took her under the knife (need some opinions)

[dcobbett]

I used Pensky Board when I re-did my transom and one thing I learned is that it's thicker that ply because it's made in metric dimensions. Not sure if Coosa is that same, but I remember thinking at the time that that would be a major PITA if someone used Pensky board doing a transom from the inside and then couldn't fit the old glass piece back in place.

[grgrmouse]

I've been admiring your project here. I've got a '20 Mako I'm finally riging after a loooong rebuild. Some of the issues you talk about I've dealt with as well. For instance, the weight transfer....moving two batteries under the console at 50# - 70# each, depending on the type, seems like it would easily make up for the new 'zuke. I moved mine forward as well. I went with the Trollfury setup. Both batteries and box are 134#. The thing to remember is now the run of the battery cables are 5x's longer than before.....
You need to upsize the wire (diameter) to account for the voltage drop and heat. As for the transom issue, I just helped a buddy do his on a Grady, I suggest using a piece of luan door skin to cut a template before you cut the expensive stuff! (lesson learned the hard way by many!) just my .02.. Look forward to seeing more pics.

[Bushwacker]

Skip said he used the 26# Coosa, which he got from Don Herman. If Don uses it, that's what I'd use! It's still lighter than plywood! I'd use 2 3/4" pieces as that should be closest to the plywood dimensions; test fit each piece before you stick 'em together.

One thing you have backwards is the way you lap the forward layers of glass into the hull. The first piece that lays up against the Coosa should be the longest, then each successive layer should be a little shorter. If you go from short to long, you're putting a kink/step in the longer layer where it goes over the shorter layer; this creates a stress concentration! Nature doesn't like kinks! May be a nit, but the devil lives in these sort of details, which separate the amateurs from professionals.

[McGillicuddy]

Dang Denny, you've got amazing powers of observation... thanks again for another subtle, invaluable tip...Here's a picture of the bolt on splashwell Bushwacker spoke of on an early response to this thread, this is from a 77 Seafari 20. Hopefully it's enough to get the jist...

[SonOfABeach]

bushwacker - Yup going with (2) 3/4" of Bluewater 26, glad to hear he used the same. Thanks for catching that, I can see now that it could create a stress point. So the last layer be just slightly larger than the transom with consecutively larger layers under that, 4 layers sound sufficient or should I beef it up and go with 5? Should there be any kind of mat or something between the layers or just need 1708?

McGillicuddy - Thanks for the picture! Something like that is exactly what I'm looking to do, good to know my brain is at least on the right track.

Buying the materials in the next day or two, should be getting to work on it later this week. Pictures to come.

[Bushwacker]

. . . So the last layer be just slightly larger than the transom with consecutively larger layers under that, 4 layers sound sufficient or should I beef it up and go with 5? Should there be any kind of mat or something between the layers or just need 1708?

4 layers is plenty. You might want to recheck Carla's post & photos, but I believe first layer went about 2' around onto hull; successive layers were about 6" less. The main thing is to achieve a gradually tapered thickness to avoid a sudden thick/thin transition. A sudden change in stiffness can create a hinge effect and a stress concentration. For total thickness buildup, I believe you can figure on roughly 1/16" for each layer of 1708, so you may have to trim the stuff you cut out for what will no doubt be a thicker new transom.

A layer of 1708 on the old transom skin (rough it up first) is probably a good idea to insure good bond between the original polyester and the new epoxy. Be sure to wash off the amine blush from any cured epoxy before putting anything over it. Most folks seem to use put a layer of glass/1708 between plies in the transom, but I'd check the Coosa and/or West System web sites to see what they recommend. The Coosa Skip used was about 2" thick so only used 1 piece. When you apply the cabosil before installing core, use a tile trowel to create a series of v-shaped grooves which will allow the paste to spreadout and hopefully achieve uniform thickness. It's also good to install some randomly placed (to avoid a tear-along-the-dotted-line scenario) ~1/4" "vent" holes to allow any trapped air to escape between core and transom skin. Good Luck! Denny

[SonOfABeach]

After shopping around for supplies (and actually setting up an account with a local company that only deals with boat builders, businesses, etc, moms educational consulting firm now has an "client entertainment ala SeaCraft" department , but saved a ton of money now and later, I'll never buy anything from West Marine or Boaters World again) and then waiting out a hurricane (hanna) and other random obligations, I finally got to work on my 20SF again.

While I was at work all day my dad was nice enough to do some prep work and lay down the layer of 1708 on the outer skin to thicken it up/prepare for the new core.





Then marked and cut out a template from the door skin, thanks for the tip grgrmouse was originally gonna go hunt down a huge refrigerator box and use cardboard but the appeal of not having to jump in a series of dumpsters was overwhelming . Test fit and trimmed down till a perfect fit. Just look at that beautiful VDR Hmmm what to do with this thing now? Maybe a life size CSC 74 Potter Built CSC poster for the shop wall?



Then laid out the Coosa to get ready to cut. Really impressed with this stuff so far, extremely light and easy to cut. Extra money was worth it for the less weight alone.





Got both pieces cut and cleaned them up some with the grinder, only needed a few touch ups here and there.



Sun was going down and the bugs were coming out so called it a night. Hopefully getting them epoxied together tonight after work and installed in the next day or two after some fitting and cleaning up as necessary. Just bought a new DSLR "like" digital camera (not enough into photography to justify buying a DSLR...yet), so couldnt help but snap a few of her. I know you guys have seen a million pictures of these boats but I cant help but posting a few, its just such a beautiful boat, even with her backend tore out haha.







Thanks for looking all, and all the opinions and advice, great community here. Hopefully have some more complete pictures up in the next couple of days or so. Trying to get all this done and the boat to my local Suzuki guy for him to mount the engine before the 4th when I leave for New Zealand for 10 days, so the whole plane ride back I can be thinking about my usable 20SF at home waiting for me.

[SonOfABeach]

Made some progress but didn't take any pics unfortunately, amazing the stuff you forget to do when you're working against the epoxy set timeline .

Friday night got the Coosa laminated together (layer of 1708 and thickened epoxy) and let that set up over night, solid as a rock in the morning.

Saturday we trial fitted it and got her nice and snug and then drilled the weep holes, buttered her with with some thickened epoxy, put a generous amount of thickened epoxy along the bottom for her to rest in and set her in place. Tightened down the 2x4s used to clamp her in place and then cleaned up the ooze that was coming from the holes.

Sunday I sanded down and cleaned up the messy spots where the epoxy oozed over night through the weep holes and around the bottom. Also did a lot of staring and thinking, which is what I go to from here.

I've been thinking and losing sleep over what you guys said in the beginning, about going back to a 20" transom with the heavier 4s. I'm basically locked in to the 20" motor sitting in the crate in my garage though, the out of town outfit we went with for the engine has been less than helpful. I mentioned before about them trying to get another sale out of me the day after I bought it when I inquired about coming up and switching it out for a 25" (wanted me to pay the difference ($1300) for a 2009, because they were sold out of 25" 2008s where the day before when I picked up mine they had them in stock). I even inquired later about trading down to a 140 Zuke like most guys on here did and eating the difference but they would have none of it. They also promised to not submit the warranty info to Suzuki till I called and told them I hung the engine (being that I knew it would most likely sit for a month or so while I replaced the transom) so I wouldn't lose that time in warranty when its sitting in a crate, but last week I got my warranty card and a "Dealer Satisfaction Survey" in the mail from Suzuki, gonna be fun to fill that out.

So what I'm 90ish percent positive I'm gonna do is leave the transom closed in, install a bracket, mount the 20" on the bracket. I've been searching this and classic mako for any post with a bracket over the past few days, and have realistically spent around 20 hours reading them over the weekend.

I've seen on Hermco's site that his are made for 25" shaft only, so a Hermco is out. In fact D&D Marine is the only company that has instructions for installing for a 20" shaft motor. A guy over on Classic Mako closed in his transom and put a bracket from D&D on his 19 and reported that he was pleased with the ride and flotation, getting a waterline about 1" lower with the bracket vs directly mounted on the transom. The D&D bracket is 16.5" x 18" x 30" long. I also have found another outfit that makes a bracket very similar to the D&D one in design but is 15.5" x 15.5" x 26" long (which after talking to him he said he could fabricate one with a larger flotation chamber if I wanted). Would the 4" less offset be of more value being closer to the transom provided less of a throw to the COG, or do you guys think the 4" more inches of flotation space would be better because it offsets the weight of the engine more? I've read CaptLloyd's post on the modifications he made to his B-Bracket to get more lift and how in retrospect he would have gone with a bracket that provided more flotation to begin with, but I'm kinda locked in place with the 20" shaft.

What do you guys think is the better option? Cutting the transom back to the 20" notch and risk having the water dangerously close (if not up to) to the line of the splash well because of the extra weight (and like you guys said, possibly killing the resale value because noone wants a 20" transom anymore, although right now I dont ever see myself selling her I want to keep my options open), or keeping the transom full, installing a positive flotation bracket like from D&D (or from the other guy and having him fabricate one with a wider flotation chamber for more weight offset) and possibly have the boat ride a little off from being stern heavy. I have redone with transom with Coosa saving weight, moved the batteries to under the console, pushed the fuel tank all the way forward, and could put a couple gallons of freshwater in the anchor storage up front to help offset the weight if need be, later add trim tabs, etc). It all just seems like the wisest choice to me to go with the bracket and closed transom. I'm pretty sure thats how I'm going, and hopefully get some reassurance from you guys. I know I might run into COG problems from doing this, but which is worse, working out COG issues, or having my boat/engine dangerously close to the waterline with a 20" transom and still probably have COG issues to work out? Thanks for any input guys.

[hermco]

They make shaft extension kits for Yamaha,Merc,OMC,Evinrude,Johnson. I don't know about Suzuki.

[SonOfABeach]

yeah I've done some searching for that and all I found were extension kits for the ones you listed. couldn't find anything for Suzuki except a post on the hull truth with someone else looking for one and finally deciding that they didn't exist, I'll do some more looking into that before ruling it out.