1977 Mako 23 Rebuild

[Scottb22713]

Hi everybody my name is Scott and I recently purchased a 1977 Mako 23. I bought it knowing that there's a good chance I will have to rebuild the boat. Well sure enough after inspecting the transom there was a lot of wet and rotten wood in there so it's time to rebuild. I've decided that while I'm already having to rebuild the transom I might as well close the transom and add a bracket. I have done a ton of research the past couple of weeks and this forum has been a huge help. The point of this thread is so I can ask questions along the way and that somebody else in the future has another thread to learn off of. I know this project is going to be a lot of work and I'm excited about it. I've already begun the transom tear down and here arises my first question. I pulled two 3/4" pieces of plywood out of the transom equaling 1.5 inches. I will be putting a 300hp 4 stroke on an Armstrong bracket on this boat. I was thinking I could increase the size of the transom by using three 3/4" plywood panels equaling 2.25 inches. I will be using epoxy resin with chopped mat fiberglass in between each panel and encapsulating it all with many layers of 1708. Does this sound suitable to handle the extra weight and setback from a heavy 4 stroke on a bracket?

[wolfie]

sounds like a worthy project. All the info you need is here if you take the time to find it.

and I'll be the first to say - PICTURES! []

[Scottb22713]

Came with a 150. Definitely under powered but it works and I will be selling it





So far so good on the outboard stand I built





This gas tank is only 46 gallons. No thanks. I'll be replacing this



Finally got the inner skin removed. Time to get rid off all the wood, clean it up and put in the new material



I bought the boat less than 2 weeks ago. It's been raining in Florida for a few weeks now but I've been able to get on it a few times here and there. Finally I had a couple days with little rain in the forecast to get a lot knocked out. I'm excited to get this transom rebuild and makeover done.

[Sharpest]

You sure about that tank capacity? My 76 23 had a 76 gallon tank iirc. Replcing it with a ~90 gallon unit from Sunshine.

[Scottb22713]

No I'm not sure about the capacity. That's what I was told by the seller but I haven't confirmed it. 76 gallons is much better but I'm more interested in the 90 gallon tank you mentioned. I'll have to take a look

[Woodhunter]

My 1977 21 foot Mako has a 85 gallon tank.

[Scottb22713]

If my tank is 46 gallons it's definitely not original. I still haven't pulled it. The little time between work and rain I've been working on this transom but pulling the tank is next on the list. I'm having a hard time deciding how much capacity I need. I never want to wish I put a larger tank in

[Scottb22713]

I would really like to hear your opinions on whether I should just stick with 2 sheets of 3/4 plywood or upgrade to 3 sheets of 3/4" plywood for the transom core. Is the extra thickness worth the extra weight? Is it necessary for a 300hp 4 stroke on an Armstrong bracket? I would love to be able to save some weight back there but I don't want to sacrifice strength.

[Slack Tide]

I dont think I've seen anyone do 3 layers in their transom. I'm no pro but Im pretty sure youre going to get your strength from your glass layup. If anything I would go beefier on the glass to achieve some increased thickness. Although this will be slightly more costly since if you double your layup, you'll use twice as much epoxy. Unless someone else can chime in with their thoughts, this is just my .02

[thejeepguy87]

I agree that 3 layers is not needed. Use extra glass. The core is basically for compression loads. The glass layup is what transfers and spreads the load out to the hull.

I have two 3/4" sheets of kay-cel, or coosa board, and many layers of glass inside and out. I hung a bracket and twin 225s a year ago and do not have the slightest bit of cracking or issues and I run over curbs more frequently than I should admit. Even with that stress it is fine.

[Scottb22713]

Thanks guys I think I'm going to use two pieces then. It makes sense that the glass is what really takes on most of the pressure and the plywood is mostly there for compression and structure. I'll go heavy on the glass instead.

[Scottb22713]

I got the rest of the old wood out and it was much harder than expected. The wood had an extremely solid bond to the fiberglass still. It's a shame the previous owners didn't do a better job at sealing off their holes.



Spent some time on the grinder. I had to cut the grinding time short because I had somewhere to be. A little more grinding and sanding and I'm ready to start the rebuild process.

[Scottb22713]

I got my outboard bracket today. I'm nowhere near ready to install it but I got a great deal on it so for now it will sit in the garage. It's not sitting on that rock by the way, the rock is there to keep the dolly from moving

[Scottb22713]

The amount of grinding and sanding I've done is incredible. I have to admit I had no idea this would be as time consuming as it's turning out to be. That doesn't change anything though. I'm 100% committed to finishing this project and getting on the water. This hole was from me grinding to the bottom of a stress crack. It's patched up now



I decided to get a cheap sheet of Styrofoam insulation to create a template for the transom core. It worked pretty good and I can now start forming the core.



Right now I'm hanging onto every inch of hope that I will not have to redo all the stringers in the boat. I have only inspected the stringers where I made the cut to redo the transom but there is absolutely zero rot in that section. The wood did have quite a bit of moisture in it though. Only time will tell but for now I'm remaining optimistic about it

[Scottb22713]

Using the foam as a template worked out okay. I made the cut a hair too big so I can fine tune it with a sander. Here is the core fitted into the transom.



After getting both 3/4" pieces cut out and tested, I coated the wood with 3 layers of epoxy resin and allowed the wood to soak it in.



Once the wood stopped soaking up the resin I mixed a putty using epoxy resin, Cabosil and 1/4" chopped strand. I sandwiched the pieces together and put weight onto the board to let it cure.



I wasn't sure how much weight to put on the board. I've heard you want a good amount of weight distributed evenly on the board but also not too much that all the thickened resin seeps out of the edges. I literally just finished this so there's still time for me to add or remove weight. I would appreciate any input on the weight distribution. There is currently about 400 pounds on the board.