1987 170 Rebuild

[AquasportEd]

Hello All!
I mentioned in the introduce yourself thread that I was the new proud owner of 1987 170. Boat is currently in my yard on a trailer and has no outboard. Ill include several pics shortly, but the game plan is basically a total overhaul. The deck feels soft in some areas, hull needs a repaint, tank was completely shot, and though the transom isn't visibly damaged, it appears someone has attempted a repair to it at some point in time.

I hope to start cutting her up soon, so I'm looking for some advice. My current idea is assess the transom first. I think more or less regardless of what I find I should remove it, and build it back up. The thought here being the boat will be getting new stringers (almost certainly soaked), and a new deck (hoping to go honeycomb). And if I'm getting that deep into it, the transom should be of a known quality too.

After replacing the transom, I plan to remove most of the deck, as well as the liner. At that point, remove any saturated foam, grid like hell, and refoam the stringers, possibly raising the floor an inch in the process (would like to be self bailing).

Based upon the above information, does it sound like a viable plan? And any comments on how to tackle the transom rebuild? Thinking of tackling it from the outside skin, what would be the best tool to begin peeling back the skin to remove the wood core?

I have zero glass experience, so this will definitely be learning experience. A few years ago I rehabbed an aluminum boat from the ground up, so I have some idea of how a project like this may go. 

[AquasportEd]

[RickK]

Your plan seems fine. The transom looks kinda lumpy from the outside. I'm not sure why though unless you have some glass delamination.
What is your plan for new power? The 170 is usually sensitive to added weight in the aft but based on your demo/rebuild plan you should be able to compensate for extra weight and offset. Cutting in from the outside can be done but it is a lot more work, but if the glass is delaminating on the outside, it'll have to be cut out anyway. I hate to say but I might take a 80 grit grinder to some of the spots and see what they look like below the gelcoat.
Is there soft spots in the floor?  Usually in the aft behind the tank well there is but that is because there is no support between the stringers there.
One thing you can do before taking the big cutting plunge on the floor is take a drill with 1" hole saw and drill a hole about a 1/2" above the place where the stringer meets the bottom and as far aft as you can. See what comes out of it and you can also stick your finger in and see if it is damp.  Look at the drainage initially and then raise the front of the boat for a few days and see if it increases. Most of the time the farther forward you go in the stringer the drier they are. Also usually only the lower couple inches are wet/saturated.

[AquasportEd]

Rickk,

The transom does appear wavy, as though someone was in there before and didnt sand or prep it well. It doesnt seem delaminated to me, but i could be wrong. Someone also relocated the bolt holes for the motor, which further leads me to believe someone messed with the transom prior.
Would an angle grinder be the correct tool to begin cutting into the transom? Any other tool you would recommend?

Plan for power at this point is a Yamaha 70 4-stroke (~250lbs). Performance wise, id like to cruise mid 20's and top out at about 30 with 2 people and full cooler.

[RickK]

I first thought that the transom had been redone but then decided no one would have done that bad of a job. Maybe they did.
Reason I mentioned grinder was to grind down an area and see what was under the gelcoat before diving head long into a full transom rebuild. If you found poorly bonded glass then you'd know it all needed to come out or at least be refinished. If they did that poor of a glass job, the core would be suspect too, in my mind.
Seems your plan is to preserve the finished inside of the transom liner - correct?
If so, my approach would be to figure out what happened to the transom - maybe start with a 6 or 7" 24 grit flap sanding wheel on a 7" angle grinder and take all the gelcoat off the aft side of the transom and look at what you have to do. A large flap sanding wheel will make short business of that gelcoat and also keep the gouging to a minimum- you're going to have to do some grinding on it anyway.
If you're not trying to preserve the inside liner then I would work from the inside instead of from the outside. First thing I would do is make a drawing of the inside of the boat as it currently sits. Lay a straight edge, like a 2x4 or 2x2 aluminum pool cage support, across the top of the gunnels and measure from the straight edge to the current floor. Measure every 12" from back toward front. Also measure width (beam) of boat every foot. The drawing will help you document everything you've done and know what things were like before you did any work. If you cut out the floor, add the stringers to the drawing and measure to the tops every foot, measure from one side of the hull and mark the bottom and top of each stringer. So if you measure from the starboard side, you'll have the a complete drawing of where everything below the new floor is for future reference, you'll be glad you did. For instance, if you raise the floor by adding to the stringers, add that new info to the drawing.
If you decide to work from the inside because the outside transom skin is to far gone then I would mark 18" from the outside of the transom, and that would be my cut line across the gunwales, down the liner, across the floor and stringers. If you do a clean job with the cut, you can reglass everything back together after you rebuild the transom. You'll want at least 18" of work space in front of the transom to get a good bond of the glass to the sides and hull bottom as you overlap the glass.

[AquasportEd]

Rickk,

I am not trying to preserve the liner, or much of anything haha. Basically im preparing myself for a full rebuild (transom, stringers, deck, tank, paint, etc...).

The reason I mentioned going from the outside of the transom is because i figured that was easiest (most access). Again, more or less regardless of what i find after removing the skin of transom, the plan is to remove the core and rebuild it. This is mostly because I can almost guarantee the foam is saturated in the stringers and the deck appears soft and is planned to be replaced with a honeycomb type product. It doesn't make sense to me to replace the stringers and deck and not have 100% confidence in the transom.

I also figured it best to do the transom repair first, so as to retain some hull integrity prior to removing the deck/liner.

 

[RickK]

You're right.
That being said my recommendation now is to do what I mentioned above about cutting everything out 18" from the aft of the transom but be careful so you can re-use what you cut out and don't forget to get all those measurements - a few years from now you'll appreciate knowing, for example, what space you have under the deck and where if you wanted to add a storage bin etc. My next thought would be, once all the cutting is done, including gunnel cap unless you can remove most of the screws on the shoe box joint of the cap to hull so you can lift the gunwale/cap up and stuff a 2x4 or something under it to avoid cutting, is use a circular saw and cut 2" wide strip into the transom from the inside and then use an air chisel to peel away the core down to the outer skin. Before the next step use a 1x2 or something and screw it across the top of the hull sides a couple feet from the transom, to hold the shape of the hull. I'm thinking it will be easier, once you get most of the core removed, to cut the transom out of the boat leaving a 2" lip around the hull sides and bottom. Sounds shocking doesn't it? What this allows is to lay a sheet of melamine against the back of the hull, secure it, and use it as a flat template for your new flat transom. The outside will be nice, smooth and won't need a lot of fairing. If tied into the hull bottom and sides correctly it will be as strong or stronger than the original - that's why we need 18" of space ahead of the transom to work.

When you are rebuilding the transom you are actually moving the low point forward in the hull.
Here is a link to where I explain the thought of the PVC pipe
http://classicaquasport.com/smf/index.php?topic=13148.msg133124#msg133124

Here is a link to where I show what is actual problem
http://classicaquasport.com/smf/index.php?topic=13148.msg133556#msg133556

Here is a link to Hawgleg's rebuild that shows the PVC pipe installation to keep a drain at the new low point of the boat
http://classicaquasport.com/smf/index.php?topic=13148.msg134262#msg134262

Hey, we're here for you - we have plenty of Master Rebuilders that can jump in here to add some advice as you go through this. I rebuilt my 170 over a 7 year period and I gutted it totally, all the way down to the bare hull. Here is a link - it's very long but has a lot of good ideas and process challenges in it that I overcame - https://classicaquasport.com/smf/index.php?topic=10101.0

Unfortunately I thought of the PVC solution after my rebuild 

[AquasportEd]

Rickk,

Really appreciate all the advice here, and I did have some time prior to this thread to look at your restoration, awesome job!

Time permitting this weekend, i will take your advice and get some measurements. Also hopefully mark out the 18in from the transom and get to cutting.

Circular saw set to a fairly shallow depth the best tool to cut across the gunnel/liner/deck?

[RickK]

I used a Bosch jig saw with Sterling blades.  The blades are not cheap but they are great for cutting fiberglass and last a while.  Use the circular saw for cutting the  transom core into 2" strips. Harbor Freight can be your best friend during a rebuild.
Take lots of pics so we can follow along and help where we can.
If you are going to stay with a notched transom take good measurements before you cut it out.

[AquasportEd]

Didnt get a ton of time to work on the boat over the weekend, but i was able to remove the last 18in of the deck/liner. Overall the boat seemed in better condition than i thought. Foam in the stringers appears dry, and from what little i can see of the transom core appeared dry. But core of the floor was saturated with water. I took a closer look at our "wavy" transom and Im now of the thought someone has patched in a repair section, as the shotty-ness appears about 4" in of both the port and strb side, time will tell.

Guess the next step in my plan is try and remove the transom core. You mentioned taking measurements then using a circular saw to cut 2in strips (im assuming horizontal). Should i do this setting a depth to hopefully not cut through the outer skin? Im also guessing I will have to remove some of the stringer to access the lower portion of the transom?

[wingnut]

What is the gray stuff on each side of the transom core? I am wondering if they waviness is from a badly poured transom (using Arjay or similar)... Have you gotten a look at what the transom core consists of yet?

[AquasportEd]

Good question, i noticed that as well and was not sure. The only part of the core that I can see is in the top corners, and that is solid wood, but i havent seen the larger sections of the core yet. Good catch, and based upon the uneven-ness of the prior repair a pourable transom wouldn't shock me.

[RickK]

That's the "leakage" they warn about when using composite pourable material. Does it look like the top edge of the transom has been replaced? If you remove the bolts going through the transom, what do you see in the holes? Based on what you're seeing now, I'd cut the transom out and do it right.

[AquasportEd]

just looked at the transom again today after work, and id have to agree all signs point to pourable. The bolt holes appear to show it as does the perimeter from the angles i can view.

Any ideas on how to tackle this? It seems to shear fairly easily, and the reciprocating saw i used to cut out the deck goes through it as well.

[wingnut]

I’d go around the transom edge with your saw (circ, reciprocating, etc), leaving a 4” flange around the edge. The remaining pourable compound along the edges should come off pretty easily with chisel and mallet, then clean up with a flap disc. You’re right, the compound is not super hard to cut or shear.

Once your transom flanges are clean, pick a core material and follow a build thread that matches your plan!

Make sure to take a bunch of gunwale width measurements before you cut!