Trailer Lights & Towing

My recently upgraded boat uses a 5 pin light connection (see image). I use an older towing vehicle which only has the 4 pin connection.

I live 1.5 miles from the river. Is there any issue with just plugging the 5 pin trailer lights into the 4 pin connector? Again, I’m towing 1.5 miles at 35mph tops. The research I’ve done says that the 5th pin could be for trailer brakes or reverse lights? I have also read something about a reverse braking lockout?? It’s confusing, but I’ve used the boat so far without issue. However, it’d be ideal if I had working lights. Thanks for the help!

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The 5th pin is likely for the brake lock-out. Without it your brakes will engage while backing up. Otherwise you’d need a manual pin installed into the tounge to lock out the brakes.

biggill wrote:

The 5th pin is likely for the brake lock-out. Without it your brakes will engage while backing up. Otherwise you’d need a manual pin installed into the tounge to lock out the brakes.

I’ve used the boat multiple times and haven’t noticed the brakes locking out (which is why I’m confused). I’ve backed it into landings and up an uphill driveway with no issues.

With or without the 5 pin harness plugged in?

If the brakes don’t engage without it plugged in to a proper 5 pin receptacle, it tells me you have an issue with your brakes. Nothing to worry about if you only ever go a couple miles at slow speed. But something to be aware of.

I’ve attempted it with both the lights plugged in (4 to 5 pin) and not at all and have never noticed anything when backing. The boat is a Tuffy 1700 that is only 17′ long and Is a 1200lb hull. Is it possible that there are not any trailer brakes, but it’s wired for them with the 5 pin? I do not have the trailer owners manual. It is a 2007.

Not likely. I’ve never seen one until I bought me current boat. It’s difficult to find a 7 pin to 5 pin adapter. There would be no reason at all to have a 5 pin without brakes.

That’s a pretty light boat but it could have brakes. Take a look behind the rims for drums or disk brakes. Got a pic of the trailer tounge?

The trailer could simplify have reverse lights on it, get a 7 to 5 adapter and plug it in, unless you only have a 4 wire, which I would replace with a 7 wire.

surge brakes lock up backing up, electric will not. I am guessing you do not have surge brakes. the 5th wire would be powered by your reverse lamps, hence bypassing the surge brakes so you can back up. like said, maybe there was back up lamps at one time.

biggill wrote:

Not likely. I’ve never seen one until I bought me current boat. It’s difficult to find a 7 pin to 5 pin adapter. There would be no reason at all to have a 5 pin without brakes.

That’s a pretty light boat but it could have brakes. Take a look behind the rims for drums or disk brakes. Got a pic of the trailer tounge?

To my knowledge, there are not trailer brakes (despite having the 5 pin lights). Here are some pictures…what do you think? Can I just use a common 4 pin connection from the tow vehicle into the 5 pin from the boat trailer?

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biggill wrote:

There would be no reason at all to have a 5 pin without brakes.

Yes there is; This is a 2007 trailer, Somebody replaced the wiring or the plug end of the wiring and the 5 pin was what they bought. Not the right plug end to use, but that may have been the only one available at that time and place.

I am not surprised the trailer does not have brakes. I’d also expect that if you opened up the wiring harness you would find the 5th wire is not connected to anything at all. Using it as you have been is just fine.

buckybadger wrote:

Here are some pictures…what do you think?

You do not have brakes on this trailer.

-J.

I would have to double check, but I’m pretty sure I picked up a 7 pin adapter at Wal-Mart that has adaptor slots for 4 and 5 pins plugs. Didn’t need the 5 pin but it was what they had and I needed a new one.

I picked up the same adapter as well when I bought the vehicle and towed it with the newer pickup. It will go from a 7 pin to either a 4 or 5 pin. Unfortunately, the vehicle I will be towing with is NOT wired for a 7 pin connection. I don’t want to waste time and $ doing so considering it’s an old vehicle that tows a boat less than 2 miles one way to the landing. I was hoping to get by with just the 4 pin connection from the vehicle that’s currently on there. The catch is that the trailer has the 5 pin (for an unknown reason) as it’s been confirmed that there are not brakes.

buckybadger wrote:

I was hoping to get by with just the 4 pin connection from the vehicle that’s currently on there. The catch is that the trailer has the 5 pin (for an unknown reason) as it’s been confirmed that there are not brakes.

You CAN use it just fine. IF the plug on both the trailer and the tow vehicle are wired correctly, plugging the 5 pin from the trailer into the 4 pin from the tow vehicle will work just fine.
I would check the 5th pin just to make sure it is not “hot” for some unknown reason. Don’t need it shorting out as it will be exposed. (if it is “hot” this means something is wired incorrectly and needs to be corrected.)