Pour in transom replacement

[larboc]

*cross posted from the "other place"*


Seacast, Arjay 6011, Nida, etc.




The bottom of my transom is shot in this boat, way too hard to split the deck to get access from the top and full inside access so I'm considering filling it up with seacast. I already went in through the I/O hole and used an auger bit to remove the wood in the center section of the transom, but the outer sections are angled enough that I can't get a bit in there. I used a pressure washer to blast out the trim tab holes and they are all connected (entire bottom of all transom panels are rotted out and gone). Original plywood was 3/4". The crack at to bottom of the I/O hole is of moderate concern, however I think once there is something solid behind it, it should be okay after getting vee'd out and filled with epoxy/csm.

PSA, a 15hp pressure washer with the single stream tip can delaminate fiberglass if you hit an existing hole.

Option 1: Pour it as it is, the outer sections should be fine left alone, assume the pourable will find it's way to the entire bottom of the transom. If it doesn't then inject it later.




Option 2: take an upside down "T" section out of the inner transom.




I was using this boat last year with no signs of issues, but when I was getting ready to float it this spring I noticed the crack at the bottom of the I/O.




Save the boat ownership jokes, I got it for free and I've used the hell out of this thing over the past 6 years I've owned it and it has always been a reliable fish catcher, if not the prettiest.




Looking for anyone with actual experience, I can find boyscouts on the marine forums.

 

[larboc]

Seems like 50% of free boats on CL at least around me are sterndrive and about the same size as yours.




I'd be shopping for a new free hull to stick your drive-train into. There's no way in hell you're gonna have that in the water this summer without a monumental amount of work considering it's already June.

The problem that I've noticed is that every boat I've looked at in the $0 to $10,000 range has a rotten transom to some extent but if it still "floats" the seller doesn't feel that it affects the price.

 

[larboc]

Why are transoms not made from Aluminum?

Money.




Actually some oems of nicer boats use pour in stuff now days.

 

[larboc]

What outdrive goes in there? If it’s an omc, I’d haul the thing to the junkyard. When it breaks, and it will at some point. Your screwed. Cause they went outa business decades ago. The only parts your gonna find will be off another junked outdrive. If it’s a merc, carry on. I would cut out the inside and leave a flange as was said. Get all the trashed plywood out and use a plywood form to hold the seacast in. Pull off the form and refiberglass the inside. If it is rotten. I would be worried the stringers are too.

Mercruiser 888. 188hp Ford 302 with 351 heads.




It would have already been scuttled if it was an omc.

 

[larboc]

Ive used seacast on a smaller hp boat and it worked fine. Went in carefully from the top with an electric chainsaw and dug the old wood out.

Im know its strong enough for your application but getting all of the shit wood out will be difficult. You could take part of the inner skin off clean out the rotten wood reglass it back in place and then fill with seacast. Or better yet take the back skin off since the inside is tied into the stringers and that where all the strength is on an IO. Again clear the shit wood and pour. Or do it right and use marine ply. Epoxy to the inside skin, epoxy outer skin on, reglass, fair and paint.

I don't know if I'd call fixing it with marine ply wood "right" these days. It would be cheaper, but will rot again.

IME wood has no place on a boat anymore except for cost.




I did a transom on a trihull 10+ years ago with plywood. Pain in the ass, but doable because I was able to pull the deck cap, not an option here. In hindsight I should have done a pour in on it and gone boating sooner.

 

[larboc]

Makes my heart sink to see a boat like that in June, I just unloaded 6 sheets of ply to redeck my pontoon. No experience with transom like that but Ill bet if you open it up it will be a lot more rot than you think.




15hp pressure washer??? Never saw one that big, what are the specs on it? How about a pic

Had to scrape frost off my windshield this morning, but I would have been out fishing already if this boat wasn't like this.




It was a northern tool china special in store clearance for $250. Iirc it's 4000 psi 4.5 gpm. Its beefy at full trot.

 

[larboc]

I called seacast and got put in contact with a pro who looked at the pics. He said it is odd that the OE transom plywood core was 3/4" instead of 1.5". He said that since the inside access is restricted that if they were doing it they would take the back skin off, clean out the wood, glass it back on, fill with seacast, and re gelcoat the cut.




He suggested another option would be to cut out the biggest section of the inside skin I can get to, dig the wood out of the areas I can't, cast a new fiberglass inner panel on a piece of waxed white Masonite, and glass it into place. Then pour seacast in the whole thing to make the new transom 3/4" thicker which brings it into mercruiser's spec. Originally this boat had bare pieces of plywood glassed on to get the extra thickness.




IDK what to do. Cutting the back skin off seems like a massive PITA to get right putting it back on, seems like it would weaken it at the joint, and doesn't thicken up the transom.




Inner panel section removal/rebuild is going to suck as well. I'm leaning towards this route though.

 

[larboc]

Well, I just ordered $1500 worth of seacast, accessories, and shipping. Probably nuts for sinking this kind of money and time into it but it's worth nothing as is and we use the heck out of the boat for the entire week of summer.

I've done a little boat shopping and the 2 somewhat similar boats I've looked at were $5k+ and had soft spots in the transoms.

I am of the opinion that every boat that's more than 5 years old with a wood core transom has some degree of a rot. Now I'll know 100% that mine is stronger than original and will never rot, even if nobody can see it.




My plan is to cut out as much of the inside as possible, space the removed section out to 1.5" and use bi-axial to Z it to the old part.




While it's out I'll back up all the damaged parts of the skins with a couple layers of 17oz mat backed bi-axial on the inside.




It looks like it's going to take around 15 gallons of seacast to do it all with the increased thickness over 75% of it. I'll put whatever is left towards stringers, though they seem oddly intact and solid. It's much cheaper by the 5-gallon bucket so I got 4.

Should I ever feel the need to build up a more powerful SBF for it, the transom won't be of concern.

Hopefully this doesn't bite me in the ass, but I plan to have it on the water by the 3rd of July fireworks show on the lake.

 

[larboc]

Your either going to be the biggest seacast fan or the biggest hater $1500 = wow




Good luck, I have always been interested in how that stuff works.

Almost $400 for shipping hurt a bit.




Considering the size of the transom, there really wasn't going to be a cheap wood free option. Doing it with marine plywood would have been about $1000 cheaper and probably less work, but I don't think wood belongs on a boat.

 

[larboc]

Not even teak?

Okay, I guess I should have said "anywhere structureal" although teak has its own share of maintenance needs so IDK.

 

[larboc]

Hacking away at it. The center section around the IO was 3/4" plywood, everything outward of that was 1/2" wood (balsa?) endgrain, as is the bottom of the hull. Looked like they took a 2x4 of balsa and cut it into 1/2" slices and stacked it in, then fiberglassed over. I guess it's a common wan to do it and the theory is that the resin seals the end grain so it won't rot if exposed to water. Turns out that's total B.S., several examples on the internets of boats and young as 5 years old having rotten balsa cores.

The transom inner skin is turning out to be a major PITA to get out where the core is still good. I'm having to cut it into a lot more sections than I wanted so it may end up getting a completely new inner skin rather than patching together 10 pieces.

A 12" long sawzall blade is so far working, then the pressure washer blasts the wood off the fiberglass. I tried cutting the wood with the pressure washer but it isn't really any faster than the sawzall nor does it allow for larger sections to be removed.




O, and of course as soon as I started working on this the weather got hot, grinding fiberglass in a tyvek suit in 85 degree weather sucks.

 

[larboc]

whats the plan to keep everything aligned when you done?

engine>outdrive

That's fairly straightforward. The bellhousing bolts to the inner transom plate via two rubber mounts, then then engine mounts are adjustable up and down. A friend of mine has the mercruiser tool that slides through the gimble bearing and into the drive coupler. You adjust the engine until the tool slides in easily, then wipe grease on the tool where it goes through the splines and adjust until the grease gets wiped off evenly to get it lined up even better. The rubber in the coupler takes care of the rest. If its off, then it wears the aluminum splines in the coupler out instead of taking out the shaft splines.

 

[larboc]

ive done the alignment part last year when i swapped engine in my boat

LOLs at the specs.

alignment tool has to come out easy, holding it by only 3 fingers

i meant aligning everything with the hole in the transom

i thought for some reason you removing that as well

Ahh. The hole will still be there in the outer skin. I'll wrap the I/O hole out-out with biaxial and then drill the holes back through the seacast.

 

[larboc]

Had to be out of town for a week for work, add in fire tournament and some other misc. delays and I'm probably not going to make my goal of july 3rd. Some progress being made though.

Decided to bore 1/2" holes to get access with a drill bit, they ended up a little oval. I'll have to fix later.

The arsenal including the custom built chisel and drill bit welded to the end of a 1/2" rod.

Custom chisel that breaks the balsa loose between drill holes.

Getting there:

 

[larboc]

I might have found the original problem. I started grinding away the inside of the outer skin and found that when they made the boat, the hull must have hooked inward before they installed the plywood transom core. There was a 16"x3" area where the fiberglass had air between the layers.

This might have contributed to the crack, water, rot.

Ground it all down to solid glass

Braced it out with angle iron, sheetrock screws, then ground off the screws.

Two layers of mat

Followed by a layer of biaxial/mat and strips along the bottoms to back up all the holes in the bottom of the transom from trim tabs, etc. The biaxial/mat stuff that secast sells seems extremely strong compared to the old CSM.

Put all the inner panel pieces back together as much as possible, it's in three main pieces now.

Clamped them to make them flat during curing.

Been hot and dry here, hasn't been fun fiberglassing and the schedule is slipping but making progress non the less!

 

[larboc]

I am wondering what the difference is of going from the outside vs the inside.




I had only seen it done from the inside before this.

If you don't have access to the inside, you can take the outside off but it's generally discouraged. The inner panel is a thinner piece of glass than the outer panel and it's usually put on after the plywood is set in the hull. The outer "panel" is actually the hull, so when you cut it you need to do more work to fix it to make it as strong as it needs to be, plus now you have to make it look good. Nobody will see inside joints so you can concentrate on strength alone.




The glass I'm putting on the core side of the panels isn't really necessary but I figured why not as long as I'm here.

Once the core is poured and cured I'll wrap the I/O hole with biaxial/mat, then I'll tape all the connections between the inner panel and the hull with 3" tape, then cover the entire inner panel with one great big piece of biaxial, 4" past it to the hull at all the joints. Also going to cover the outer skin near the I/O hole in biaxial/mat and then mat then gelcoat.




This will make the inner skin twice as thick, the outer skin twice as thick, and the core twice as thick and from a material 3x stronger than new. I'm shooting for a total 2-1/16" thick transom with no external spacers vs. the original 1-1/8" with plywood spacers.




I am design protecting myself in case the original motor ever goes out, I can build up a 400hp LQ4 without worrying about the transom. Would make for a fun sleeper.

 

[larboc]

Pressing on...




Glassed inner panel back in and all parts back together, glassed in seacast spacers to the new 1.5" center panel thickness and tapered spacers at the outer parts of the transom down to 1/2" to meet the parts I hadn't removed.

Then I ground down the outerpanel and enlarged it by 1/8", and wrapped 1708 out to out through the IO hole. I had ordered no-wax resin through amazon but JD screwed up my order an sent finishing resin instead so I had to use thickened no-wax resin I bought from local shower mfg. It had fumed silica filler in it and really setup hard.

No pics, but I ended up cutting 12"x 1" slots in each of the gunwhale cubbys through to the transom, then glassing in 1708 to make them connect. I then made some funnels to fill into those and spaced the transom out a little there. Made pouring much easier.




Had a pouring party saturday

The transom took 15 gallons, I put the leftover in the floor and floated the old panels back in. Wasn't enough to put the starboard panel in so I've got more stuff ordered and will get than in when it gets here. I didn't take pics, but I also cut the engine bed stringers open and dug out all the old plywood, cut 1.5" OD holes in the bottom of them, then filled with seacast.

Lessons learned:

Seacast looked like it would be too thick to pour into a 1/2" gap but once it starts to slump up it flows very well. Somewhat akin to pouring concrete when you start to screed it. Any little pinhole will leak out goo so have gorilla tape ready to stop leaks. I had used clear packing tape over a couple of bolt holes so I could see when the seacast got to it to make sure it was moving. This proved unnecessary and it melted the tape so I quickly got thicker tape on everything.

I have the back of the boat suspended off the trailer with chain hoists so that the floor evened out for doing the pours. I was surprised that the seacast was actually liquid enough that material was flowing from the high funnel to the low funnel, I couldn't figure out what was going on at first till my old man noted the boat wasn't quite level. I adjusted the chain hoists and sure enough it leveled right out. This makes me quite confident that there are no air pockets left.

You can hit the transom with a ball peen hammer now and it sounds like you're hitting a 2" thick piece of aluminum. Over all I'm happy with the stuff, good to have extra people on hand though. I had two people dedicated solely to tapping on the outer skin with rubber mallets which helps speed up the pouring. It started heating up about 10 mins after we were done pouring and got REALLY hot, parts of it were almost too hot to touch, guessing 120F+. Ambient temps in the mid 70's and everything was in the shade.

I ordered 4 1-gallon pails of Arjay 6011 for doing the rest of the hard to reach floor panels because it's thinner and should do a better job of self leveling through a small hole. And it's cheaper than seacast and faster to get.




I'm not going to make my July 3rd target date, but I'm getting there. I'm HOPING to start getting the engine in next weekend.

 

[larboc]

Not that I need to add any more delays, but I found an entire bravo outdrive setup for $400, fairly local. Tempted...




I'd have to add a seawater pump to the 302, but power steering would be sweet and it would be ready to go should I ever LS swap it.




https://up.craigslist.org/bpo/d/bark...930255293.html

 

[larboc]

I don't remember what outdrive you had on it but I didn't think Bravos were all that desirable

Mine is what I think was called a "1 drive" or some people have called it a pre-alpha. It's basically an alpha. From everything I've read, the Bravo was created because the alpha's weren't lasting behind 454's. I believe Bravo's are superior to the alpha's in most ways. The alpha to bravo swap only requires drilling two additional mounting holes in the transom, and installing a seawater pump on the engine.

 

[larboc]

Man that's a lot of work! Nice job! What do you think you have into it for materials so far?

IDK, I'd rather not total it all up till I'm on the water so it hurts less.




I'm guessing I've spent just shy of $2000 on materials so far for the transom, floor, and engine mount stringers. Also bought a new swim platform and I'll need to buy paint yet.

I'm sure I'll have $2500 into this old boat before it's on the water. Looking forward to having a solid platform to put some more work and money into that actually shows like paint, electronics, fishing gear, etc.




Did a bunch more work on it last night, no pics though.

 

[larboc]

I've long wondered this. Why do they use shitty wood in any portion of an object that is intended to go in the water? Why can't the just use fiberglass or plastic shapes for all that stuff?




Boats are obviously designed to disintegrate as fast as possible so dumb boat people have to buy another.

Balsa or plywood core fiberglass is a really strong, light, conformable, and inexpensive composite so it's an attractive way to make a new boat.

But yea, one leaky screw below the waterline seals the fate of the core. There is now way for it to dry out. Some mfg's are now using composite cores, but not in my price range and it does make for a little heavier boat.

 

[larboc]

Not that I need to add any more delays, but I found an entire bravo outdrive setup for $400, fairly local. Tempted...




I'd have to add a seawater pump to the 302, but power steering would be sweet and it would be ready to go should I ever LS swap it.




https://up.craigslist.org/bpo/d/bark...930255293.html

Umm, I'm looking closer at the pictures and I don't think that's a Bravo, looks like the same drive I have. Any outdrive experts?







Made a lot of progress this weekend, took almost no pics.

I did make a "slab mill" out of a router and some angle iron to flatten out the outer skin. I'm laying layers of 1708 and then milling them off with the router and a 3/4" mortising bit. Then I'm going back and adding more 1708 wherever the router didn't hit. Once it's flat I'll cover the whole area in a layer of mat, sand, then finally PAINT!




Interior is almost done, probably have it wrapped up and bilge painted by wednesday.

 

[larboc]

Its not a Bravo. It says alpha in the title. Looking at the upper its either an early alpha or a 1 drive.

That is most certainly a gen 1 alpha. Could also be a MR but same thing... It should fit your #1 or "pre-alpha" transom mount however I believe the shaft splines are different. Not really that much of an upgrade. If you want a bravo, their abundant down here but not that cheap.

Yea, I texted him asking if he was sure it was a Bravo and he apologized and said he'd change the listing. The ad used to say Bravo.




Hubble, pretty sure all mercruiser splines are the same as are the dimensions and transom patterns, with the exception of the top two added holes for the bravo's. Keep an eye out, I'm not in any rush but if you find a decent deal on a bravo, or whole parts boat, let me know. I'd need everything but the long block. An LS swap would be several years out, but it never hurts to have more crap laying around.

P.S. I'm doing everything I can to have this thing on the water in time for next week's shindig.

 

[larboc]

Built a "thickness" jig for the router, took inner panel down till I had 1-5/8" thickness (into the seacast because I spaced it too thick).

Built back up to 2-1/8" with CSM and 1708.

Filled floors with arjay 6011, taped all joints with two layers of 4" 1708, covered entire floor, stringers, and inner transom panel with a layer of CSM, then painted with two coats of rustoleum gloss white after sanding and an acetone wipe.

Drilled and glassed in stainless drain tubes for the outside bilges to drain into the center, and resined and flared in a new bilge drain tube.







On the water before the snow flew!

I didn't get any pictures of the final assembly due to the urgency. Went from an empty hull to ready to hit the water in about 24 hours wednesday afternoon/thursday with the help of a bunch of drunken degenerates. Got it out for fishing saturday afternoon and found a few dumb lake trout for dinner. All that work, money, and time and the only noticeable difference is that the bilge is bone dry instead of leaking ~1/2 gallon a minuet. O well, I feel better about it anyway!




Now I have to work on the cosmetic repair of the boat, and at some point a repaint of the boat

 

[larboc]

And maybe taking off the winter tarp framework? ��




Sounds like a hell of an upgrade from that sort of leak. Damn

That's actually part of a jumbo planer board setup I rigged up. Eyelets in the tops carry rope to the planer boards. No, it wouldn't have killed me to throw a coat of paint on it. I plan on making one out of some stainless steel conduit, but not this year.

 

[Tech Tim]

Damn you were busting ass on this project. Nice write-up.