Ditto.... I had some deflection on the fiberglass over the transom ply on the 85 HD 20 i/o back in 2012 when I was replacing the transom plate for the out-drive and the shop used a 1 1/2" hole saw to do some exploratory cores (but could have used a 3/8" and found the same). Like Jim indicated, go from the inside and drill ~1/2 inches into the ply beneath the fiberglass; I would do two sets of holes on each side of the engine at 2" above the deck and 8". Look at the drill cuttings and if they are dry, great but if they are moist, be prepared for a transom redo. There is a lot of torque placed on the ply of the transom plate, not just on the engine stringers. Mine required the engine stringers to be changed out as well to a tune of ~$3,800 but it is a true HD 20 i/o so I did it to keep it on the water and out of the landfill. My $0.02, Kevin- If you review this link there is some pics and discussion regarding the forward steps and back steps. Old boats and old cars will test the wallet. http://www.hydrodyners.com/forum/index.php?threads/1985-hydrodyne-20-i-o-restoration.1673/
Thats exactly what I was going to say Except depending on what you find dont seal the holes because if you find rot there is no reason to seal. If you find rot the transome is shot and you have to do what I am doing in my thread "1972 Keel Up Restoration". If the small holes you drill produce moisture it is all over. New transom. If the small holes produce nice wood shavings you are OK. If the small holes produce dry weak wood shavings that you can crumble in your fingers your rot is there but just dry. New transom.
well holes were drilled and my heart was broken. core is good as some of you had said and the transom is rotten as the other of you had said. we drilled the first side (starboard) and the wood was so good practically like new. I was fist pumping and high fiving until we drilled the first hole in the other side. nothing there but black dust basically. I knew it was a gamble but was really hoping for good news. but oh well here we go. did some asking around and found me a body shop man that deals only in boats, so gotta go see him again tomorrow afternoon and see what the damage is gonna be. he did tell me today that the price was gonna make me cry. but just so happens at the shop in the back of a dusty dry boat storage building I found two more hydrodynes in near mint condition today, neither for sale or trade because I asked. but one is a 20' with a 200 hp mercury outboard and it is beautiful the other a 18' that used to have twin 150s on the back. after seeing those I knew I had found the person to work on my boat. he also told me of two more HDs here in town. hope one day probably next year I can get in touch with these people and take a little ride down the river with them. have one question for those of you that have converted from I/0 to outboard. what are the reasons-advantages to that? make it two. would it be worth trying to put my fin back on, its missing. or is not even possible. thankyou
Yes you can replace the fin. I converted mine years ago. They were not so rare then. It reduces the weight about 600 pounds which increases performance at all speeds. Less draft and better handling, but the I/O's are getting rare.
There is an easy modern way to replace a transom. Take the boat to a boatyard or boatbuilder and they will cut the top of the transom off and then get all the rotted wood out - leaving the inside and outdide fiberglass. Then they pour the magic transom stuff in and let it harden. I have not had experience with this but I read about it on the web and it would be easy for you since the core is good and would save you from pulling the deck. I would check the core in several places because as is the case with your transom rot can be there but not everywhere.
yea we checked the core in three spots sides and middle basically only where the floor and flat floor stringers were rotten and near where fin was though but your totally right wouldn't hurt to check a few more. im gonna look into that transom stuff though sounds like that would be the way to go but probably under the right circumstances also. has anyone on here run their boat with the fin and without the fin. what difference can you actually feel. because It used to be on there when I previously owned this boat but when I was checking transom I looked down the trailer and hull and it is missing now and really now sure what kinda damage may be down there either.
I would not use that fix, it does not solve getting the deck out of the way which is the biggest Job.
would there not be a way to just take deck off, leave outside fiberglass of transom and just tear out inside glass and all wood from transom, replace what looks like two layers of treated 3/4 plywood and reglass the inside and whatever else you tear up. just been thinking on it wanting to tackle this myself but want some opinions from ones that already know what im fixing to get into fin missing has really got me paranoid now. hoping all is well and will put one back on I suppose. will help with pulling boat around when slaloming
