transom ?
 

Replacing transom on my Pantera. I have plenty of glass experience and do everything old school still. Was planning on a good marine ply and ve resin. Buddy of mine trying to talk me into using epoxy and coosa board. My question is, is coosa worth the extra coin?

No, not for the transom.

Go old school

Are you going to a bravo drive ?

Yes, Thats the plan. Also, gonna raise the x while Im at it.

Not an expert but for what it is worth, Velocity used coosa board in the transom on the VR-1 and other models.

Padraig

Is your transom 2.75" thick?

What I was told, is that if you're going to run modest to big power you have to use plywood for the transom and engine stringers. Anywhere else you can use Coosa. I'm about to glass in my new transom, and I'm using 3 layers of 1/2 marine ply, with a layer of 24 oz woven roving in sandwiched between. Then to actually bond it to the boat, Core Bond B70 and 1708 glass.

If you asking about the VR - 1 I don't know what the thickness is. I can't measure as she is in hibernation.

Padraig

sounds like a glass dave transom recipe, and the best way to go !
have an x dimension all picked out yet ?
trs boat bravo conversion ?
how long is the engine room from transom to bulkhead or seat back ?

It appeared to be two 3/4 ply laminated together. believe Im going to go with Marine ply and Ve resin. Using 1.5 oz mat and 1708 which is my goto combo anyway. I just cant justify the cost of the coosa board. Normally I would just use poly resin, but I think Ve is a step above poly and just as good as epoxy in my situation. Im doing Trs conversion to Bravo setup and I think I 've settled in on a 2" higher x dimension. Certainly open to suggestions or reccomendations or personal experience on this one. Not sure on distance between seat and transom. Didnt have much space in front with the trs setup, so looking forward to gaining a few inches there.I'm usually an outboard guy.

It appeared to be two 3/4 ply laminated together. believe Im going to go with Marine ply and Ve resin. Using 1.5 oz mat and 1708 which is my goto combo anyway. I just cant justify the cost of the coosa board. Normally I would just use poly resin, but I think Ve is a step above poly and just as good as epoxy in my situation. Im doing Trs conversion to Bravo setup and I think I 've settled in on a 2" higher x dimension. Certainly open to suggestions or reccomendations or personal experience on this one. Not sure on distsnce between seat and transom, wasnt much clearance with current setup. looking forward to gaining a few inches.I'm usually an outboard guy.

Some things to think about
17 1/2 X up to 18' and maybe space back down
When you mount your transom assembly. Bravo Hp preferably, Get a ITS input shaft and mount the motor seven inches forward from standard on the assembly location.

If you need an ITS input shaft, let me know. I have one that is in excellent shape. that I no longer need.

heck yeah move it forward, specially if you work on it yourself.
was this boat borg warner or merctrans ?

search "moving the engine forward" oso thread.
there are a hand-full of threads on the subject, and start posting some pics as well, everyone loves a good build thread

I have an Hp assembly, Im using and It has/had a merc trans. What are the advantages of moving it forward the 7"s ? That would probably almost put me back to where the trs setup was. What is the factory x measurement? Im assuming 16" or so. Havent figured out how to post pics yet. Class 6 is your name Dan
I believe its your old boat. i bought it from lake george.

unable to post pics for some reason.

Yes it was

outerlimits doesn't use any wood at all, I don't think I've seen a boat come out of there in over a year with less than 1100's

the reason for moving the engine forward is balance (longitudinal center of gravity)
i do not have any seat time with this set up and therefore cannot prove or report how it would perform.

however,
based on reading what the race boat guys say on the subject of balance, ballast, and finding cg on a boat,
it was a matter of knowing (by reading) who spent the money, did the testing, made changes/modifications, who race
or who has raced, and then put their findings out there,
the engine in my boat gets installed 12 inches forward on an imco input shaft based off the above info.

as example a link and a video (the video in case it doesn't link) is the plum loco pantera, it's the go to video of video's for a balanced
good running boat. time of the video, it was powered by a small block moved forward with a driveshaft.

https://www.offshoreonly.com/forums/...cing-boat.html

Damn thats running smooth. I would imagine I would have the space , since it had a transmission previously.

How do you move the ending forward with a Bravo transom assembly? Doesn't the engine bell housing mount directly to the transom assembly? "Inquiring minds need to know!"

Great read. Im gonna put in the setup as stock and see how it goes. boat runs pretty flat now. I will be adding more power next year and make the adjustments at that point.

if the trs exhaust that came with the boat is acceptable, save it unless or until you decide not to move the engine.
if you still have the merctrans laying around measure from the center of the rear mounts to the flywheel cover / block
mounting surface.
the bravo measures 4 inches, the difference will tell you how far the engine gets moved back on your conversion
post the info, would like to know how much farther back the engine goes from merctrans to bravo

sonic24, you would use a front and rear offshore plate, or with a full fledged bravo drive line you could use either the plates
or 4 pedestal mounts as the bravo drive line bearing housing has the provision for mounts that go on the rear pedestals.

I have stainless marine exhaust. My merc trans did not mount to the back mounts used the yail piece and rubber bushing. but I certainly could get a pretty.close measurement. From back of block where trans meets the block is 12" which would move me back 8" give or take. I plan on moving all the hardware to the seat back, that should offset some of the weight....Wish I could post some pics. got a quite a bit of grinding done today.

the other thing i noticed just now on that video, starting at 1:51 the boat leaves the water 4-5 times but the prop is still in the water
and the throttle is still on,
makes me think the 4 3/8 prop-shaft height i went is a little high.

Why is there some disagreement about using coosa board.Some people on one of my post said that using coosa board is not good for transoms only wood.Are they just old school thinkers?
I read about in the past people laminating coosa board together to make a tansom maybe before the selection of coosa board was different then today, but we just installed a solid 2 inch thick coosa board tansom in my 39 foot catamaran and I want to know what is the problem with using coosa board.It has no wood and can not rot and it stronger than wood so it should be better.This is my build restore

https://www.offshoreonly.com/forums/...tor-build.html

What I was told, when I inquired about coosa, was that it would fail in high HP applications. Again, fine for mild power, which I assume is 600 or less, but for big power it will not hold up. This is second hand info, as I've never used it, but I 100% trust where I got the info from. For my boat, I'm replacing the transom with marine plywood, VE, and 1708, and I will have 1100 hp x2 in front of it.

I have been doing transoms for probably twenty five plus years now and truthfully i will say there is a place for composite transoms and i have done several but for my applications in high load high torque situations i just dont feel it can handle the repetitive loading and unloading of compression and tension at the top and bottom of the transom assemblies. I have had three race boats with composite transoms and all developed issues that were a direct result of them being composite. The 37 Talon i raced with Ed and Cleveland construction developed stress "eyebrows" above and below the transom and was always an issue that only got worse through time. The 38 Fountain SV i raced with Dean and Wahoo flexed so bad it actually wrecked a brand new pair of Herring six blades first time out and there was plenty of room between at the get go, that boat also developed stress related issues around the drives. We found out later on that boat had a long history of wrecking props. The 30' AMT DW with Dean and Wahoo also had major flex issues with the transom but in defense of that boat it was built as a lightweight kilo boat and was never meant as a rough water boat (it truly was a fantastic running hull). I also have a 34' cat with a composite transom that is flexing and developing those tell tale eyebrows. The few transom i have done were on mid range performance applications and i laid them up in three layers of half inch with a full layer of 22oz roving in between each layer, ordinarily i do not use an old school fabric like that but in these cases ,because of the linear weave of the fabric, it helps establish a very stiff end result. It is also imperative when using foam boards that an advance resin system be used, a VE at the VERY least. My thoughts are this, and i will openly admit i still carry some old-school-ness in my ways but its not without well earned experience. For me, they flex to much and have there own unique set of problems to deal with that i dont care for. The rotting issue is almost a moot point unless you are going to spend all that time restoring a boat and then leave it in the water for its whole life or leave it outside to fill up with water untended. Wood does not rot because it is wood, wood rots because of how its cared for or how poorly it was installed in the first place. My transom are installed in a way that no water can ever come in contact with any edge or surface of the wood and all rigging is well sealed and maintained, all ends and cut outs are capped and encapsulated. I am not adamantly opposed to composite transoms, i just dont care for them and have valid reasons based on what I've seen and the fact i understand the product limitations. I have done several builds where all but the engine stringers and transom were composite and they were fantastic boats that i know will outlast all of their owners, i love working with the stuff as it is so easy to cut and shape and so forth but you do have to think on your feet throughout the process.

yep . . . that would be a high load high torque application :D . . . three layers of half for sure . . . especially if you have boxes

I can say even for mass production rec boats as many have gone all composite. one vibration is felt more and depending on production power one can feel some flex, also noise levels are louder, ie waves slapping, engine transmitting noise thru basically the hull cavities. Some of the composite lay ups seem hollow to me.

Wood dampens vibrations, seems better for sound deadening, wood floats, would holds screws better, so it does have some positive factors.

OEM Mercruiser for bravo transom assembly installation --- transom thickness a min of 2 in max 2.25 in.

2.75 thick transom - stock bravo transom assembly and stock inner plate installed --- one could not install the nyloc nuts properly on the studs.

Composite transoms always seemed that way to me to, like they shudder when you go into gear.

The transom on my Pantera is 2.75 thick. From Pantera

Now I feel bad about having the transom filled with coosa. But I am hoping that the experiences you have had are with another type of coosa meaning not a solid 2 inch thick piece maybe 3 layers of 1/2 inch coosa board?I have 2 in solid with 4 layers of glass behind the coosa to stick it a.But if this is a mistake it is better for me to pay more to have the work re done.This is sad because I listened to someone say this was the way to go , someone who supposedly knows and more Fiberglas on the front side.

everyone on this forum thinks coosa is good for transoms
https://www.thehulltruth.com/boating...osities-2.html

Also I heard that formula and Outerlimits uses coosa in the transoms from the factory

you will be fine, it really is a great product and in most cases you'll never have an issue. My cases were race boats and run very hard, i personally still prefer a quality marine ply for transoms and stringers. I run my stuff very hard at times and just dont care for the way composites flex, especially the solid sheets thats why i laminate in layers of half. In your case with your cat my only concern would be what resin they used and that it was properly installed. With composite panels you really have to use an advanvced system, vinylester or epoxy. Poly does not bond well and elongation is far to low for it to bond to the foam proper. This is actually one of those topics where there are many sides, most guys will argue the benifits and i agree with nearly all of them. My only reservation is with high load high performance applications, we can experiance some issues over time, high performance boats can be a bit of a special case. I really would not worry to much about your boat, get 'er done and enjoy :cool:

most factories do use it now and its the only way to go in this day and age in new boats. For my application and for how we run these things (or how i do anyways lol) i still prefer three layers of half. The other thing a lot of guys dont realize when doing stringers in composite is you can no longer just through bolt engine mounts. You have to "shoulder" the mount somehow to take the shear load off the bolts. They will oval and shift quickly in the rough water offshore environment.

for Mercruiser ? and using a STOCK bravo OEM transom assembly with stock mounting stud lengths ? Basically anything 2.5 and up for transom thickness, the stock installed studs would be too short - one would have to install longer ones in a stock Bravo / Alpha transom assembly. And with any thicker transom, if the stock exhaust Y pipe was used, that would throw all that out of placement as well.

Info from OEM Mercruiser engine installation guide for Bravo and its the same for alpha's. I had to search for this info as how I could post it up here on oso. Its fairly current info below in the link..

Just saying - Back in the day we would have to install in new boat lines engine(s) & drive packages. New hulls without the transom even cut as the dealers picked what engine packages were going in from Mercruiser - OMC - VOLVO - Yamaha - sterndrives.

https://forums.iboats.com/filedata/fetch?id=7077691

Well that sounds better if it the boat can still be usable.But I appreciate your help and comments because there are not many sources with good information and less about performance boats.
I want to make sure with you,The boat is with 4 layers of glass starting at the back where the ground down fiberglass skin is and there is a 2 inch board of coosa and then there will be another 4 layers of glas hopefully will be about 2.5 thick.The drives are #6 dry sump
http://i.imgur.com/aGgdyKy.jpg

http://i.imgur.com/vmd2TE5.jpg?1

Looks like they need to grind it alittle cleaner , and more for some wider tabing.

like i said you will be fine, its a great product. My biggest concern would still be with resin, fabric choice and that its being installed properly. the four layers on each side are gonna help stabilize the surfaces and help prevent compression issues.

I'm going to add this for composite vs wood. Long ago, or so it seems, I was a manufactures rep in the ski/snowboard industry. At the time I worked for Atomic Snowboards. We used a wood core in all of our boards. At the time Rossignol started using the THC core. This was a foam core with Kevlar and carbon in it, very similar to Coosa board. For the average person this core would work just fine. I myself hated it, it felt dead and un-responsive, but it was a little lighter. Put this same core under an olympic athlete, and good luck. When Bode Miller went from Fisher to Rossignol he was snapping ski's. I don't think he was able to finish a run with out the skis breaking, I believe in the end, they ended up getting him wood cored skis. That was the last year he used Rossignol, the next year he was back to wood core skis and Atomic.

As Dave has said, composite has its place, but high performance, high load is not one. Wood is made to flex and hold its strength, it is a tree after all. Foam cannot take constant flexing and hold up, and least none that I've seen.