1969 Mark Twain 15' Tri-Hull 115 Evinrude - Partial Rebuild

tlzimmerman

Petty Officer 3rd Class
Joined
May 21, 2010
Messages
82
Hello everyone.

Going to try to catalog the rebuild of my 1969 Mark Twain I picked up last week for $300. It has a 1974 115 Evinrude "Starflite"(I hope...pretty sure its a 74...will be asking for help from the community on is one, ezmobee said he could tell the year by pics). First thing I did when I got it home was see if it would run....and surprisingly it fired with little issues after being in storage since 1998. Luckily it was winterized before. I only let it run for about 8-10 seconds with muffs, I was getting no water out of the back anywhere and I didn't want to overheat or score the engine.

I am a somewhat noob when it comes to boat repair, have only ever worked on my dads from time to time when very young, and haven't done that for 10 years since he bought a lund. I am an avid internet and forum user, so I found iboats quickly and man.....so glad I did. I researched for about 4 hours on here before I decided to go ahead and buy the boat. I am somewhat mechanical, and an avid do it yourselfer. This will be mostly my first time working with fiberglass, I do alot of home restoration so I am pretty good with wood. I think its going to be a pretty straightforward process.

I am a little ways into tearing down. All the seats are bad and gone, the floor is rotted in the back, and can't get to the front yet without cutting away part of the cap. The entire rebuild will be done outside, hope to borrow a garage for the glass work though. I am also planning on purchasing a cover once the boat is gutted. The boat will be stored outside during the summer, and hopefully under a lean two in the winter.

This will not be an entire restoration, just building it back to functional. From my preliminary looking, the floor and stringers will be replaced (the stringers are still mostly solid, but are wet in some places...and I am just going to replace them). The transom seems very solid, I can stand on the motor and jump on it with no flex at all, and I tested in a spot and the core is still dry. Lucked out on that. I do not want to split the boat, and the cap in the front comes over to form seats....my plan at this time is to cut out that portion of the cap that forms the seats so I can replace the floor in the front, and mount a swivel seat up front. Seating is up in the air at this point, pondering swivels for fishing because we do alot of fishing.

Was saving and looking for a boat in the $1500 range when we came across this and pulled the trigger. So I am setting the budget at $1500 for a drivable boat with a drivers seat at least (other seats may not fit in that $1500). Boat was $300, so I am looking at $1200 budget to replace floor and stringers, put in carpet, and custom fabricate some storage and new interior trim. Would love a smaller trolling motor in that budget as well, but I think I am dreaming.

Here is pics before starting the initial tear down. I'll post some initial questions for the community after this.

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tlzimmerman

Petty Officer 3rd Class
Joined
May 21, 2010
Messages
82
Re: 1969 Mark Twain 15' Tri-Hull 115 Evinrude - Partial Rebuild

And a couple more...

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tlzimmerman

Petty Officer 3rd Class
Joined
May 21, 2010
Messages
82
Re: 1969 Mark Twain 15' Tri-Hull 115 Evinrude - Partial Rebuild

Couple preliminary questions for the forum. Thanks in advance for any time spent answering.....

1. What year is this engine? I need to order parts for it (waterpump) and I can't find anywhere where it says the year. The previous owners say its either a 72 or a 74......I was told a 72 was an electric shift and this looks like it has cables for the shifting...so is it a 74? I am assuming so but who knows. Any help of a serial number and its location or something I can take pictures of to post for you guys let me know...and I'll get it done.

2. What fuel mix should this run. Once again thought that would be on the engine somewhere but can't find anything. I put 50:1 to fire it up....from what I read the new twcIII or whatever oils you can run 50:1 in these engines, but if thats a bad idea I would love to know. My dad thinks it would be 24:1, or at least thats what his old one was. Any help or advice here would be great.

3. How hard is it to put a waterpump in one of these? Should I order a full kid from iboats, or just the impeller. I probably need a service manual and that would tell me how to do it, what are the best ones out there?

Thats it for now....I'll post more pictures as I continue the teardown. If anyone is in need of original hardware from these let me know...there are parts that won't be reused since I am fixing the boat for use, not a resto.
 

chrismarion

Petty Officer 2nd Class
Joined
Apr 12, 2006
Messages
115
Re: 1969 Mark Twain 15' Tri-Hull 115 Evinrude - Partial Rebuild

To answer your outboard questions with correct answers and knowledge, i would route them to the Evinrude forum. Other than that, most members can help you with anything else. Oh, and have fun while rebuilding. Dont make it a job or you'll hate it.
 

ezmobee

Supreme Mariner
Joined
Mar 26, 2007
Messages
23,767
Re: 1969 Mark Twain 15' Tri-Hull 115 Evinrude - Partial Rebuild

Not electric shift. Good motor. Probably a '74 or thereabouts. I had a '73 85 and ran it for 5 years and sold it running last year. That motor doesn't have a telltale for the cooling system. It may spit some water out of the exhaust relief port on the leg. I'd definitely do an impeller on it given unknown history.
 

tlzimmerman

Petty Officer 3rd Class
Joined
May 21, 2010
Messages
82
Re: 1969 Mark Twain 15' Tri-Hull 115 Evinrude - Partial Rebuild

Hey thanks a bunch.

I posted in the evinrude forum...they seem to think its a 74 as well.

I am going to replace the impeller, not sure if I will do it myself yet or take it to the shop. Never had a lower end off one of these. They don't look too terribly complicated, but the last thing I want to do is get the engine hot.

I am hoping to put alot of cleanup time this weekend in on the boat, of course if my wife goes into labor that will probably put a damper on my plans. She is due june 2nd.

I think the boat is watertight, we got about 2 inches of rain last night and the drain hole plugged with trash.......no cover yet and I had about 6 inches in the bottom this morning. I tilted it up and tried to clear it out. Good thing I am replacing everything LOL.
 

ezmobee

Supreme Mariner
Joined
Mar 26, 2007
Messages
23,767
Re: 1969 Mark Twain 15' Tri-Hull 115 Evinrude - Partial Rebuild

I can actually talk you through the impeller on that motor. That's one thing I CAN do :) As long as you remember to disconnect the shift rod you're good.
 

tlzimmerman

Petty Officer 3rd Class
Joined
May 21, 2010
Messages
82
Re: 1969 Mark Twain 15' Tri-Hull 115 Evinrude - Partial Rebuild

I can actually talk you through the impeller on that motor. That's one thing I CAN do :) As long as you remember to disconnect the shift rod you're good.

Wow that would be greatly appreciated.

What all do I need to order besides the impeller? Is there other seals or anything?

By talk are you saying post in the forum? That would be great, but if I need to call you or something let me know and I'll pm you for a time.

Thanks again
 

ezmobee

Supreme Mariner
Joined
Mar 26, 2007
Messages
23,767
Re: 1969 Mark Twain 15' Tri-Hull 115 Evinrude - Partial Rebuild

You can either buy just the impeller or a complete waterpump kit. The kits gets you the pump housing, gasket and some other stuff. If I were you, I'd take it apart first so you can see what condition everything is in and they order what you need.

The shift rod comes up into the powerhead and connects to a butterfly looking thing underneath the carbs. It's tight but you do not need to take the carbs off to get to it. To drop the lower unit, remove the obvious bolts but don't miss the one that's under the trim tab. The water pump sits right on top of the lower unit. Can't miss it. I'm not that mechanical and was able to tackle the job. Biggest issue I had was forgetting to reinstall the key that holds the impeller to the shaft which I realized just as I had everything reassembled :eek: You can PM me if you need any other help.
 

75TowerOfPower

Petty Officer 1st Class
Joined
Apr 17, 2009
Messages
331
Re: 1969 Mark Twain 15' Tri-Hull 115 Evinrude - Partial Rebuild

Nice mark Twain you have there.

Can you read the Cap. plate? My boat doesn't have one and I am curious as to what it says.

Also mine looked a lot like you before i started working on it. Since its had new stringers, floor, seats, stereo, pin stripes and yadda yadda.

Does your door close? Mine didn't since the floor had fallen so far over the years. I had to raise the front up with a jack then build a structure just to hold the fiberglass walk way up.

Canada06002.jpg
 

tlzimmerman

Petty Officer 3rd Class
Joined
May 21, 2010
Messages
82
Re: 1969 Mark Twain 15' Tri-Hull 115 Evinrude - Partial Rebuild

Yeah I can read it, just barely. Apparently mine was sold without a motor on it, as that part is blank.

Mine states

Model # 15' C3 Tri Hull
Boat # 4609
Motor # blank
Unit # blank
Max HP 110
Capacity 1450 lbs 6p

Yeah my windshield does close, but its all completely loosey goosey, you do have to press out a bit on it to get it to fall into place. That whole front section of fiberglass past the consoles doesn't seem the sturdiest, and I know the floor under it is rotted completely.

I am going to be cutting out the fiberglass front walkway from the top cap so I don't have to split it to replace the front floor, plus I think mounting a swivel seat up there will be better for fishing.....and I might make a couple removable benches or something for when we take it out to ski...I donno we will see what it looks like. I am also planning on putting doors into the front nose area that is hollow.....STORAGE! Once I get it cleaned I am going to post pictures of that to see if anyone has any concerns structurally, but I don't think that front walkway has any structural value to the hull, that should all be in the stringers . Then I am going to fiberglass the consoles directly to the floor instead of having it sit there like the current is, that should make them plenty solid, and I can refit it so the windshield closes good.

I have been told the boat is a 1969...but I don't know where they get that information from (what year is yours?). You are right, they look identical. Did you redo your side pads or were they in good enough shape? All mine are coming out (rotten), and I don't think I am replacing them might just fill the holes...I like the extra room because I plan on installing swivel seats for fishing. I donno have alot more thinking and planning to do first. I am not getting much work done on it at the moment, hopefully this weekend. Wife is 39 weeks pregnant so I get alot of backrub time in right now LOL. Plus I have a bathroom renovation going on inside and part of the deal of jumping on this boat is that I wouldn't forget all my other projects (She is a good bargainer!)
 

75TowerOfPower

Petty Officer 1st Class
Joined
Apr 17, 2009
Messages
331
Re: 1969 Mark Twain 15' Tri-Hull 115 Evinrude - Partial Rebuild

I replced everthing in the boat except for the motor, controls, gages, and steering wheel. So everything else is new. The new floor help stiffen everything and made the boat ride better in the water.

I have back to back seats that lay flat and I have been thinking of doing a captains chair and a bench across the back since my seats suck and nobody wants to ride backwards. I also need some storage in the boat. I was thinking of converting on of the under the front seats into a built in cooler but have tried it out yet.
 

boatflipper

Chief Petty Officer
Joined
Jun 16, 2009
Messages
500
Re: 1969 Mark Twain 15' Tri-Hull 115 Evinrude - Partial Rebuild

Lookin good for sure!! I do believe we have the same model boats...
My front floor that is built into the cap was flexing bad too so I also built a structure under it for support, but I think I recall you saying you are going to cut that out...
Im glad I saw the interior panel pics because I didn't have the doghouse and now I think I can come up with one.
Good luck on the build and keep the pics comin!
 

tlzimmerman

Petty Officer 3rd Class
Joined
May 21, 2010
Messages
82
Re: 1969 Mark Twain 15' Tri-Hull 115 Evinrude - Partial Rebuild

Alright, got her gutted and am started on the grinding.

Man cleaning her out was a pain. In the back there was places with 3 inches of dirt/rotted wood. All the stringers are out, I have it ground all the way around the edge, or very close to. Checking the transom...ironically there is no rot at all, some places were the fiberglass needs replaced but the wood under it is in great shape...so I really lucked out there, going to put a little fiberglass over the bottom parts of it to make sure its watertight, but thats it for the transom.

I went ahead and cut out the front seats, I am just going to put a deck up there with storage under it, and then make some cushions I can set on the floor so people can just sit flat on the flat front deck for play, or my swivel seat will go up there for fishing. The plan now is to put the floor in just how it was, then build 2 deck supports onto that and then put in another deck even with where I cut out the old from the cap. Should work rather nicely I think, might be a little high but I also plan to do some bowfishing and the deck will be nice for that as well, plus I am going to have plenty of storage under that top deck, which will be nice.

Had my first kid on the 6th, so really haven't gotten much time to work on it, but man having the right tools helps. For cutting out the stringers and everything I used a diamond blade for concrete on my 4.5 inch grinder, then for grinding I am using a flapper disk...and they are both working amazing. $15 in blades made things go so much faster. The whole outside took me about an hour to grind down flush with the flapper disk, I am going to go in and cut the stringers closer to the deck now that I have more room to work with the bulk out before I grind them down as well.

Got a water pump impeller and a service manual ordered, plan on doing a carb kit as well but the engine does fire and run....very happy with that.

I am a little upset with my local stores...been trying to find unwaxed resin ANYWHERE and someplace that has rolls of fiberglass csm or cloth...nothing but small kits and gallons of waxed resin. Oh well, I guess I will be making a big order from UScomposites and paying the crazy shipping.

Here are the new pics.
 

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tlzimmerman

Petty Officer 3rd Class
Joined
May 21, 2010
Messages
82
Re: 1969 Mark Twain 15' Tri-Hull 115 Evinrude - Partial Rebuild

Hey quick question that I forgot to ask...does anyone know if they make a replacement rubber fitting/gasket that holds the glass in the aluminum windshield? Would love to find some because mine on this boat are in really bad shape.
 

75TowerOfPower

Petty Officer 1st Class
Joined
Apr 17, 2009
Messages
331
Re: 1969 Mark Twain 15' Tri-Hull 115 Evinrude - Partial Rebuild

I am not to sure if you need to buy the exact part. You happen to know a guy who does glass for cars?

As for your question about the side panels, mine were removed a long time ago. I would love to have them since you can store a lot in those things. I have trouble putting all the life jackets, toys, and safety stuff on the boat. I might cut out the front seat ares to use them for storage.
 

tlzimmerman

Petty Officer 3rd Class
Joined
May 21, 2010
Messages
82
Re: 1969 Mark Twain 15' Tri-Hull 115 Evinrude - Partial Rebuild

I am not to sure if you need to buy the exact part. You happen to know a guy who does glass for cars?

As for your question about the side panels, mine were removed a long time ago. I would love to have them since you can store a lot in those things. I have trouble putting all the life jackets, toys, and safety stuff on the boat. I might cut out the front seat ares to use them for storage.

Yeah my bro works at a body shop....they look different than the ones for windshields...wonder if they are the same as the ones in like side windows...I'll have to have him look at em.

I thought about the storage too..the good thing is if I decide to put them in later...its an easy add. I am leaving them off for now. I think I will have a good portion of storage under my front deck, I plan on putting a good size hatch and leaving access from under both consoles and the front step. Lotta room up there. And I plan on having storage next to the bilge in the back as well.
 

tlzimmerman

Petty Officer 3rd Class
Joined
May 21, 2010
Messages
82
Re: 1969 Mark Twain 15' Tri-Hull 115 Evinrude - Partial Rebuild

Digging this out of the depths. Well of course, life happend once we had our baby girl, and this project got tarped and put away for awhile. But...its TAX REFUND TIME, and we are both really looking forward to getting on the lake this summer, so its time to drag it back out.

I have been getting an order lined up, and after reading and rereading (since I have been away from the forums for awhile) the fiberglassing posts, I wanted to post my plan for fiberglassing of the stringers and deck, and the amounts I plan on ordering, and hoping the experts will tell me if that is sufficient.

Stringers will be 1 layer 1.5 oz csm, followed by 2 layers of 1708 biax with the edges taped with 6oz cloth in between.

Bottom of deck will be 2 layers of 1.5 oz csm for waterproofing. Top of deck will be 1 layer of 1.5oz CSM followed by 2 layers of 1708, taped in between layers on edges with same tape.

I am a complete rookie with fiberglassing, and I have read all I can. Can someone tell me if thats over/underkill for the stringers and deck on this build? Stringers will be outdoor grade plywood, as will the deck.

Plan on ordering.....

30 yards of 50" 1.5 oz csm
15-20 yards 50" of 1708 biax
6 gallons of 4.35 resin
50 yard roll of 8" cloth tape
2lb tub of 1/4 cs fibers
5 quarts of aerosil-cabosil

Fibers and cabosil will be for pb type stuff to fill the edges of the deck.

Am I anywhere close? Any advice would be appreciated.
 

tsnipes

Seaman
Joined
Jul 12, 2010
Messages
66
Re: 1969 Mark Twain 15' Tri-Hull 115 Evinrude - Partial Rebuild

Hey, tlz. Congrats on the new daughter. Enjoy her, she will be grown before you know it. I don't really have much advice on you supply order, but I am in about the same boat as you. No pun intended. I have an 18' Thompson that mt father-in-law gave me last year that is in need of a transom replacement. I am looking for the same type of advice as you. I am anxious to begin working on it now that the water is warming up. I will be following your build and hope to be posting my own soon. I would love to take mine out this summer and hope that you are able to as well.
 
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