New issue cropped up on my transom/bunk position!

[Expidia]

Last season I noticed the left bottom of the transom was buckling.
I orignally set up my rig back in 2007 with help here from the forum as to transom positioning on the bunks and the correct tongue weight on the hitch ball.

Now the transom is starting to buckle. Any suggestions to lessen this?
Moving the boat forward will not change anything.
Moving the boat back with the edge off the transom is the only solution I can see.

I thought of maybe something like adding a roller on each side of the bunk to take some of pressure off on the transom?

I've always used a transom saver and this Yamaha 40 that I upgraded to in 2020 from a Merc is one of the lightest out there at only 214 lbs.

Suggestions?

 

[alldodge]

Those ratchet straps can put a whole lot of force pulling toward the trailer.

 

[briangcc]

Get ahold of Lund, they're still in business, and see what they say. My hunch is they're going to tell you to slide the bunks in an inch or two because that's where the floor stringers are - I'm going off the rivets in the transom.

I'd also question the white goop on the transom near the drain plug.

 

[Expidia]

Get ahold of Lund, they're still in business, and see what they say. My hunch is they're going to tell you to slide the bunks in an inch or two because that's where the floor stringers are - I'm going off the rivets in the transom.

I'd also question the white goop on the transom near the drain plug.

The goop is 3M Urethane Seam Sealer. I had some drips along that edge in two places when I filled the boat 1/2 way up with a garden hose but my welding guy said it can't be welded there as there is a rubber gasket along that edge. He said to use some of that sealer as it does not harden. It's worked over the past * 5 years, but I'm going to scrape it off and apply Gluvit that my boat dealer recommended.

*At least I thought it was working . . . I frequently look over the side of the boat while under way at the bilge pump outlet while running the pump. No water, yep dry as a bone! Then two years ago I had a local boat dealer (where I bought my 2nd outboard) install a new bilge pump (old one was 15 years old).
Past two years bone dry . . . NOPE! On the boat ramp the boat was on an angle and I pulled the plug and like 20 gal of water came out. Come to find out the dealers useless mechanic NEVER attached the bilge pump outlet hose to the bilge pump (or it fell off if he never tightened it). So past two seasons I've been running with 10-20 gals of water under the floor. I do wash the entire deck down from time to time, but I crank the front up high on the 3rd wheel and let the water run out of the transom plug. So I never knew I was taking on water over the season when docked or sitting in a cove because I could always hear the pump running

This is the problem today. No one test drives your car like after a brake job or installing new tires. All this guy had to do was dump a bucket of water in the bilge to test the pump after he installed it. Instead he put my family at risk with no working bilge pump over the past two years.

Moving the bunks might be feasible (just the suggestion I was looking for Brian). I'll bring my sockets and wrenches next time I launch the boat and see if I can move the bunks under the stringers in the parking area.

The original dealer I bought the boat from had set up the outboard incorrectly as to the height and also the position of the boat on the bunks fore and aft.

 

[Expidia]

Those ratchet straps can put a whole lot of force pulling toward the trailer.

Maybe so, but I don't crank them to their tightest click. They don't have to be. They are only there to hold the boat from sliding off the trailer on a turn or holding the boat onto the trailer during hard braking or an accident.

I think Brian's post #3 might be right on the money in that the bunks should have been positoned under the stringers when the dealer installed the boat on the trailer 17 years ago.

I don't think the other side is buckling because there is a large nylon block mounted over that bunk giving that area more support.

 

[dingbat]

I have a glass boat, but builder was insistent that the bunks be position directly under the stringers.

Sent me a drawing where the bunks should be positioned relative to the boat

 

[airshot]

How much weight is in or on that transom ? Looks to me like bunk should have been wider or you need another bunk. Overtime transom strap could cause that. Is the trailer to stiff/ no suspension ?? Been around aluminum boats for over 60 years and never ran across that before, definitely a problem !!

 

[cyclops222]

The left side of the transom bottom is being crushed by water rotted wood inside of the transom. It should be the same thing on the right side of the transom bottom. behind that massive white plate. Old boats do die.

 

[airshot]

The left side of the transom bottom is being crushed by water rotted wood inside of the transom. It should be the same thing on the right side of the transom bottom. behind that massive white plate. Old boats do die.

If I am not mistaken, that is an aluminum boat, no wood support down there.
Looks more like a trailer with no suspension and a cranked down rachet strap that beat and crushed the hull.

 

[Expidia]

If I am not mistaken, that is an aluminum boat, no wood support down there.
Looks more like a trailer with no suspension and a cranked down rachet strap that beat and crushed the hull.

Trailer has springs. Straps never racheted full. Only need to keep boat from sliding left and right. And forward in a frontal accident.

 

[airshot]

Trailer has springs. Straps never racheted full. Only need to keep boat from sliding left and right. And forward in a frontal accident.

If the springs are worn or collapsed or way to stiff the hull will get beat on going down bumpy roads. In my 60 yrs I have saw this on occasion with trailers that are to stiff or poor springs. Not common but it happens. Often people use a wider board for the bunk to spread out the load. Unless the hull is weakened from corrosion or a heavy load is carried inside near the transom, a Lund boat should not do that, nor would any quality aluminum hull boat.

 

[Expidia]

Thx airshot. I’m going to swing by the only Lund dealer in my area and see what they say. The only item in that area is a 6.5 gal plastic gas tank which sits higher up in the gas locker.

I’m going to float the boat and adjust the trailer in the parking lot to move the bunks in like 3 inches to be under the stringers.

My only concern is I might widen the buckling area towards the right.

 

[airshot]

Are you referring to the " strakes" the long rib running front to back as stringers ?? According to most all aluminum boat mfgrs, do not put the strakes onto the bunks, the bunks need to be inside or outside of these strakes. Some folks even add some type of padding under the carpet covering the bunks to create a bit of a cushion and protect from scratching. Based on your pics only, it appears the boat was forced down onto that bunk or mabey bounced up and down causing that dent. Interested to see what Lund says.....has a strap ever came unhooked where the boat could jump up and down on the trailer going down a bumpy road ?? Wish I could help more!

 

[cyclops222]

Almost every Aluminum boat with small OB on them. Do put a piece of Marine grade plywood between the outside transom skin and the inside transom Aluminum skin.
That piece of plywood SPREADS out all the bending & twisting stresses of the motor ay W O T.

 

[alldodge]

Almost every Aluminum boat with small OB on them. Do put a piece of Marine grade plywood between the outside transom skin and the inside transom Aluminum skin.
That piece of plywood SPREADS out all the bending & twisting stresses of the motor ay W O T.

Your saying buy a brand new boat and then modify it?

 

[FLATHEAD]

Almost every Aluminum boat with small OB on them. Do put a piece of Marine grade plywood between the outside transom skin and the inside transom Aluminum skin.

Not exactly true especially with more modern boats. Not sure how old the OP boat is. I have a 5 year old aluminum boat without so much as a toothpick worth of wood in the construction.
I’d say that is from cranking down the straps way to tight worrying about it being super secure.

 

[Expidia]

Are you referring to the " strakes" the long rib running front to back as stringers ?? According to most all aluminum boat mfgrs, do not put the strakes onto the bunks, the bunks need to be inside or outside of these strakes. Some folks even add some type of padding under the carpet covering the bunks to create a bit of a cushion and protect from scratching. Based on your pics only, it appears the boat was forced down onto that bunk or mabey bounced up and down causing that dent. Interested to see what Lund says.....has a strap ever came unhooked where the boat could jump up and down on the trailer going down a bumpy road ?? Wish I could help more!

You can see how frustrating it is to get opposite opinions on the positioning of the bunks under the hull. I was going to position them over the stringers which would be only like a 3 inch move from where they are now. Now you have me hesitating to do so.

The right side lower transom is fine, so I'm inclined to think I might have hit a pothole while towing the boat. The trailer is not a high end one with springs and brakes. It's more of a utility grade (cheap Shorelander trailer).
It is not a cushioned ride because the boat, gear and outboard don't weigh that much. It uses leaf springs where the boat would have to be a lot heavier to sink down into a springier area of the leaf springs. I've weighed the total rig with gear on a trucking scale and it came in around 1,650 lbs. This way I could adjust the hitch ball weight to like 5-10% of the total weight.The boat more or less just sits there ontop of the springs.

I'm thinking I could jack the boat a little off the bunk, then place a 2 x 4 with a rubber non slip sheet between the board and the transom and give the 2 x 4 a few whacks with a sledge hammer to push the bulge back in place. I'd also jack up the motor a little to take the weight off the transom while i'm trying to remove the bulge.

My concern is that I'm dealing with aluminium and the more I flex it the more I might be weakening it. Also it's just above the seam. If I whack at it I might start that seam leaking. I'm also thinking to just leave it alone as is.

If I try and contact Lund customer service like I did for another issue years ago I think they just refer your to their dealer network.

I'll also go around with the rig to a few boat dealers and try and get other opinions and try and get a referral of someone who does restorations. At this point the brand doesn't matter. Anyone experienced could repair or replace the outside aluminum of the transom and fix the lower bulge. This rig, I've always kept it garaged and in pristine condition. And upgraded from the original Mercury 40 hp (which I got 12 years out of it) to a Yamaha 40 hp (max for this rig) 4 years ago in 2020. I wanted to renew the outboard just for the reliabilty aspect of a new outboard. These newer Yammies are a dream!

I have a Lund dealer a 20 min drive away, but I don't know how versed they are in repair or aluminium restorations. I think they just sell a few Lunds as a sideline.

 

[airshot]

Not sure I would try fixing that bulge either, especially if it isn't hurting anything or leaking. Sooner or later our boats will get some boo-boos, we just live with them. I would consider using some covered 2x6 to spread out the load bearing surface. You could always remove a leaf in the springs to soften the ride a little. My own 40 hp Merc classic runs and looks like new, in fact it runs so good I would trust it over one of the new mechcanical wizards on the market. I prefer to keep things simple....

 

[Expidia]

Not exactly true especially with more modern boats. Not sure how old the OP boat is. I have a 5 year old aluminum boat without so much as a toothpick worth of wood in the construction.
I’d say that is from cranking down the straps way to tight worrying about it being super secure.

Once again which I've mentioned in previous posts above. There was never any need to crank down those straps tight. I always just ratchet down to snug so the straps are not flapping around. Boat is 17 years old. But always has a custom made trailer cover on and has always been garaged.

I'm more inclined to think the buckling or pressure bulge is not a result of wood rotting inside the transom. I'm thinking it was proably a result of hitting a pot hole last season while trailering, since the other side is fine. I do think the transom has wood in it becasue I can see what appears to be wood through the small hole I'm about to patch with some Marine-Tex until I can find someone capable of replacing the outside aluminium of the transom which is showing some corrosion bubbling under the paint in a few spots.

They say aluminum doesn't rust . . . Yup, it just corrodes

 

[airshot]

Even if you have wood in the transom, there would not be any along the bottom where the bulge is. Wood is typically up near the top if any.