Mark twain tri hull advice

[brwneyedsue]

We purchased an old 70's Mark Twain trihull boat a couple years ago. We had issues with the motor and ended up buying a $1400 motor from a used boat dealer a few weeks ago. The floor was squishy so we decided to replace it (after purchasing the newer motor). We would love to get a couple years worth of enjoyment out of this boat instead of just dumping it and selling the motor for a loss. We are not experienced with any type of boat repair and have opened a can of worms that we don't think we can deal with. I have some VERY novice questions. First....can we replace the stringers with composite wood (decking?) to keep from having to use fiberglass/wood? What would happen if we used composite decking for stringers and floor and put the epoxy foam under it for flotation and then call it good? I know....not ideal, but would it work? I've watched a few repair videos and am in tears thinking of how much time and money and expertise this might take. We don't want to sink thousands into this boat, nor do we want to literally SINK! We'd just love a couple years of getting it on the water and then hauling it to the dump. Thanks for your time and advice.

 

[bansil]

I did this years ago, i do not recommend it, it worked and i got 3 years out of it and sold it, i told the guy what i did before purchase.

3/4 EXTERIOR plywood ( it has waterproof glue) i cut the pcs out and notched them like the card board dividers in. Case of wine.

several coats of varnish on all sides/edges

when i installed the floor grid, i glued bottom and all joints with a construction adhesive , then installed plywood on that grid for level floor, stored in barn and i got my use out of it.

my hull was in great shape Nd this was years before finding out about youtube and forums, good luck be safe and enjoy

that composite board might be good if it can be screwed and glued

again my disclaimer is do not do what i did, it worked but is not proper way to replace stringers and floor

 

[jbcurt00]

1500-2000 is a low rehab cost if you do all the work yourself, and dont waste materials, time or money doing it for the 1st time. Many (most? some?) spend more.

there arent any short cuts do doing it right.

done poorly or wrong, its a danger to those in your boat and those around you when its in use. No way to know if this is the last trip out or when something bad will happen

every boat, boat rehab and boating conditions are different, what might have worked for 1 might not work for another when you take short cuts.

done porrly puts your $1400 motor at risk too

do it correctly or dont do it, the stakes are high, even in flat, slack, protected or calm water

DIY helpful info:
http://forums.iboats.com/forum/boat-...80#post5550980

theres lots of stinky, nasty, hard work ahead, but if you choose to do it, the resto forum will be here to help guide you

Spending 2K on this boat, when rehab'd correctly, will give you a nearly new boat, for significantly less then a new boat, and a nearly perfect boat thats significantly better built (condition) then 99.99% of the boats available for 5K or less in most places.....


where are you located?

a $1400 motor would also be right at home on an appropriately sized tinny. Aluminum boats need rehab too, but are often less difficult to complete and some consider them easier in general for 1st time rehabs.


no. Skip the composite fake wood

 

[briangcc]

Not to be the bearer of bad news but if your floor and stringers are shot, I would wager the transom is in need of attention as well. Addressing only the floor and stringers would leave you open to catastrophic failure - ie. motor falling off the back of the boat. Should you wish to avoid using wood, there are pourable products such as SeaCast which could used instead. They are pricey but won't rot down the road. A few restores have been completed using these products.

Most people who come here looking for advice have no previous experience completing a repair such as this. There are some who throw in the towel but those that complete the work have learned new skills and can now handle most repairs on their boat. They're also very comfortable with the knowledge that the next wave they take isn't going to shake something vitally important loose.

You could sell the boat and motor at a loss and the next purchase could be hiding even more issues.

It's your call as to how you proceed. Should you choose to restore it correctly, the members here are more than willing to lend expertise and some cheer leading when you need it.



For me: It'd become a family project that my boys could use once they are of age and have taken their boater safety class.

 

[Lightwin 3]

In any case, the stringers need to be bonded to the hull. You have to research what, if any, products can accomplish that with composits.

There is nothing wrong with wood as long as it is installed correctly and completely encapsulated.

 

[444]

Your floors are shot. Your stringers are shot. Your transom will be shot as well. To change the transom you will need to separate the upper hull off the lower hull. IMO, keep your motor and trailer and haul the hull to the dump. You know those jokes guys make about BOAT standing for Break Out Another Thousand or a hole in the water you throw money into? This is the boat they're talking about. You would be time and money ahead looking for an aluminum hull you can buy and use your motor and trailer with. They can be found for significantly less than what you will spend on lumber, fiberglass and resin, not to mention your time.

If you decide to repair, your new stringers need to be real wood and bonded to the hull with fiberglass for the full length. This is what gives the hull its strength and the fiberglass and resin is what seals the wood from moisture. The stringers need to be fiberglassed to the transom as the transom and stringers act as a lever to lift the hull when you nail the throttle. For the stringers I would use fir if you can get it, if not spruce or pine or doubled up 3/4 exterior grade plywood bonded together. All the wood should be sealed up with fiberglass and resin.

The flotation foam in there will need to be replaced. It's going to be all old and water logged doing more harm than good. The foam only serves to keep your boat from sinking to the bottom of the lake if there's a water leak. It has nothing to do with normal boat operation.

Not to be the bearer of bad news but if your floor and stringers are shot, I would wager the transom is in need of attention as well. Addressing only the floor and stringers would leave you open to catastrophic failure - ie. motor falling off the back of the boat.

In the case of my in-laws, they bought a cheap boat without bothering to ask the opinion of the only guy in the family who's done any boat work (me). After I told them the transom was soft and needed to be replaced they said they'd just brace it with some plywood, which they never did either. On the maiden voyage the 50hp outboard ended up on the bottom of the river and the hull ended up 3/4 submerged before they swam to shore with a rope to pull it out. Fortunately for them it was a small, shallow river.

 

[southkogs]

70s Mark Twain would be in the 16' to 18' range, right? Outboard?

I would suggest finding another hull out on craigslist. You'll be one of the fortunate buyers who doesn't have to worry about what kind of shape the engine is in. And it should be cheaper than rehabbing the Mark Twain.

If you're really hooked on the Twain, they're cool boats. Nothing wrong with doing a real live rebuild on one. But it's gonna' be hard and expensive.