Wiring a boat lift

I’ll preface this by saying I am NOT an electrician, but I’ve been around home building and repair , I’m not an idiot, but I’m no expert either. I’m installing a boat lift in my back yard, salt water location. I have questions concerning the type of wire to use. The flexible 5 conductor leads to the motor are rated for UV and moisture exposure, obviously due to their location. The near motor can be run directly from the switch to the motor from the enclosure the switches are mounted in. I need to run wire underwater to the far piling and lift motor, and the question arises - can I use 5 indvidual THHN leads in pvc, then through flexible wet rated conduit, or must I make a continuous run from the switches to the motors using the same wet rated wire as on the near lift motor? Why and why not? Do I have options? I have searched and attempted to decipher codes, but I’m not getting a clear understanding. Thanks…

You can cut that cable and put a wet location box at both ends for your THWN conductors that go under the water. That is how they all get wired here. You could also order enough SJOW cable to do it if you don’t mind opening up the drum switch and motor box. It still should be in PVC conduit for protection. Just be sure the underwater part won’t get hit by the boat. I really prefer going overhead if at all possible. The manufacturer might also sell you a factory made cable to do it if you are worried about the listing. Technically changing anything might affect that.

You used the designation of THWN rather than THHN. What’s the difference between the two, technically speaking? Can I use THHN, or must I use TWHN, and why? Thanks.

THHN is not rated for a wet location ( such as in conduit ) add the W and it is fine. Important to know that THHN is usually listed as THHN/THWN in most call cases now.

Also…sad to say this is not a DIY Forum and you will probably be better served visiting www.doityourself.com as some of us will explain electrical issues but not explain to a non-electrician on how to do them.

As for running the PVC underwater…as greg states I would be VERY careful on damage to the conduit and thus the wires inside of it. if this is a loading boat area how about running the conduit around the under decking versus out where it could be damaged.

I will also add that when you are doing these connections you need to ensure your connection points are above the datum plane of the electrical system in case of tidal changes and so on…and remember the connections should be no less than 12" above the decking or pier.

Also ANY wiring in the water will be something you will need to call your local AHJ about…they will have specific guidelines possibly that you will need to follow…

Many thanks to you, Paul and Greg. You gave me exactly what I was looking for. I spent a great deal of time searching the net using a variety of phrases but couldn’t get those answers. Even sites that purport to be for diy’ers were giving out conflicting information, so I searched further. I stumbled on this site, and although it is for professionals, you had the courtesy to answer me politely without preaching. My desire to do this myself comes from several bad experiences with so-called electricians who did more harm than good for me. (can you say GFI hooked up backward?)

Just to clear up a few items, the motor switches are in a gasketed non-metallic enclosure four feet above the deck, and 6 feet above mean high tide. The controlling water depth is only three feet, so I intend to bury the conduit in the muck, at the end where the bow is, to minimize that risk of damage. Unfortunately, one of the piling pairs sit away from the dock, as stand alones, so I have no choice but to run wire under vs overhead.

Again gentlemen, I truly appreciate your kindness and help.

Best regards, David

If the pilings are tall enough you can still put a stringer across them to support a raceway. You can also think about a top once you get going. They make some that just bolt up to the tops of the pilings. Your boat will last longer

I’ve thought about it. But living in hurricane country, I’d rather not have anything exposed that I don’t need to. The boat has a full cover, so sun load isn’t too much of an problem. The other issue is that the boat is a high freeboard center console with an arch, and it is ‘tall.’ Thanks for the thought…

`I am in South Lee County Fla, you don’t get much more “hurricane” country. The tops I am thinking about have a removeable cover so you just have the ribs sticking up in the wind when you take the cover off. I made my own with PVC conduit bows and it survived Charlie up but the silver poly tarp I used for a cover succomed to a coconut strike. I was out $30. The commercially made ones from Punta Gorda use aluminum framework and a custom sewed top, still heavy poly.

As fou your electric, if you don’t “drive through” your lift you could still run a PT stringer across the front pilings to support a raceway and stay out of the water.

I live in Cape Coral… yup, I’ve got the t shirts from Charley and Wilma. We live on the Caloosahatchee, and we are more prone to wind and water damage than those living on canals. I watched my neighbor’s dock get picked apart during Charley, and it became very apparant that less dock, less cover, and less equipment is much better.

I don’t have a drive through lift, but I have set it up so the motors and control box are at the seawall end instead of the exposed end. Even with a shallow controlling depth I will have to work hard to do any damage to a conduit buried in the muck, since only the bow portion of the keel will pass over that area. Unfortunately, due to the piling heights and the freeboard of the boat, an overhead run would probably be more prone to damage than a buried one.

I appreciate your thoughts on a cover - I’d like to have one just the same, the sun load down here is tremendous, as you well know!

Regards, David

I really did see the difference when I put up a cover. It is worth thinking about but you may have “cape” troubles if you do it. I know they were trying to ban boat covers. Ruined people’s view.
One more thing to think about with your underwater raceway. If this is near the seawall you may be burying it in rip rap some day. That is the common way to fix seawall blowouts at the bottom of the wall (where they usually fail).
I am on the Estero River west of 41. Charlie gave us a pretty good blow but not as bad as the people northwest of us. I did have a 50’ mango tree on my screen cage and a big ficus on the shed. We lived through Wilma pretty well unscathed but Charlie had blown down the trees that were coming down and we had the place tied down and shuttered up well.

BTW if this is an Ace lift plate, and most around here are, you have 5 conductors in that SJOW cable. Bear that in mind when you are buying material.
I imagine the Aluma<sumpin> lift plate that is most of the rest also uses the same type motor and will need the same cable or conductor set.

This site has some info on the drum switch and the various motor wiring diagrams. (about page 4 and 5) You may need the “6 lead dual voltage” diagram if you have to replace the motor some day since that is the easiest universal replacement motor to find that will work. The Ace motor is 4 lead, at least on the old ones like I have worked on.

We were shuttered up for Charley, didn’t bother for Wilma. No damage from Charley, just a few lifted roof tiles and some badly molested vegetation. We had a smaller boat at the time, it was in a storage building. Our house is a two story, cbs bottom, stick built top. Man, you could really feel the storm upstairs! We went one full week without power, the day after the storm we put the moho in the drive way and fired up the generator to power the fridges and freezers. Good thing it was a 12.5 kw dweezel…never missed a beat.

I’ve got a Quality Boat Lift, mostly ‘aluminum’ with stainless parts on the motors. Yup, it’s 4 conductor w/ ground. Thanks for the link, it may come in handy some day.