Bunks for lift 25 PF

[bsh102]

Are newly purchased home on the water came with a 10k lift with standard wooded bunks. They were spaced what looked acceptable for our 25 stepped hull. I was looking at the way the bunks were supporting the hull and I am not really liking were they are located. Does anyone have or know what the spacing should be between bunks. They are 12’ long bunks. Thanks for any help.

[jim33042]

I’m not an expert, but maybe my personal Lift experience can help.  
Many times I have seen where the advise is to have the bunks at the distance to match where your boat stringers are.  Start by looking at the bunks on your trailer or You can look in your rear center hatch and get the measurement for either side..and then set your bunks to be the same width.  Moving the bunks is easy enough to climb out and loosen the bolts (having tethers on each wrench will save you from going back to the store for more), then just move each bunk a couple inches at a time at each end (a rubber mallet or hammer does the trick) till you get the desired width. Your bunks are set so that the last boat was centered as it sat Away from the the guide poles and also from a dock extension between the vertical beams, if you have one.   Measure the distance from center of cradle where the bunks are set and compare front and rear to your boat, you will have to reset that distance to safely keep your boat side off off any dock extension and to not have the boat pushing against the guide poles (But you can move the guide poles separately once you have the side of you boat at the distance you want front the dock extension.
Tricky part, the spacing Width you come up with needs to be safely set so that your drop on the “v” of your boat bottom doesn’t come in contact with the aluminum lift cradles underneath.  I had to add spacers under the wooden bunks to get a safe height.  The wood bunks will eventually sag or even bow outwards over time and Will need to be replaced.  I eventually went with aluminum bunks with decent bumper material.  You can install either yourself if you are comfortable working over water.

the wooden Bunks float, so be careful when dropping the boat down to water level, once you boat is ready to float, some installs will leave you needing extra weight to safely drop the lift below the boat without unraveling the wire rope at the motor.  Also, check your zincs, you should have one on each beam going into the water, I hang large plates off of each.

[jim33042]

Also, consider where boat is evenly centered for weight on the cradles.  A boat lift installer will usually place a sticker on the back of the boat so that you know (‘guide pole here’) where your back guide pole should be in reference to your boat. Consider engines, transform extension, fuel tank placement and front overhang of boat.  If you guess at it and lift boat, strum the wire ropes when the boat is out of the water.  They should sound close to the same, if one is holding more weight you should be able to tell from the sound as to which one is holding the extra tension.

Once you set the boat where you want, you can splice in some ropes off of the guide poles to your cleats to help get the boat lifted out of the water, this can make for easy on/off if you are by yourself, but make sure you have main line to the boat dock for securing boat otherwise.

[SCFD rtrd.]

Put your boat on the lift and pick it up until you can easily see where the hull is sitting on the bunks. This will tell you where you need to add material to accommodate for the step or steps. You will see gaps where the hull is not supported and a lot of weight is sitting on those little fiberglass steps.  I have a 23 HPS with one step. I had to add a 1 1/4 " piece of synthetic decking to the last 8 feet of the bunks (approx. from console to transom). Now every inch of my hull is supported. 

The bunks should be under the stringers, as jim33042 suggested. 

[bsh102]

Thanks guys for the information. I decided to order new aluminum bunks and cross members. The galvanized was an eye sore, structural sound but ugly. The lift guys that are doing the work said they will set it up for my hull. When I talked to them, I explained to them about the steps and they said no issue they have done lots of stepped hulls. So we will see what they do.

[bsh102]

Well the lift guys have been dragging their feet to get the galvanized replaced. I could not deal with it not being right for the time being. I got the measurements of the stringers and went to work. Got the bunks loose and moved them to the proper spacing. I pulled the boat back up to the lift and it’s pretty solid now. However, sitting on the patio and I look out at the dock and see lots of daylight between the bunks. WTH, the bunks may be sitting on the stringers but there is not much hull sitting on the bunks. I think more hull was on the bunks when they were sitting at 24” than they are now at 33” on center. I did see SCFD post on another thread. I do believe that is the only way to fix the issue. Kinda of wondering how the lift guys were going to fix the gaps. The front part of my hull does not touch the bunks at all. It has three contact points, each step and the last 14” of the bunk. Not liking this at all.

[smooth move]

read the post in General Forum above. it deals with this.