So I have a trailer light connector like this (4-flat)
http://www.etrailer.com/Merchant2/graphics/00000001/dt/t1/18002.jpg

and I want to tow a boat that uses a connector like this (5-flat)
http://www.etrailer.com/Merchant2/graphics/00000001/dt/t1/20016.jpg

I've looked for an adapter to convert between the two online but haven't been able to find one. Anyone have any experience with this particular type of conversion, or better yet a link to the right kind of converter to buy?

Years ago I converted that type of plug. I got the kit from a UHAUL dealer. Give them a call.

If one is male and the other is female just plug them in with the extra hole unplugged, it will work. That's all I know.

Matt

Rob , The color code goes like this.......

White = ground
brown = tail lites/marker lites
green = right hand turn signal
yellow= left turn signal

The fifth wire (blue) is typically tied to your back up lights circuit and its purpose is to disable the boat trailer's "surge brakes" when backing up. If its a big boat with electric brakes requiring a "Brake controller" then the blue wire could be used for the output from the controller . You need to first determine if the blue wire is used for trailer braking .

Hope this helps......... Ken

Thanks Ken,

Your info is totally right on. I thought I had it figured out but I still don't... I gotta take a picture of what I have and post it so you guys can see it. I think what I need is block that attaches to the main truck wires and then has a 4-flat and a 5-flat connector coming off of it. I saw this at uhaul last night but it was a round piece designed to plug into an existing 7 wire plug on the truck.

The other option Lake and I were just discussing is that apparently you can release some hydraulic valve on the trailer just to back it up, then hook it back up when you need the brakes again. Annoying, but it would work. I just need this adapter for a few trips this year.

Rob , If you install a 5-flat on your truck (with the blue wire tied to the B.U. lites) you would be set to tow your buddy's boat .
You could either put a matching 5-flat male on your boat trailer using just the four wires you need or it would be simple to make up (or purchase)a 5-flat to 4-flat adapter for your boat (just omitt the blue wire)
for towing your rig . I guess it comes down to which ever is simplest/cheapest?

Ken

Have you checked with etrailer.com to see if they have what you need?

http://www.etrailer.com/Merchant2/merchant.mv?Screen=CTGY&Store_Code=E&Category_Code=VWH

Ken,
Thx for the link. The first time I looked I didn't see it but I just looked again and they have exactly the right thing. Check it out, this will let me do exactly what I need to do - thankyou!
http://www.etrailer.com/Merchant2/merchant.mv?Screen=PROD&Store_Code=E&Product_Code=37515&Category_Code=A

http://www.etrailer.com/Merchant2/graphics/00000001/hmc/47515.jpg