Best way to replace deck on 1975 Mako 20'

[jwidgeon]

The deck on my boat (1975) has several soft spots and spider cracks and needs to be replaced. I'm putting a new fuel tank in so I figure I might as well work this in to the project while I'm at it. There are some areas where the deck almost feels swollen, making me think there is some serious waterlogging in the foam/wood

I've read several different ways to "skin the cat". Which is best? Feel free to give other suggestions.
1. Cut the deck, leaving a 3" lip around the edge. Use the lip to attach a 5" shelf to the bottom of the lip, to give the new marine plywood something to sit on.
2. Cut the deck entirely, right up to the edge.
3. Cut the top layer of the deck out and remove the old core, leaving in the bottom layer to put the new plywood on. (This is one that sounds easiest, but I won't do since I need access under the boat to replace foam and check the stringers.)

The livewell compartments (one bow, two stern) are in decent shape, do I just cut around them and keep them in/bond them to the new deck?

Once the old deck is out, foam replaced, etc, I'd do the following:
1. Cut 3/4" marine grade plywood to size and coat both sides in resin. Fix to deck.
2. Fiberglass new deck. Then primer and finish (Thoughts on Interlux Perfection over Epoxy PrimeKote?)
3. Non-skid

As you can see from the pics, it doesn't LOOK bad, but walking on it you really feel it.

[Sir Mako]

I'm surprised no suggestions. I have a 76 myself with the same deck layout. I have a couple of soft spots myself. My problem is this would be my first time doing fiberglass work so i was looking here for suggestions you may get. Your floor a lot better than mine to be honest. I was already planing on doing another color for the floor since the current color get extremely hot during the summertime. If you do your floor, please post your progress. It would help me to see what I have forward to look for. Sorry I can't be any help for you on this. Thanks

[jwidgeon]

I'm surprised no suggestions. I have a 76 myself with the same deck layout. I have a couple of soft spots myself. My problem is this would be my first time doing fiberglass work so i was looking here for suggestions you may get. Your floor a lot better than mine to be honest. I was already planing on doing another color for the floor since the current color get extremely hot during the summertime. If you do your floor, please post your progress. It would help me to see what I have forward to look for. Sorry I can't be any help for you on this. Thanks

Thanks for the comment! It's my first time messing with fiberglass too, so I'm a little nervous.

[mrdelgado]

I'm in favor of the 3rd option, which you don't want to do. Are you assuming the foam is saturated and stringers are compromised? That's a lot of extra materials/ labor/$$ if you don't know for sure.

[jwidgeon]

I'm in favor of the 3rd option, which you don't want to do. Are you assuming the foam is saturated and stringers are compromised? That's a lot of extra materials/ labor/$$ if you don't know for sure.

I'm not sure, but the bow area is rather "swollen". Could easily be the wood deck that's saturated, but I'm curious if there is something underneath. Maybe I should just roll with option 3 and see how it is once I pull it up.

[mrdelgado]

What I did to my 25. I cut the top skin off and tried to preserve it for reuse. Then removed the wet core. it was so wet, it peeled right out. If you're concerned about wet foam, cut a few foot diameter holes in the bottom skin and pull some foam to inspect. Easier to patch a few small holes for inspection, rather than the whole deck. Keep the glass you cut out and reuse. This way you'll get your piece of mind and not waste time and money.
A lot of 20's were cut open on here for your reference for where to inspect.

[jwidgeon]

What I did to my 25. I cut the top skin off and tried to preserve it for reuse. Then removed the wet core. it was so wet, it peeled right out. If you're concerned about wet foam, cut a few foot diameter holes in the bottom skin and pull some foam to inspect. Easier to patch a few small holes for inspection, rather than the whole deck. Keep the glass you cut out and reuse. This way you'll get your piece of mind and not waste time and money.
A lot of 20's were cut open on here for your reference for where to inspect.

I'll give this a shot. Thanks for the feedback!

[mrdelgado]

No prob, take a look at what i did on page 57. Worse case, your inspection is bad, you find really wet foam and delaminated stringers and you have to cut the whole floor up. But highly doubtful, unless your water line is under water from excessive water weight and signs of cracking on the chines from bad stringers.

https://forum.classicmako.com/forum/...d-floor/page57

[jwidgeon]

No prob, take a look at what i did on page 57. Worse case, your inspection is bad, you find really wet foam and delaminated stringers and you have to cut the whole floor up. But highly doubtful, unless your water line is under water from excessive water weight and signs of cracking on the chines from bad stringers.

https://forum.classicmako.com/forum/...d-floor/page57

Wow, looks great! Did you have any trouble faring and sanding the top skin back to the deck? That's what is the most intimidating to me, since I have no previous experience working with fiberglass.

Easy enough to cut the top skin off and replace the core, I'm just worried that I'll be able to evidently see where I cut.

[mrdelgado]

Fairing wasn't bad. The key is to test fit everything before you start mixing resins. I pulled out 1" core, but went back with 3/4" foam. I knew I'd need wiggle room since I'd be troweling in coreing compound. It was similar to tiling, buttering up the core and laying in. You'd rather be too low, than too high and be adding filler. Last thing you want to do is be grind high spots. Once the core and top skin is in, start filling the seam using a 4" spreader, sand then skim coat with a 6", then 8 ". Key is to do multiple coats, applying parallel with the seam and perpendicular.

[Sir Mako]

Definitely post some pictures of your progress. I would like to see it and maybe give me some ideas. I will ( If ok) post a few pictures of my deck here to see what you think? My soft spots are not real bad but stepping on them, it's clear it's on it way to getting bad. Mostly from cracks in the floor. Most of the foam seems to be gone from the console back. I'm pretty sure what's up front is wet. I just know removing and labeling the wires alone is going to be a task and disconnecting just to remove the center console to check the tank out. I thought about a snake cam but everything been on so long, that I am afraid what will break just to take a look. lol. Hope yours is in better shape. It looks good though. Good luck with your boat.

[jwidgeon]

Definitely post some pictures of your progress. I would like to see it and maybe give me some ideas. I will ( If ok) post a few pictures of my deck here to see what you think? My soft spots are not real bad but stepping on them, it's clear it's on it way to getting bad. Mostly from cracks in the floor. Most of the foam seems to be gone from the console back. I'm pretty sure what's up front is wet. I just know removing and labeling the wires alone is going to be a task and disconnecting just to remove the center console to check the tank out. I thought about a snake cam but everything been on so long, that I am afraid what will break just to take a look. lol. Hope yours is in better shape. It looks good though. Good luck with your boat.

Feel free to post pics! This forum is all about helping one another. I was intimidated by tackling the rat's nest of wires that was in my console when I got it, but once I started pulling wires and replacing, it quickly all made sense. I'm going to move the batteries from the stern to the console while I do this, so it'll make it worth my while.

[Sir Mako]

Feel free to post pics! This forum is all about helping one another. I was intimidated by tackling the rat's nest of wires that was in my console when I got it, but once I started pulling wires and replacing, it quickly all made sense. I'm going to move the batteries from the stern to the console while I do this, so it'll make it worth my while.

I agree it's a rats nest in the console. lol I'm also looking into moving my batteries there. I bought a bunch is new switches to replace the old fuse pull type. Mine is still mostly original nothing has been upgraded on her. Took a lot of the teak off and over time some of it has been misplaced so I may be looking into something else to replace it, Hatches and such. It's time to give her a good paint job inside and out and some upgrades.

[Sir Mako]

I was on it yesterday going through some of the wiring to clean it up to get the motor started ( Ignition panel) the switch itself pretty much is gone so going to get a new one today. I did notice having the cover off the battery area I could hear air when I walked on a spot next to the live well. It doesn't feel real soft but obliviously that's not a good sound. Once I get some pictures done. It will give you a better idea of what I am up against. I didn't see any cracks in your floor but mine has some. My tank is questionable since I really don't know the history of this boat other then the haul once was starting to de laminate and was repaired. I have had the boat around 10 years with not any issues. I have filled the tank in the past and never smelled any fuel in the haul or seen any. It has sat for some time now but with pretty much the tank being empty. I would like to get one of those snake camera but not sure how to get into it since the gauge part looks like if you try and remove it, it most likely would break. We pretty much have the same boat/ haul set up so we could bounce some ideas of some fixes and improvements. I will try to get some pictures today while I am out there. My plate is pretty full with working around my place. lol. I'm also working on my truck since it will be pulling this boat.

[Sir Mako]

Well I did get some pictures taken of my 76. Please excuse how nasty it is. Wife was sick for a few years and I hardly had anytime for anything other then taking care of her full time. Anyway, You can't really see the cracks in the floor to well or any but here is what she looks like. I'm looking at over six months of work ahead of me bring her back to here glory.