Presto XL500 Davit Lift Installation

[ttmott]

I thought I would provide some details on the installation of a Presto marine XL500 Davit on my 2006 52 Sedan Bridge.
Difficulty (1 to 10 with 10 being the most difficult):

• From a technical difficulty aspect, it is about an 8.
• From an installation difficulty aspect, an 8.
• From a tool aspect (do I need speciality tools), an 8.

A couple of things regarding the boat:

• The swim platform on the 52DB is big and well reinforced underneath. Plenty deep for the installation of Presto's 42-inch rolling lift. This allows the dinghy to set aft of the platform or tucked tight into transom or in-between.
• Unique to the 52DB is the hull extends to the back of the swim platform and access under the platform is from the lazerette. So, all of the bolting and hydraulics are in dry areas.
• My boat has a large watermaker in the lazerette so there is little room for the hydraulic power pack. I had to get inventive for its installation.

Here is a picture of the lift -

 

[ttmott]

Making Room for the Hydraulic Power Unit -
In my case the power pack needed to be mounted vertically. Not in Presto's literature the HPU needs to be mounted laying down. Unfortuniately, this simply wouldn't work in my limited space which is in front of the generator.
First, I built a mount for the pump unit then had to change the side oil pickup to a bottom pickup. This was simply removing the plastic 90-degree fitting in the oil reservoir and install in its place a 3/8-inch by 6-inch BSPT bronze nipple.

Then there is a deck support post which holds the generator's racor filter that I moved aft about six inches and rotated slightly so the Racor hoses would clear the HPU brackets.

Then install the HPU so it won't interfere with access and maintenance of the generator -

 

[ttmott]

Electrical Installation -
The Presto HPU demands a lot of current at 12 Volts DC. Presto provides wire and fusing to enable direct connection to the batteries. However, just forward of where I mounted the HPU is the main disconnect panel and it has an open space for a large circuit breaker (200 Amp dual pole in this case) for a swim platform and an unused terminal for a gainplank/davit on the underside of the panel. Additionally, getting the wiring from the HPU to the panel was a simple routing under the floor with the convenience of the strut access hatch right there. I did, however, increase the wire size from the supplied 6 gauge to 2/0.

 

[Carpediem44DB]

Tom, Is the anodized block on the right a manual pump or a flow divider to ensure the two lift halves operate at the same evenly. I began the project of building one and have the prototype parts cut out and ready to begin the build. I bought a HPU with dual action and was going to simply parallel the two cylinders and wondering if the imbalance would be an issue that I would need to mitigate with some sort of regulator. I put a pin in the project to concentrate on other more pressing issues for now. I was looking forward to seeing your installation and commentary, thanks for sharing.
Rusty

 

[ttmott]

Lift Assembly Mock-Up and Layout -
Have you ever drilled holes in your boat? How about 24 holes? Nerve racking.
Anyhow, first is to layout where the lift assemblies mount on the swim platform. In my case I wanted to mount over where the existing chalks were. The Presto lift requires a minimum of 1-inch clearance when deployed between the lift J-brackets and the boat's rub rail. I had 1 1/2 inch clearance when I mocked it up. Then I found the swim platform has quite a crown in it, no doubt to provide for water drainage. Well this required some shims to be made which I made from Delrin. I modeled the shim then set up a fixture on my mill and milled the shims. The shims also provide a seal for the existing groove in the deck that the chalks were mounted. Then I aligned the shims and lift assemblies on the swim platform and laid out the holes to be drilled and drilled 20 3/8-inch diameter holes. One problem however, under the deck are glassed-in metal beams; of course eight of the bolt holes went right through those beams making for much longer bolts. McMaster-Carr loves me.... All of the fasteners and fittings are 316 Stainless Steel.

 

[ttmott]

Tom, Is the anodized block on the right a manual pump or a flow divider to ensure the two lift halves operate at the same evenly. I began the project of building one and have the prototype parts cut out and ready to begin the build. I bought a HPU with dual action and was going to simply parallel the two cylinders and wondering if the imbalance would be an issue that I would need to mitigate with some sort of regulator. I put a pin in the project to concentrate on other more pressing issues for now. I was looking forward to seeing your installation and commentary, thanks for sharing.
Rusty

It is a flow divider which is essential. Also. I believe there are counterbalance valves in the cylinders.

 

[ocgrant]

Looking good... Must be nice to have a Bridgeport in your garage. What esle do you have in that workshop a 5 axis mill in the corner?????

 

[ttmott]

Existing Holes and Hydraulic Fittings -
Where the existing chalks were installed holes had to be filled. I used Button Head bolts with washers sealed with Sikaflex 294UV. In fact, all of the caulking and sealant is 294UV.
The hydraulics can be supplied from a variety of locations like the deck behind the rails or back of transom or through some holes in the rail assembly. I chose through the rail assembly. The fittings are BSPP High Pressure Hydraulic so don't lose them; they are hard to find replacements. Here you can see the two hydraulic fittings and the button head screws sealing the existing chalk mounting holes and then the ten holes to mount the rail assembly. Make sure to chamfer all holes to prevent spider cracking. Pay no attention to my OSHA compliant steel toed shoes....
Oh, those two button head screws nearest to the back of the platform were right under the seals that are a part of the Delrin shims. So, those had to be removed. I put some duct tape on the underside and filled the holes with the 294UV then bedded the entire area between the gelcoat and shim in 294UV.

 

[Carpediem44DB]

It is a flow divider which is essential. Also. I believe there are counterbalance valves in the cylinders.

Thanks, do you think the flow dividers are presto's proprietor design or off the shelf units?
I wonder how a typical professional installer would handle the crown issue for a typical installation. I doubt they would mill custom shims. Nice work!
BYW, did you do the install with the boat in the water or did you pull it and do it on the hard? I understand that the prep can be done in the water but final mock up is recommended to be done on the hard. I am planning on doing mine in the water.

 

[ttmott]

Thanks, do you think the flow dividers are presto's proprietor design or off the shelf units?
I wonder how a typical professional installer would handle the crown issue for a typical installation. I doubt they would mill custom shims. Nice work!

It's all standard hydraulic stuff. In this case all European. You can get all of this stuff domestically; Parker, Rexroth, and Eaton are sources.

 

[ttmott]

The Things You Deal With -
In that back area in the 52DB are metal beams crossing the underside of the swim platform also a plywood structure that is spaced about 1/2-inch below the bottom of the deck. Well, four of the bolts for the lift assembly and the hydraulic fittings were right above that plywood. So I cut 3-inch holes through the plywood so I could access the bolts and hydraulic fittings. Then the deck thickness prohibited enough thread on the hydraulic fitting with the backing nut installed to install the hydraulic hose. So, I had to mill about 50 percent of the nut thickness away. All good now... This is a picture of that hydraulic bulkhead fitting showing not enough thread for the hose B-nut to seal.

 

[Blueone]

. What esle do you have in that workshop a 5 axis mill in the corner?????

I have one

 

[ttmott]

Bedding and Bolting the Lift Assemblies -
First to again mockup the lift assemblies with the shims and push through a couple of bolts to locate it then mask the area all around so when the bedding compound (Sikaflex 295UV) oozes out it isn't a mess all over the anti-skid. Then remove the assembly and first bed the shim in copious amounts of the 295-UV then bed over that the lift assembly using again plenty of 295-UV. Also, make sure a bead gets around each bolt and the hydraulic penetrations. Carefully set the assembly (about 70 pounds each) down over the bedding ensuring the bolt holes align. Then install and tighten all of the bolts with putting a bead of the 295-UV around the bolt head. No water getting in here... We started with the center bolts then alternated outward like torquing a cylinder head. Shown here the starboard one installed and cleaned up.

 

[ttmott]

BYW, did you do the install with the boat in the water or did you pull it and do it on the hard? I understand that the prep can be done in the water but final mock up is recommended to be done on the hard. I am planning on doing mine in the water.

In the water; no issues except had to have someone stand on the back of the lift so it didn't go tumbling overboard.

 

[Carpediem44DB]

You got my juices flowing again Tom, I have been knocking out some of the projects that took priority over a new davit so soon ill get back on it.

 

[ttmott]

Hydraulic System and First Operation
Hydraulic hoses are no problem; just route so no tight bends, out of the way, and secure so they won't chafe.
Filled up with oil.
First time up and down.
Check for any leaks.

 

[ocgrant]

Nice work as usual Tom!!!! Can't wait to see it loaded up.

 

[ttmott]

Fitting the Dinghy and Testing
Man, this lift is smooth. I can move the lift and the tender on it out on the rails with barely a push.
I've still some "fine tuning" to do on the chalks but things look great. The little boat needs to be two or three feet longer to really fit well.
As a test I stood in the boat and lifted myself out of the water; didn't even groan. Not recommended by the manuf. for safety reasons. They say to run the dinghy over the lift and raise the lift until the dinghy is stable then step out.
One thing I noticed is there are some pinch points in the lift system which will definitely lop off fingers so, caution is to be observed. And yes, I also got strafed by the pelican.
Well, thats about it on this install..
Tom

 

[Carpediem44DB]

I think that is one of the most elegant davit solutions out there. It does rob some swim step space but it is just so smart to have nothing in the water. The retracting extended platforms look cool but they are so fragile and fraught with maintenance issues, especially in salt water and they cost 2 to 3 times for the initial investment and install.
Nice job Tom.
Carpe Diem

 

[Shaps]

Looks great Tom. Job Well Done!