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Replaced bunks on MFI trailer

Bruce

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I replaced the bunks on my Yamaha SX230s galvanized trailer today.

I used twenty 3/8 x 1 1/2 galvanized lag bolts and washers, 3 x 10 foot 2x6s, 300 stainless steel staples a can of marine spray glue and 32 feet of bunk carpet.

I used a 1/2 inch cordless impact to remove the old rusted lag bolts. Then I laid each of the old bunks beside its original location to use it as a guide to line up the new.

The factory uses two 10 foot and two 5 foot bunks. I cut one of the 2x6s in half to make the 5 foot lengths. My bunk carpet was in 16 foot sections. I cut off 5.5 feet. Then I applied marine spray glue to the entire backside of the carpet. I laid the 2x6 on the glue centering it as well as I could. I walked on the 2x6 to try to press it down into the glue. I then stapled the end pieces down followed by the sides. I repeated this for each of the four bunks.

Then I took each new bunk and used the old as a reference for mounting. I placed the bunk on the mounts and drilled a 5/16 hole through the mount at one end and installed a lag bolt. The factory did not use washers, I decided to. Then I moved to the opposite end, drilled a hole and installed the lag bolt and washer. This had the bunk held in alignment so I preceded to drill and install the remaining lag bolts. I verified that each bolt remained tight after installing neighboring bolts. I repeated this process for the remaining bunks.

The cost of materials was around $70. If I had bought the supplies ahead of time it would have been less than a two hour job.

I debated what kind of lumber to use and finally decided on quality spruce with few knots and kiln dried.

Here are pictures of the new bunks.

image.jpg image.jpg image.jpg image.jpg
 

jdonalds

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Nice job. I'm sure that will give you peace of mind knowing your boat is resting on new bunks properly mounted.
 

jetboater4life

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Looks good. I did mine last summer. Carpeted UBBs that is. I'll be monitoring the staples and screws I put in to hold the carpet down this summer.
 

KXCam22

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Very nice. I plan to do this in the next few weeks. What carpet did you use? My biggest issue is finding decent carpet. Best I have found is some nice berber carpet runner (with a funky pattern). The true bunk carpet I can get feels thin and cheap, even the very expensive stuff. Cam.
 

jetboater4life

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@KXCam22 I went with this stuff for the carpet
http://www.ebay.com/itm/BLACK-12-x-25-B ... 2ec8f60381
I think it's the best stuff they had and seems very durable. 25' wasn't long enough so instead of ordering through ebay, I called them up and placed a phone order for 30'. You'll need more for a 23/24 foot boat. Price was just under $40.
 

Bruce

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I bought the carpet from a local marine shop. It was $1 a foot. I originally planned to order from @jetboater4life's eBay contact but I bought locally to be able to complete the project today. If it needs replacing in a few years I will know what I need and that it will be an easy job.
 

jetboater4life

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@MikeyL deserves the credit for that link. He posted it up on the other board and I'm glad he did. It was better than what I could get in the stores around here.
 

MikeyL

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@MikeyL deserves the credit for that link. He posted it up on the other board and I'm glad he did. It was better than what I could get in the stores around here.
Thanks for your VERY kind words.
==> http://www.ebay.com/itm/BLACK-12-x-25-Boat-PWC-Trailer-Bunk-Board-Carpet-Easy-cut-install-/200940061569?pt=Boat_Parts_Accessories_Gear&vxp=mtr&hash=item2ec8f60381
Happy to do it !
Happy Memorial Day to all ........... AIn't it so AWESOME to have REAL FRIENDS like we all do here !
Yooooooooooooooo Babeeeeeeeeeeeee !
Mikey (and Barbie) Lulejian - Lake Oconee, GA
 
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Ronnie

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Great write up and discussion topic Bruce. Also, compliments on have the tools and skill to do the job. This just started my mod list for next year, "carpeted UBBs". That just sounds expensive but I know how important the trailer and all systems on it are to the whole boating experience.
 

jetboater4life

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Great write up and discussion topic Bruce. Also, compliments on have the tools and skill to do the job. This just started my mod list for next year, "carpeted UBBs". That just sounds expensive but I know how important the trailer and all systems on it are to the whole boating experience.
@Ronnie It was not what I originally intended to do :(. I put the UBBs on (without carpet) and a few weeks later took a long trip up North with the boat. My Gelcoat started melting around the contact points between hull and UBB from what I believe to be small movements in the boat going over potholes and such. Any kind of dust or dirt would cause a sand paper action between the two hard surfaces. My bowstop was welded and I had boat buckles tight on both the bow and stern so the boat was as tight as could be, however I still think large bumps cause a tiny shift between hull and bunk. I put the carpet over the UBBs because I believe it acts like a buffer to the sand and dirt that might reside on the bunk surface.
 

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I notice you have some rust developing on your joints and along the axles @Bruce . You can keep that controlled by periodic use of a cold zinc galvanizing spray paint. It is NOT silver or gray paint, it is zinc rich paint that will put more zinc in on the galvanized trailer.

Hot-dip galvanizing (HDG), is the process whereby fabricated steel, structural steel, castings, or small parts, including fasteners, are immersed in a kettle or vat of molten zinc, resulting in a metallurgical bonded alloy coating that protects the steel from corrosion.

Steel is galvanized post-fabrication and generally en-route to the project site. The galvanizing process consists of moving the steel through various ‘baths’. The first bath ensures the steel is free of grease, dirt and oil and following this it is neutralized, then dipped in an acid bath to remove any oxidation. To prevent further oxidation and prepare the steel for actual galvanizing, the steel goes through another chemical mixture before arriving at the zinc kettle.

The zinc kettle contains 99% pure molten zinc, heated between 815 and 850F. Once the steel is dipped into the kettle the chemical reaction occurs naturally and once the base metal reaches the same temperature as the molten zinc it is complete. There is no cure time needed although each batch is typically dipped into a vat of water for cooling.

When I had the anchors done, they always looked different than the big light poles they had in the yard that had been done for the transportation department. I was told it was because the modeled pattern that hot dipping creates on a flat surface doesn't react the same on welds, corners, cuts, and between different metal components. So they use the spray to touch up. They even make mistakes and will grind off the hot dip and then retouch with the paint. It isn't as permanent, but it is the same principle in the way that zinc protects. It is a sacrificial anode, and it will wear down with exposure. That is what is happening on your trailer. It had thin spots in the zinc when it was hot dipped. If you spray those just like paint, with several coats, it will add years of service life to your trailer and other galvanized components. It is just another routine maintenance and something to do to all of your galvanized products.

Here is a link to the cold galvanizing spray at HD.
http://www.homedepot.com/p/Rust-Oleum-Professional-15-oz-Flat-Gray-Cold-Galvanizing-Compound-7585838/100142963
And a picture of the product...
86dc3925-8722-45f1-82c4-df7d440fa080_400.jpg
This is a flat paint that will better match the weathered appearance of your trailer. They also make it in bright, but that will stand out on a weathered trailer, so not really what your after. I used the bright on my anchor touch up, because it better matched the new galvanization. But it will wear and the flat then is better for maintenance.
 

Julian

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KXCam22

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I put new bunks on my trailer yesterday. The install went quickly with one son with the air impact taking them off and me and the other son putting them on. Took about 45 minutes. After some research, I used regular pine (for the strength) and treated it with thompsons water seal. Used a 1/2" round router bit to round the edges of the wood. Home depot grey marine carpet, galvanized staples and lag bolts. I put two layers of carpet down, the first with glue. I put 4200 on the lag bolt threads to seal against water penetration. I only partially tightened the lag bolts and then tighten them fully with the boat on the trailer, using the weight of the boat to force them into place. I treated the bunk carpet with a few coats of my elixir of choice, which is cheap automotive silicone spray. On a side note: I tested silicone spray, rain-x fast wax and maxima clear-coat (a type of silicone) on some carpet scraps to see which one made them the slipperiest and lasted the longest. I had high hopes for the rain-x wax but the cheap silicone spray worked and lasted the best. Cam.
 

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This QUALITY Boat bunk carpeting seller on eBAY ........ is still alive and well.

http://www.ebay.com/itm/BLACK-12-x-25-Boat-PWC-Trailer-Bunk-Board-Carpet-Easy-cut-install-/200940061569?pt=Boat_Parts_Accessories_Gear&vxp=mtr&hash=item2ec8f60381

And his prices cannot be beat. And neither you beat the QUALITY of his product.
It's manufactured in Dalton, GA - "The carpet capitol of the world."
Strongly Suggested !!!!!!!!
Mikey Lulejian - Lake Oconee, GA

PS - Also, using stainless steel staples, hopefully inserted with a "powered" stapler is the only way to go.
FAST and most importantly, EAS-Z !!!!!!!!!!
 

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@Bruce and anyone who did NOT use pressure treated wood. Why not?

Additionally, should bunks be installed cup up or down? I'm guessing down but just wanted other opinions.
 

Bruce

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@Bruce and anyone who did NOT use pressure treated wood. Why not?
I read a lot of opinions on what to use. Treated lumber should last longer but it can cause corrosion. I used spruce. It is straight and does not have much if any cup and does not leak sap. I decided that bunks are cheap and easy to replace so why worry about using treated. Also the untreated lumber in the factory bunks had lasted longer than the carpet.
 

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I was also like Bruce. I did a lot of research. Here are my thoughts.

Wood: PT wood is very poor quality #2 or #3 grade wood and warps quickly. I bought some last year to make bunks with and they warped to be unusable before I got around to making the bunks. Also with treated you have to be careful of the fastener metalurgy. I debated cedar (not strong enough), fir (best but hard to find as our wood is graded SPF "spruce or pine or fir" so you dont know what you are going to get. I settled on some nice dense blue beetle kill #1 pine then used the thompsons to seal it against water penetration. Besides, the bunks truly don't spend that much time in the water and its the carpet that holds the moisture against the wood.
I also debated making the bunks wider (2x8) but there are chines on the hull that could have hit. I did make them longer where it counts. I read that untreated Cyprus wood makes the best bunks and that is what the boat manufacturers use. I did not recognize the grain of the wood that came off the MFI trailer so that could be what it was. We don't have native cyprus trees in Canada. It looked like laminated plywood.

Staples and Lags: I could have used stainless staples and lag bolts but the original staples had no rust and the original lags were only plated (not galvanized) and had lasted good. Besides, I couldn't find SS staples to fit any of my air staplers without buying 20,000. On my old bunks the wood, lags and staples also lasted longer than the carpet.

Carpet: I search far and wide for good carpet and looked at quite a bit of "marine" and purpose made "bunk" carpet. All of what I looked at was thin and inferior, and some was very expensive - up to $250 to carpet the bunks. The home depot oelfin marine carpet is thick and has a better backing than all the stuff I looked at. I almost used a very nice berber carpet runner that had a nice funky pattern.

I hope this helps someone. I will be able to give you the exact definitive answer (that this was the right approach) in 6 or more years. Cam.
 

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Scottintexas

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added to the FAQ under trailers,
 

Ronnie

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I just started this process for my 2010 MFI boat trailer and 2006 waverunner trailer.
Got the carpet off the shelf from West Marine. Could have done both trailers with half of what I bought but would not have been able to completely cover both sets of bunks, just one side of each bunk or the other. I don't see any reason to cover the bottom side but they come from the factory like that and others seems to continue the practice when replacing their bunks so I decided to do the same. About $150 for carpet ($50 for each big roll for the MFI trailer, $25 for each little roll for the waverunner trailer). Interestingly, West Marine had a set of 2"x4"x48" bunks ready to go for $74 a pair (my waverunner trailer uses 72" bunks).

IMG_0971.JPG

I also bought the wood (pressure treated), $11 per plank x 3 ($6 per 2"x4") and 1.5" SS lag screws along with SS staples from Home Depot. FYI at West Marine the lag screws were $2.50 each and at Home Depot $1.40 (take $1 or more off for galvanized instead of SS, I was tempted but am hoping to avaoid replacing bunks again for as many years as possible so the pic of my current galvanized lags screws reminded me not to go economy on this.
IMG_0972.JPG
I will probably need more spray on glue than I currently have so I will be making another trip their soon.
IMG_0969.JPG
The big screw came out of the boat trailer bunk the small one from the waverunner trailer. I am using the bigger screws on both trailers this time around and am not sure why the manufacturer or previous/original owner went smaller in the first place.

By the way the SS bolt in the pic is from my son's waverunner. That is, it is one of the two of four remaining (noticed the rear two were missing when I pulled a sample bunk board screw) that I brought as a sample to purchase more of from West Marine.
 

Scottintexas

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