1980 160 Seanymph Fishing Machine Transom Replace

Hi Everyone,

This is my first post, long time lurker though.

My family received a 1980 Seanymph Fishing Machine about 5 years ago and the boat has just sit. We are now looking to get it up and running. However, when we received the boat we knew the transom was in bad shape (I mean really bad). You could almost push your finger right through the wood. Without the transom saver the motor would most likely rip off the boat. A couple pics are added at the end to give you an idea. Fortunately the aluminum seems to be free of cracks or rips. However you can see how much the back end is bowed out.

We are going to fix this by ourselves and had a few questions:

1. What is the best type of wood to use? The current wood is 1.5" thick. Would laminate beam (like for structural support in a house) be as good as marine plywood?
2. What do you suggest to use to seal the wood?
3. If marine plywood is the better choice, what should be used to glue the sheets together?
4. Given that the motor that is attached to this boat is roughly 200lbs, would it make sense to place a steel plate (or similar) on the visible side of the wood to help reinforce?

Any help you guys can provide would be greatly appreciated! Once we have figured out the materials we need we will just need to figure out how to get the motor off the boat!

Re: 1980 160 Seanymph Fishing Machine Transom Replace

Welcome to the fray!

You don't mention it but first thing I would make sure of the condition of the motor. Could save a remount on your new transom.

Onto your transom,

For the motor dismount what little I can see of it I'll guess it at a 50 which once unbolted/disconnected two people can easily lift off. From there it looks like you have the pretty standard setup where you'll need to pull the corner caps, remove the top tin strip, and remove any screws. Then just pop the old wood out.(sometimes easier said than done)

For the new one any 3/4" acx plywood will work, just make sure it uses exterior glue and you'll be fine. Alot of us favore the Arauco plywood from Lowes(I got mine at Menards) No pressure treated though. Again going on just what i can see I'd say you could get it out of about half a sheet. It'll take laminating two pieces of 3/4" together to get your final thickness. From there seal with your choice of sealer and put her all back together.

That's the quick answer, I'd suggest you search out and read some of the threads as there are many ways to accomplish the lamination and sealing.

And if my guesses have missed by too far post more pics so we can get the bigger picture, there's a wealth of info here.

Re: 1980 160 Seanymph Fishing Machine Transom Replace

This is actually a pretty easy one compared to a glass boat. Unbolt the motor and if enough slack in the cables just lift if up a little otherwise unhook everything (rent a car engine hoist). Remove all the bolts through transom, drain holes, corner plates, and cap and dig out the old wood. You need a special tool to replace those aluminum drain holes but I think you can get some plastic ones that will do the job. There must have been a motorwell at some time, if not putting that back just forget them. I'd use 2 pieces of 3/4" treated plywood. I worked for an aluminum boat manufacturer, we used treated wood and never had a corrosion problem with it) and glue/clamp together with gorrila(sp) glue (used that in an I/O transom 10 years ago still nice and tight). I don't believe in sealing the wood so much because moisture WILL get into it. (I'm sure you will hear I'm wrong about that) I like the idea that it can dry out quicker after it gets wet. Then bolt it together with ALL SS fasteners. And get rid of that piece of steel and those steel nuts. Aluminum and steel don't like each other and cause electrulitic corrosion problems. An aluminum or SS plate is an OK addition but NOT steel!

Re: 1980 160 Seanymph Fishing Machine Transom Replace

Thanks for the replies guys!

@TruckDrivingFool: Thanks for the welcome! I already started a new thread for the motor. Basically this boat was a hand me down from a distant relative. The boat has not seen water in anywhere between 6-10 years. The motor itself looks clean but needs some fixing. That is definitely one of the top things we are checking first before moving too much further though! The motor is a 50 horse Evinrude (1997) and weighing close to 200 lbs. Even if we could get a few guys to lift it, I'm not exactly sure what I would need to make to be able to hold such a large engine. As for the instructions, thanks!, that's just what I wanted to hear. I'm sure I will run into a few issues here and there, but it is certainly within our realm of feasibility. From what I have heard and seen it seems like outdoor/acx/etc plywood and laminating on your own is the way to go (versus the laminated beam).

@Georgesalmon: Thanks for the tips, it's always good to hear from someone who actually worked for a boat manufacturer. I will definitely use Gorilla Glue as I have heard many good things now about that (is there a certain type that you specifically suggest?). The piece of angle steel there was an addition by the previous owner to try to reinforce the transom, so it will certainly be removed as well. Yes there was a motorwell and back deck as well, but we will need to remove everything and replace all the floors in the boat as well (as it is all rotted). This is certainly a large project, but the two main things we were worrying about were the motor and the transom, but I am becoming more and more confident that we will be able to get everything working.

Re: 1980 160 Seanymph Fishing Machine Transom Replace

Georgesalmon said:

I worked for an aluminum boat manufacturer, we used treated wood and never had a corrosion problem with it) and glue/clamp together with gorrila(sp) glue (used that in an I/O transom 10 years ago still nice and tight). I don't believe in sealing the wood so much because moisture WILL get into it. (I'm sure you will hear I'm wrong about that) I like the idea that it can dry out quicker after it gets wet. Then bolt it together with ALL SS fasteners. And get rid of that piece of steel and those steel nuts. Aluminum and steel don't like each other and cause electrulitic corrosion problems. An aluminum or SS plate is an OK addition but NOT steel!

Click to expand...

George, your aluminum boat manufacturer can probably still get the old arsenic pressure treated. Anyone buying wood at a home center should DEFINITELY NOT use pressure treated anywhere on their aluminum boat. The corrosion issue with the new copper stuff is seriously no joke. I'm not going to attempt to argue with you on sealing it.

flatlandy, as indicated, your transom project should be pretty straightforward. I've always removed my outboards with a cheap harbor freight come-along from overhead and just let them hang there till I was ready to remount. I went with the Arauco exterior ply from Lowes and sealed it with epoxy resin. The epoxy was also great for laminating the two pieces.

Re: 1980 160 Seanymph Fishing Machine Transom Replace

ezmobee said:

George, your aluminum boat manufacturer can probably still get the old arsenic pressure treated. Anyone buying wood at a home center should DEFINITELY NOT use pressure treated anywhere on their aluminum boat. The corrosion issue with the new copper stuff is seriously no joke. I'm not going to attempt to argue with you on sealing it.

flatlandy, as indicated, your transom project should be pretty straightforward. I've always removed my outboards with a cheap harbor freight come-along from overhead and just let them hang there till I was ready to remount. I went with the Arauco exterior ply from Lowes and sealed it with epoxy resin. The epoxy was also great for laminating the two pieces.

Click to expand...

Thanks for the clarification and tip! I wouldn't have guessed that the epoxy resin would be good for laminating as well, but that may a good path for me to take. As for the come-along idea, did you build something special to hang it from or did you have an existing structure (garage/etc)?

Re: 1980 160 Seanymph Fishing Machine Transom Replace

I have some 2x4 shelving in the back that has served me well.

You can kinda see it hanging from the come-along in this pic http://i176.photobucket.com/albums/w200/ezmobee/New Boat/DSCF2257.jpg

Re: 1980 160 Seanymph Fishing Machine Transom Replace

Hi flatlandy,

I did the same thing to my nympho about 7 years ago. I did what ezmobee said. It still looks brand new. I was going to sandwhich a piece of aluminum between the boards but I'm glad I didn't, it wasn't neccessary. I just had to tighten the tansom mounts once or twice after a few months and they haven't budged since, which is a suprise after cleaning a few props off!

Re: 1980 160 Seanymph Fishing Machine Transom Replace

Hmmm, I probably stand corrected about the PT. I was under the impression that the old stuff used copper sulfate hence the pretty green color. No real facts here. I thought the environmental folks outlawed copper sulfate in wood and bottom paint. I do know that aluminum doesn't like copper. I think we used a brand called "greenwood". Having read what you said I will probably change my opinion about PT. Just the regular original gorilla glue. Wipe the wood with a damp rag before you apply the glue, it is a moisture cure.

Re: 1980 160 Seanymph Fishing Machine Transom Replace

Another option for you motor is to lift it off and just lay it on the floor, front face down/prop up. That's what I did with mine.

I'll also 2nd the Gorilla Glue. Dampen both surfaces(the true key to using GG), spread a nice thin even layer, clamp it up/screw it together/or stack weights on it so that you get a nice even squeeze out, and let it sit over night. If you don't use the screw together method atleast put a screw or finish nail in two corners this will keep the halves lined up.

Re: 1980 160 Seanymph Fishing Machine Transom Replace

ezmobee said:

George, your aluminum boat manufacturer can probably still get the old arsenic pressure treated. Anyone buying wood at a home center should DEFINITELY NOT use pressure treated anywhere on their aluminum boat. The corrosion issue with the new copper stuff is seriously no joke. I'm not going to attempt to argue with you on sealing it.

flatlandy, as indicated, your transom project should be pretty straightforward. I've always removed my outboards with a cheap harbor freight come-along from overhead and just let them hang there till I was ready to remount. I went with the Arauco exterior ply from Lowes and sealed it with epoxy resin. The epoxy was also great for laminating the two pieces.

Click to expand...

When you say epoxy resin, are you referring to the resin you use when fiberglassing? Just without the fiberglass cloth?

Re: 1980 160 Seanymph Fishing Machine Transom Replace

Yes. There are two (main) options when fiberglassing: polyester and epoxy. Poly cannot be used without glass but epoxy can.