Need to extend my transom, but... there are too many ways to do it!

[crabbie]

I have an 18' Campion fiberglass runabout, pretty standard, and I've bought a really nice 4-stroke for it, but wouldn't you know the motor is 25" and the transom is 20". So close, so close.

So, I need to raise the transom a bit. Not such a bad thing, and I'm kinda handy -- though by no means a seasoned boat restorer -- but, sure! No problem, right?

The transom itself I *think* is essentially sound. I assume it used to be perfectly straight across, but after 25 years or so it's only bowed out 1/2" at the centre, which I'm assuming is not SO bad. And it has minimal rotting issues: I cut the top lip of the deck off to have a look, and other than some really minor bits the only rotted area is off to the side and about 5"x5"x0.5", which I can just fill.

So the transom is probably okay, but... that still means I have more than a few options:

1) have someone weld me an extension, with big wide surface area on both sides of the transom to bolt through, and raising a 14" or so section 5" above the transom.

Pros: Minimal work on my part, would be really strong, but...

Cons: not the best looking solution, and I need to find someone to do it


2) clean out an inch or so of the existing plywood and laminate some plywood together to span the splashwell, then glass overtop; turns out the lowered part the motor sat on is exactly 5" lower than the rest of the transom, so this would just make a nice level top

Pros: can do this myself

Cons: strikes me as a bit... weak. I envison a heavy motor with lots of torque mostly attached to the nominally-attached 6" piece of plywood extending above the existing transom... and my new motor sitting at the bottom of the Sound


3) pull the entire plywood section out (from the inside, presumably), laminate a new one, put it in and glass over it

Pros: strong!

Cons: a real pain to do... but in theory I could do it myself


4) go crazy with the chainsaw to remove the existing wood, the seacast it (a la this classic post)

Pros: strong!

Cons: more expensive, a real pain to do, and I'd be throwing away what appears to be a basically sound transom


5) only chainsaw out a few inches down, build a wood cast for the 5" I need to go up, Seacast only the top 8" or so, then glass over top

Pros: strong enough?

Cons: hmmm...


My original plan was to have an extension welded, then an "expert" I know recommended #2, but that's striking me as not so strong. So maybe the metal is good, but then reading here about Seacast maybe that's better... ARG!!! Too many options!



Any thoughts are appreciated, and I can certainly provide more details if I haven't explained it so well. I've been puzzling over this, my new motor is awaiting me in the shop, and the sun is starting to beckon me out onto the water... I need to get this resolved!

Thanks.

rodney

 

[oops!]

Re: Need to extend my transom, but... there are too many ways to do it!

if i understand you correctly.......you went out and bought a long shaft motor.....and the inti cav plate will be waaayy to low in the water....is this correct?


if so ........JACKPLATE !......

cheers
oops

 

[oops!]

Re: Need to extend my transom, but... there are too many ways to do it!

btw.....sorry bout the giants and as far as the nucks....nonas deserved it!

 

[ondarvr]

Re: Need to extend my transom, but... there are too many ways to do it!

It's not uncommon to have one made or make it yourself out of aluminum and bolt it together, it's not hard to do. Make sure the transom is in good shape though, it shouldn't have bowed out 1/2".

 

[erikgreen]

Re: Need to extend my transom, but... there are too many ways to do it!

Yeah, I was gonna say... jack plate. Unless the transom is cracked or bowed, in which case it needs to be done anyway.

If the transom is bad, then I'd do the traditional thing of pulling the inner skin, scoop it out, put in ply for your new 5 inch higher transom, and glass it all in.

Erik

 

[jcsercsa]

Re: Need to extend my transom, but... there are too many ways to do it!

Yep if it bow some thing is wrong !!! I know its a pain but I think redo the transom !! then the jack plate !! john

 

[tashasdaddy]

Re: Need to extend my transom, but... there are too many ways to do it!

your transom is failing. you don't say what size 4 stroke you bought. but it is heavier than what you are replacing. you can always add a jackplate. either bought or built. but fix the transom first, as the jackplate will add more stress.

 

[crabbie]

Re: Need to extend my transom, but... there are too many ways to do it!

Okay, there definitely seems to be a consensus on two things:

1. if the transom's okay, just get a jack plate welded up

2. the transom's not okay

So... I guess I'm fixing the transom!


Now, the idea of cutting a chunk out of the deck to get at the wood and replace the transom core with plywood really makes me uneasy. Not only would it be awkward to do, I really can't help but think the strength of the transom is compromised, though of course that just might be my layman brain being paranoid.

On the other hand, the idea of leaving the glass alone and replacing the plywood core with Seacast, I find that appealing. Getting the wood out is no doubt a bit frustrating, but I already have a chainsaw and two looooong bits, and I would be left with a transom that is essentially bomb-proof. Not only would it be SOLID, but there's no more chance of rot!

(BTW, yes, it will be a heavy motor: a 90HP Yamaha... then again, there was -- inexplicably -- a Merc 1500 tower o' power on it before, no doubt contributing to the bowing.)

While I'm filling up the existing transom, I may as well fill in the gap in the motor well at the same time, then I don't need a jack plate. Heck, with Seacast, I probably don't even need to bother with metal plates where the motor mounts! (Well, expect maybe for a small piece inside, where the clamps set on the glass.)

Anyone think I'm heading off course, here?

Thanks!!

rodney

 

[reeldutch]

Re: Need to extend my transom, but... there are too many ways to do it!

seacast is a good product.

the only thing is that the cost is so high.

its all up to you and your budget.

cheapest fix is to weld a custom aluminum transom plate.
will - beef up transom
- straighten transom
- raise hight

its not the nicest looking way, but cheap and easy.

if the boat is in real nice shape cosmaticaly and structioraly i would go with the seacast and spend the extra money.

 

[tashasdaddy]

Re: Need to extend my transom, but... there are too many ways to do it!

http://forums.iboats.com/showthread.php?t=206019

http://www.shareaproject.com/pages/projectTut,p,346,00.html

 

[jcsercsa]

Re: Need to extend my transom, but... there are too many ways to do it!

Hay crabbie, Thats a big drop in power??? I'm not the expert on this but isnt that pushing the lower limit of the boat ??? whats the boat rated for ?? I kind of hate to bring that up , but if it is you will use a heck of a lot more gas!

On the transom , yes it some work , but its not really that hard to do !! and if you ever laid dry wall tape , its kind of the same . the seacast is great on what I have read. but if you go with plywood we are all here to help also !!! if you can afford the seacast that a great , and it will out last anything else !! john

 

[crabbie]

Re: Need to extend my transom, but... there are too many ways to do it!

Yeah, it's a "loss" of power, but... it should never have had a 150 on it anyway, the former owner thought he was buying a used 115!

rodney

 

[oops!]

Re: Need to extend my transom, but... there are too many ways to do it!

crabbie....a 90 hp is too small for that boat......your goin on the ocean right?

the juan de fucha st?. over to gibsons?.....

you will need more power.

base minimum is 15 % of max hp.....a 18 footer might be rated around 150....

the max hp rating will be on the plate on the transom.....

you dont want to be caught out there with a boat load of people and too little power

 

[Robj]

Re: Need to extend my transom, but... there are too many ways to do it!

I would definitely deal with your rotting transom before doing anything else. The only real fix is to replace it, I am a big fan of using plywood versus Seacast, but must admit that I not used Seacast before. With Seacast how will you ensure a good bond with the existing when it will be so hard to clean out the rotten wood?? Plus Seacast is expensive, especially when you pay for shipping and duty.

You nickname, Crabbie, you stole that from a girl here at work. LOL

But seriously if you need a good plastics supplier here in Vancouver, send me a note and I will forward you some info.

Have a great day,

Rob.