1978 MonArk SuperSport Restoration

jrodp

Cadet
Joined
Aug 19, 2021
Messages
9
I was recently "gifted" a 1978 MonArk SuperSport IV boat and 70 horse Johnson motor, which was in pretty good shape except for a rotted spot in the floor where a stool was bolted down. I have never owned a boat so I began to do some research on how to fix it, and came across this site. Long story short, you all know what I'm now dealing with, and old boat full of water, soaked foam and some rotted wood.

So, after cutting out the floor this weekend, we found it was mostly wet throughout and completely rotted around where the stool was. I am unsure of the transom, it feels solid and a boat repair shop said it looked good, but from what I have read here, it is probably bad also. Thoughts on that?

I found this boat does not have wood stringers but instead 4 foam-filled fiberglass stringers that run the length of the boat. I found a post on here with a similar boat and stringer design. In reading that post, it seems I should probably cut the tops off the stringers and pull out the soaked foam. I cut out a small section of one of the stringers where the rotted seat was bolted to see what was inside. My question is, should I cut the entire length of the stringer top, or just enough to get the foam out? I figure I could save some fiberglass work by only cutting out small sections.

Another question I have, when cutting out the floor, I left about 4 inches or so around the edges to tie the new floor to (I saw that on a video somewhere). So should I cut all of that out back as close to the wall/hull or leave the 4 inches?

I have many more questions, but I will start with those. I will also attach some pictures.
 

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jrodp

Cadet
Joined
Aug 19, 2021
Messages
9
I was recently "gifted" a 1978 MonArk SuperSport IV boat and 70 horse Johnson motor, which was in pretty good shape except for a rotted spot in the floor where a stool was bolted down. I have never owned a boat so I began to do some research on how to fix it, and came across this site. Long story short, you all know what I'm now dealing with, and old boat full of water, soaked foam and some rotted wood.

So, after cutting out the floor this weekend, we found it was mostly wet throughout and completely rotted around where the stool was. I am unsure of the transom, it feels solid and a boat repair shop said it looked good, but from what I have read here, it is probably bad also. Thoughts on that?

I found this boat does not have wood stringers but instead 4 foam-filled fiberglass stringers that run the length of the boat. I found a post on here with a similar boat and stringer design. In reading that post, it seems I should probably cut the tops off the stringers and pull out the soaked foam. I cut out a small section of one of the stringers where the rotted seat was bolted to see what was inside. My question is, should I cut the entire length of the stringer top, or just enough to get the foam out? I figure I could save some fiberglass work by only cutting out small sections.

Another question I have, when cutting out the floor, I left about 4 inches or so around the edges to tie the new floor to (I saw that on a video somewhere). So should I cut all of that out back as close to the wall/hull or leave the 4 inches?

I have many more questions, but I will start with those. I will also attach some pictures.
If I decap the stringers, should I save the pieces and use them to fill back in a glass/tab over them?
 

GSPLures

Chief Petty Officer
Joined
Sep 3, 2019
Messages
564
Its best to cut the entire deck out and go with all new wood. Not much more work and zero chance of leaving something wet/rotted.

For the transom only way is to do core samples along the bottom and see (inside and dont go all the way through). If good patch the holes, if not you have to replace.

My boat had wood/fiberglass stringers, your glass is structural and the foam was a form. I will let someone else with better knowledge of those type of stringers answer the best way to deal with those.
 

jrodp

Cadet
Joined
Aug 19, 2021
Messages
9
I am working on cutting out the remaining deck but still curious about the stringers. Anyone have any advice on the best way to remove the old foam and repair those?
 
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