transom extension and trailer bunk redo

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handyandy
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transom extension and trailer bunk redo

Post by handyandy »

So my boat was short shaft 16" transom, and it started with a 40 prop tiller I ran for few years. Then added a jack plate which helped with shallow water capabilities, but I really wanted a jet. Then almost two years ago I swapped to a 1993 60hp tiller short shaft prop mercury with intentions of making it jet. I hunted down a jet lower for it that I got second hand for a good price. Swapped out the long shaft drive shaft of the jet lower I got for a short one mounted it up on the engine and have been running it with the mecury made 60/40 jet for a while now. It wasn't bad it's a good running engine pushed the boat well hasn't really given me any troubles.

But when I first swapped the mercury I wanted a omc three cylinder. But at the time when I first wanted to swap to a jet I couldn't find any omc 56ci triples with a tiller. Or any non tillers cheap to convert to tiller. I came across the merc for a pretty good price and got the jet drive for it pretty cheap. But back around thanksgiving I found a ok deal on a really clean 1994 omc 70hp tiller with a jet already. I ended up buying it and left the mercury on through the waterfowl season as I didn't want the boat decommissioned for the swap during waterfowl season. So I started the swap about three weeks ago. It was a little more involved than just unbolting and swapping engines as the evinrude is a long shaft, so I had to weld up a extension for my transom. My trailer bunks had also seen better days so I figured I'd redo those as well while I was at it when I had the engine off.

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handyandy
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transom extension and trailer bunk redo

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To start with I unbolted the mercury and lifted it off the back using a shop crane didn't photograph this as it's pretty straight forward unhook battery cables, unhook fuel line, loosen bolts support engine using engine hoist and lifting straps. With the help of a friend unbolt it and remove it carefully. Then I unbolted my jack plate. With the engine off I jacked the boat up slightly off the trailer on one end using a car jack with a block wood between it and the boat. Once the end of the boat was off the trailer bunks I slid pieces of 2x4 wood scraps between the bunks and hull to leave a gap between the bunks and hull. I then did the same on other end of the boat. I then slid long heavy duty tow straps between the hull and trailer. I have two post car lift in my garage so I backed the trailer in and positioned the lifting arms appropriately and hooked the straps to them to lift the hull off the trailer. Sorry I didn't think to take pics of the wood between the hull and trailer bunks and putting the lifting straps in.
Attachments
IMG_1631.JPG
underside of boat some decent dents hard to see in my crappy pics
underside of boat some decent dents hard to see in my crappy pics
boat just lifted off
boat just lifted off
IMG_1635.JPG

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handyandy
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transom extension and trailer bunk redo

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After getting it off the trailer I started removing the old bunks which were pretty warped and bowed and crappy. Part of my problem was the trailer only had cross members at the front in back to support the bunks no middle cross member to keep them from sagging and bowing in the middle. So middle crossmemember was one I made up using some old square tubing I had lying around. I measured it up welded it together fit it on the trailer then welded it on the trailer.

The welders I have are a lincoln square wave tig 175 that I bought used a while back 5-6 years which has been really good to me. I taught myself tig weld using it back in college, for home shop/hobbiest it's a great machine I've had zero issues with it. The MIG welder I have which I just bought a few months ago is a Hobart 190 that came with a spool gun. I can't say enough good about it. It's no industrial commercial shop welder but for the money you can't beat it I highly recommend it. I looked at every kind of mig and looked for used deals before pulling the trigger on it. It mig welds steel great thin and thick, and the spool gun works great. I was somewhat hesitant about getting it over the miller equivalent as the miller is lighter being inverter powered and has infinite variable adjustment for the voltage where as the hobart is transformer powered making it heavier and has 9 fixed variable voltage settings. The hobart is much cheaper though I bought mine through northern tool using a coupon for 700 something and it came with the spool gun. The Miller 210 which is about the equivalent is over a 1000 not including a spool gun. I didn't consider the lincoln welders in these smaller home shop migs as they are made in mexico and cost about the same. I wasn't going to pay about the same money for foreign labor that just me though lincoln makes good products I have nothing against them obviously since my tig is a lincoln machine.

Enough about welders here are some pics of the trailer after getting the bunks off and welded in the new middle crossmember. Sorry I didn't take a ton a photos I'm no photo journalist just thought I'd make this post anyways in hopes it might help others.
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IMG_1633.JPG
IMG_1632.JPG

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handyandy
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transom extension and trailer bunk redo

Post by handyandy »

After I got the new cross member in I proceeded to cut pieces of some old plate steel I had to weld them on for trailer bunk mounting tabs. My trailer initially had two bunks I made into a four bunk trailer now so I moved my outer mounting tabs out few inches and added some more towards the centers for two more additional bunks closer to the middle of the trailer. Four is over kill considering my boat is a 1554, but I figured spreading the weight of hull out over more surface area while being trailered and going down bumpy roads wouldn't hurt anything. Rather it be overbuilt than under built.
Attachments
IMG_1640.JPG
IMG_1639.JPG
used a piece of rectangular aluminum tubing I had lying around to make sure my bunks were all sitting pretty level across.
used a piece of rectangular aluminum tubing I had lying around to make sure my bunks were all sitting pretty level across.

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handyandy
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transom extension and trailer bunk redo

Post by handyandy »

For the new bunks I used pressure treated 2x4 that were twelve feet long cut down to the length of the originals which was around 11ft long. I used stainless bolts to afix them to the mounting plates I welded on the trailer. Once I had the bunks bolted down a leveled out well I screwed pieces of the trek decking on top of them that the boat will sit on. This stuff is pretty slick allowing the boat to unload easily a friend of mine with a mud boat did his bunks with I liked enough I decided to use it won't rot and won't hold moisture like carpet does so the wooden bunks should last longer. I bought three 8ft pieces of the 4" wide gray trek it was the cheapest I ripped each piece in half down the middle long ways to make thinner strips that covered the tops of the 2x4 wooden bunks perfectly. I used a table saw to rip them down it cut about the same as wood does just had to go a little slower cutting being it's denser. I screwed down the trek pieces using stainless deck screws. I counter sunk all the screws into the trek so they wouldn't scratch the bottom of the hull.
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the stainless screws I used
the stainless screws I used
picture of the trek screwed down
picture of the trek screwed down

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handyandy
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transom extension and trailer bunk redo

Post by handyandy »

After getting the bunks done I set the boat back on the trailer and got started on the transom extension work. My boat is a excel that was painted with what is like a thinner version of line x or rhino lining. It was sprayed in and has held up great but was a pain in the arse to get stripped off where I was going to have to weld. I started by using my tig welder to weld up and fill in all the old holes from previous engines that have been on this hull. There were bolt holes still from the mud motor this hull originally came with then holes from having outboard on it after that. I bought it used and it had a 40hp prop tiller outboard on it when I got it. I used heavy duty wire wheel cup on my grinder to remove the paint/coating on the boat from around the holes then a sand flapper wheel to clean up the aluminum a little further then a stainless wire brush. When welding aluminum getting it clean is imperative to getting good welds steel is much more forgiving in terms of welding if contaminates are present. Once the holes were cleaned up I started welding them shut. Then ground them smooth after welding.
Attachments
transom before anything was done
transom before anything was done
transom before anything was done
transom before anything was done
holes all cleaned up for welding
holes all cleaned up for welding
this is after all the holes were welded and smoothed out.
this is after all the holes were welded and smoothed out.

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handyandy
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transom extension and trailer bunk redo

Post by handyandy »

After the holes were all welded shut I had to strip off and clean up the top of transom to be able to weld a extension on it. I used a piece of 3/16" wall 2" x 4" rectangular tubing for my extension. I had to make small angle cuts on the bottom of the rectangular tubing to fit the transom just right. I used a band saw to make those cuts to get it to fit well. Once it fit well I cleaned up the top of the transom and the extension with a SS wire brush to weld extension piece on to the transom using the spool gun. I started by tacking the extension on at each corner and in the middle on the inside of the boat and the back. to weld it fully I made passes welding about 3" at a time to avoid getting to much heat in one area and warping it. After making a pass on one spot I'd move to the other end of the opposite side of the extension to make another pass then would let it cool and take a beer brake.
Attachments
top of transom after wire wheeling off the boats paint/coating stuff was tuff really had stick it to it with a coarse wire wheel cup on the grinder.
top of transom after wire wheeling off the boats paint/coating stuff was tuff really had stick it to it with a coarse wire wheel cup on the grinder.
the extension cut to fit the transom
the extension cut to fit the transom
closer view of one of the ends of the extension that needed to be cut to fit the existing transom angles
closer view of one of the ends of the extension that needed to be cut to fit the existing transom angles
back fully welded
back fully welded
one spot after making a pass
one spot after making a pass
inside all welded up
inside all welded up
fully welded up on the inside
fully welded up on the inside

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handyandy
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transom extension and trailer bunk redo

Post by handyandy »

Sorry I miss labeled the pics of the inside thats after making a few passes I did weld it fully across on the inside as well. Before everyone ask why I didn't use a longer piece of rectangular tubing that could span the full width of the transom it's because I got that piece for free from work as left over scrap piece. At some point I might get some sheet aluminum or other pieces of rectangular tubing so the extension goes across the whole width but it really doesn't matter as it would more for aesthetics than anything else after the extension was fully welded it is plenty strong.

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handyandy
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transom extension and trailer bunk redo

Post by handyandy »

After the extension was fully welded I cleaned it up using a flapper wheel and lighter stainless steel wire wheel on the grinder to prep it for paint. I sprayed it with parkers duck boat primer, then coated over it with herculiner to try and match the truck bed like coating this thing was originally painted with. I then painted over the herculiner with flat rattle can camo paint and used some stencils a friend had from painting his boat to try and match the original camo pattern as best I could. It's not spot on but close enough for and turned out pretty well I think.
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IMG_1670.JPG
IMG_1669.JPG

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handyandy
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transom extension and trailer bunk redo

Post by handyandy »

After the paint cured and I think after it gets faded some and dirt on it, it will match the old paint on the boat pretty well. But once it cured I proceeded to mount the jack plate back on, then bolted the engine back up. I used some welding vise grip clamps to hold the jack plate in place centered on the transom to drill the holes. I used some silicon to seal up the bolt holes going through the transom. Used the engine hoist and got help from a friend to get the motor hung on the jack plate.
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motor on the stand
motor on the stand
mounted up
mounted up
IMG_1681.JPG

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handyandy
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transom extension and trailer bunk redo

Post by handyandy »

So for the people that are curious why I made the swap when I had/ still have the old engine that ran fine. It's kind of like when your chevy guy and your driving a ford cause you got a good deal on it. Even if the ford truck is fine you still want a chevy and end up buying a chevy once you find a deal on one. I'm a omc guy and the 56ci omc triple two strokes were and still are arguably one of the best outboards in this size range. They just run faster than any other outboard in this size range with a jet. At some point I'll probably pull the reeds and clean up the reed cage and put chris carson reeds in and maybe shave the head down some. Going to run it as it for now though. For now I still have the merc sitting in my garage debating if I want to hang on to it or sell it. Don't know why I wanna hang on to it but I kind of want to as it's one of the better engines merc made. Only better engine merc made in this size range was the 1998 and later two strokes that were 59ci vs mine that is around 52ci. I'm biased and don't consider any four stroke superior to these two strokes in these mid range outboards. The four strokes are much better than they use to be but when mercury has to cut down the new stainless impellers in the 60/40 jets so the four stroke can turn them better that says something, when the two strokes turned them just fine. Something about triple two strokes just work well and I'm partial to two strokes and have a hard time letting go of good engines even if I'm not using them. I'll probably clean it up maybe touch the paint up and sell it once I get tired of up taking up space. Haven't had a chance to run the boat yet with the omc as I just got it bolted up and set the height last night. I will post up results once I have them.

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handyandy
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transom extension and trailer bunk redo

Post by handyandy »

Also while doing this I swapped my trolling motor from the motorguide that took a dump on me to a minnkota powerdrive V2 55lb thrust I scored off the list for pretty cheap in like new shape. It has autopilot and the built in transducer I want to get the ipilot remote for it. Hopefully it will last longer than my motorguide did. I have a new garmin fish finder with down scan I still need to put in and will probably hook my old fish finder up to the minnkota's transducer and have one up front as well. This may not have been a huge project swapping a jet ski power plant in a jon boat but I thought it was a relevant one for anyone that may be considering swapping to a jet. As jet outboards need to run about 6" higher than their prop counterparts, and making a transom extension is something you would have to do. Unless you had a tall transom with a prop a put on a short shaft outboard jet engine. I went ahead and threw in the trailer redo as well since I was at thought maybe someone might like it.

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richg99
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transom extension and trailer bunk redo

Post by richg99 »

Wow...Lots of work and a well-told story. If anyone else is going to do something similar, you've given them a great plan to follow.

The only thing that I picked up was that you used "treated lumber" for your bunks. Treated lumber has been known to corrode the crap out of an aluminum hull.

You, though, may have avoided some of the issues by using the Trex between the treated and the hull itself. Only time will tell.

thanks for posting richg99

CedarRiverScooter
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transom extension and trailer bunk redo

Post by CedarRiverScooter »

Great job with the transom extension!

Maybe add center gussets down to the existing knee brace? Would be an easy rivet job.

lckstckn2smknbrls
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transom extension and trailer bunk redo

Post by lckstckn2smknbrls »

I too was concerned when you said your new bunks are pressure treated. The composite decking should work as a barrier in between the pressure treated wood and the aluminum hull. Just keep an eye on it.
1971 14' Ward's Sea King Jon Boat / 1983 Mariner 25HP

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