is pre-mixed in the gas instead.

Two-stroke oil is nearly as combustible as gasoline. I would think it would nearly as big a safety hazard as mounting the post to my gas tank.

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