My first boat needs help.

Let me start by thanking you guys for such a great site with so many great topics. Ive been around boats a fair bit and have always been the passenger. I did a job that the guy couldnt pay for in the end so he offered up a 1980 Renken 157 Bow Rider with a Mercury 80EL. The motor runs strong and always fires right up.
I knew the deck needed work and assumed the stringers were bad as well given its age. Turns out, the stringers were replaced before by some one as well as the deck obviously. I only found 3 stringers in the boat that were poorly placed and glassed in. They were never bedded or tabbed. and I could literally grab the glass and pull it out. The transom is also bad. Im kind of eager to get going on this as there is still time here in Ohio to get back in the water.
Here are my questions I hope some one can help me with.
How many stringers should be there? Should it be cross sectioned (boxed in a few sections? How do I separate the cap from the hull to replace the transom? Can I use 1700 Biaxial cloth for all of this or should I use 1708 Biaxial mat? Epoxy or polyester?
Here are some pics of the boat although not really helpful, and a quick and dirty plan for my replacement stringers and deck. Im heading up tomorrow to get some better measurements and finish ripping the floor out and try to map where the stringers are/were.

 

Welcome to the forum.

Pressure treated lumber isn't the way to go, with polyester or epoxy and CPES is useless without an overcoat of 10 mils of regular epoxy, so it's a dubious application at best. You can use conventional polyester or vinyl techniques, bedding, tabbing as the origional was or epoxy. The choice of 1708 will be fine with the styrene based goo's but regular biax is all that's necessary with epoxy.

Most of the problems with these older builds is the lack of weep holes and poor workmanship in tabbing and sealing things under the sole. Your advantage is you can afford the time to do it right or at least far better than they did previously. Use regular lumber, such as Douglas fir or SYP, as treated stock doesn't let the goo's soak in like the old CCA pressure treated products did.

 

Thanks for your info PAR.
Im wondering about my drawing as well. Do you think this is the right way for me to approach this project? Im comfortable with laying glass and tabbing and the bedding doesnt scare me too much. I just want to make sure im going about it the right way. Ive read alot and watched a ton of videos but I just want to be sure I have enough support for the deck which will be 1/2" Ply. Ill also be doing new flotation foam towards the end when i can build up the boxes for it. Do you think it would be ok to add foam to the outer most sections of the stringers?

I hate to be a bother but when in doubt, ask a bunch of questions of people that know their stuff.

 

Your stringer and partition arrangement looks fine. You can foam if you like though it's not really necessary. The sealed compartments will act the same way without the foam. Personally, I like to let the moisture out, not trap it with foam filled compartments.

 

Thanks again PAR. I know it had foam from the get go and maybe Ill just add it back in where it was when i began to dig into it but try to seal the wood away from the foam. The foam I removed was along both sides beneath a shelf type of arrangement about 6-8" above the deck. If that makes any sense.
I know Renken boats arent very popular and they (general comments found in other sites) may be correct in saying that they weren't very well built but its my boat and I like it. Besides, its really just cost me the materials Ive invested into the job to begin with (300) and what ever it costs me to fix her up. I havnt found an 80HP outboard for that price.

BTW, what would be best to glue my transom up with? I know its 2 layers of ply, I have not measured the thickness but I believe its 1 1/2" so i need to laminate two sheets together and glue it to the transom outer skin and lay up new glass on the interior.

 

I recommend epoxy for novice laminators, simply because it's easier to get right and stronger. The amount of tabbing will be the big difference. The factory used enough to get them though their price point and warranty. You can add more here and there, greatly improving its strength and durability. Your transom core will be two layers of 3/4" plywood, glued together and tabbed to the hull shell. I prefer to use 3 layers of 1/2" plywood, particularly if it's big box store stuff and a 2" transom (4 layers of 1/2") isn't a bad idea on bigger HP outboards.

Actually, the location of the foam makes perfect sense, if you look at the boat when it's swamped with water. If it's all under the sole, the boat will want to flip over, which tends to spill the beer cooler (not good), so to keep the boat upright yet swamped, the floatation is best on the hull sides and under the side decks.