Rebuilding Transom on 16ft Fibreglass half-cabin

[irishjim]

G'day Guys

First of all let me say that this is one of the best boating sites I have looked at, and that I consider there is a wealth of experience, talent and advice that boating people can tap into when an issue arises. Having said that, can I ask for advice/comment on the following issue

At the weekend I noticed some some slight movement in the transom of my fibreglass boat when swivelling the Merc 85hp up and down (non hyd tilt). I had some other boating enthusiasts look at the issue and the majority thought it highlighted a problem (probably some wood rot beneath the fibreglass) and that two options were open (a) have it repaired (b) buy a new boat. Option (b) is not possible at present.

Have any of you experienced the same issue and what other options were available. Someone else suggested bolting 3mm aluminium plates either side of the transon and installing stainless steel brackets from transon back to other side of transom well.

Could a boat repairer investigate the depth of the problem just by tapping the transom or other means?

Any idea on costs of having transom replaced if required.

I would appreciate any advice or suggestions you can give.

Regards - Jim

[gavsgonefishing]

Jim, depends what you want to do with the boat, how long your keeping it, what the boat is worth to you and the bucks available.

Without seeing a pic, my guess is if you have general movement in the transom, than she is stuffed. time to replace. Its not a major job if you have some basic skills.

If you do a search on transom up to a year in this section, that should give you several different projects that have been detailed.

Take the capping off on the top of the transom hand have a dig, if the wood is wet, its bad. Also take a screwdriver and have a scratch in the bung holes, wet, bad. Sometimes you can give the transom a tap and the hollow sounds or parting of the gelcoat means bad stuff. look around the engine mounting holes as well. Once you have determined its definately stuffed then its time for the motor to come off etc.

Happy thinking.

[billfisher]

Repairing a rotten transom is the worst possible job you can do on a fiberglass boat. People will tell you that the only way to do it is to replace the wood from the inside of the boat. This is a major operation and will cost thousands if you pay someone to do it. Alternatively you can replace the wood from the outside. I think that this is strong enough if you use the highly adhesive epoxy resins. The only problem is that the repair will be obvious if your gel coat has aged at all.
If different way is explained on the Rot Doctor site from the US. This what I ended up doing for the fraction of the cost of the above methods. It involves cutting the top off the transom and digging out as much of the rotten wood as you can. Usually only a section has gone rotten around the transom bung holes. You then dry out the remaing wood and treat it with a penetrating resin. This kills all the rot fungi and strengthens any remaining rotten wood by filling all the microscopic channels left by the rot fungi with resin. The wood is also now protected from future rot as well. You then drop in a new section of plywood using epoxy laminating resin to glue it in place. As you normally have two or more layers of ply in the original design you can create an overlapping join for added strength. You then epoxy the top back on and you can hardly tell that a repair has been done. I bolted alloy plate to the the inside and outside of the trasom using the outboard bolts for added strength. I used the International brand penetrating resin (Evadure) and their laminating resin. The Rot Doctor products are hard to get in Aust. and are too expensive if you can. The use of epoxy resin is the key to the operation. Its a very good adhesive both for wood to wood and wood to fiberglass. In fact if you have 2 pieces of wood epoxied together and you try to break them apart the wood will break first.
My transom is now solid as a rock and there has been no sign of weakness after 3 years. I wouldn't recommend just bolting plate metal only as a repair. Its just a band aid solution and the problem is just going to getv worse with the wood still rotting away.

[irishjim]

Thanks guys for your advice. I'm taking my boat to a repairer tonight for a free inspection to get his opinion.

However, I will also discuss the option put forward by 'Billfisher' and seek the repairer's opinion. I have a fairly large shed that houses the boat and a reasonable supply of tools, plus a reasonable level in general handyman skills.

I would probably be replacing the boat in 2-3 years and don't wish to spend extravagent dollars at this stage.

What is the web site for the Rot Doctor in USA?

Regards - Jim

[familyman]

Jim as gav said do a seach for transom,plenty of good info.Also look for 'Jeff webster's second hand boat secrets'in the newsagent .Gives a step by step guide to replacing a transom from the outside.
Alternatively you could just do the transom form the outside and get someone to fair and paint it to suit the existing colour.But be warned ,long term the best way is to replace the WHOLE transom not just the rotten bit.Look for a post by fnq cairns,use the link to share a project .com.Good luck.
cheers jon

[blaze]

I believe that the only way to do a transom is to remove the outboard well and the inner skin. I think you also need to remove enough of the floor (18") to also tie the new inner skin to the stringers. The only place that takes a bit of finishing is putting the well back in. Its well and good to talk about just doing the transom but IMO the floor/stringers will be showing signs of the same rot that has got into the transom. Apart from where the motor bolts on the biggest cause of failed transoms appears to be the drain holes as in the past they just drilled them in and left the timber exposed so when people left there bungs in and the boat filled with fresh water the only thing it could do was leach up the timber inner of the transom.
cheers
blaze

[billfisher]

Jim,

If you put "Rot Doctor" in your search engine you should find the site. Another bit of information I saw on another site was that someone in the boating industiry doing an informal survey of fiberbglass boat repairers. He was expecting to be told the the only way was to repair it from the inside. Suprisingly the majority said that it was just as strong (and a lot easier) to repair it from the outside.
Also a repairer told me once that the professionals sometimes only replace a section of the plywood. This is what you are doing by the Rot Doctors method, but by going in from the top makes it much easier for the home handyman.

[Always_offshore]

where about do you live?

[blaze]

I suppose its down to personal opinion, but pray tell how you can successfully laminate a section of ply into a average 30mm gap on say a 20" transom, that means that you need to get down 20" in a 30mm gap and clean out the rotted wood and roughen up the surface to get some mechanical bond on the old inner and outa skin and ontop of that you are going to shape the perfect piece of new ply to slot down there and when doing the final fitting there will be np pockets of air (hard enough sometimes to get the air out off a section of mat on a rounded surface at times). I would think this method of repairing a transom would be the prefered cheap method if you was selling your boat and trying to maximize the $
Again only my opinion and not having a go at any one
cheers
blaze

[billfisher]

Just offering my experience Blaze. I have done it this way and this system works. The rotten wood is soft so its very easy to dig out. A long spade drill is handy as it chews through the wood and bounces off the fiberglass. I use a chisel bar for the rest of the wood and is was easy to create a straight edge and measure up the new section. Also as you are creating an overlapping join the measurements don't have to be dead perfect. By the time you have ripped all the wood out you are well on the way to creating a rough surface on the fiberglass. If you coat all the surfaces with plenty of epoxy and rig up a clamping and pressure arrangement you shouldn't have a problem with air pockets, especially on the important inner surface.
Obviously replacing all of the wood in one piece is theoretically stronger, but in practice this system seems plenty strong enough. I think it is beyond the abilities of the average home handyman to replace a transom from the inside. Also this way generates huge amounts of dust which will not put you on good terms with the neighbours! If you pay for someone to do it this way costs around 3000 dollars, a lot to spend on an old boat.
Also remember that often the rot hasn't got that far. In my case it started with the drain hole on one side of the well. So after replacing the rotten section half my motor is bolted to the original (still sound) wood. Also the metal plates add a lot of strength and spread the forces away from the join.

[gavsgonefishing]

I'm for replacing the whole transom if you want to keep it for many trouble free years. whether you replace it from the inside or our is a matter of choice. You know then that ALL of the transom is sound, and there are no pockets of surprises left for latter.

Although I have not done a transom billfishers way, my guess is it is a little harder than just scratching the existing stuff out. Even with a grinder and hacking into an existing transom with a heap of room and grunt, its a major job. The easy bits is putting the new one back in.

Blaze has hit it on the head with starting from the inside out, because sure as there may be some ( hopefully minor) damage to the stringers ajoining the existing transom.

Familyman also had a good ide, you do the hard stuff and let the pros finish off the shiny stuff. A lot cheaper for you with the pro finish.

Hope this helps

[billfisher]

Although I have not done a transom billfishers way, my guess is it is a little harder than just scratching the existing stuff out. Even with a grinder and hacking into an existing transom with a heap of room and grunt, its a major job. The easy bits is putting the new one back in.

I don't know about my way being a little harder. Doing it from the inside before you even get to the timber you have got to cut part of the deck and floor off. Then you have to grind away all the inner transom glass which is typically 1 cm thick. All the fiberglass dust you generate is a major problem. Then you have to grind away all the good wood (which is much harder to do than removing the rotten stuff), without damaging the outer glass. Once you replace the wood all the inner fiberglass has to be layed up. Then you have to re join the deck and floor and try to make it look reasonable. Its not hard to see why it costs around 3K doing it this way.

[cooky]

IrishJim - I'm sure by now you have your answer. You need to make sure your safety equipment is up to scratch, you have good lifejackets, don't go too far offshore (which you prob don't in a 16ft) and leave your boat as is . Who knows you may get 2/3 yrs good operation out of it - then upgrade. Sell it to someone who wants a good project (plenty of them out there).

I like the sound of the Rotdoctor type solution with aluminium plates. If your boat isn't worth that much to you (depends how old, etc) then this will certainly get you by. The others sound like an aweful lot of hard work and unless you're looking for a project........

If you work full-time and you've never done something like this before, it could be one of those typical male projects that takes 6 months or more or is NEVER finished. I've seen plenty of them.