Your take on Transom Thickness

[Mercperk]

Background; repowering/upgrading a 1963 25 Bertram from the original 4s to moderns in the engine bay and from a Frankenstein PREALPHA starting at the gimble ring to alpha one gen 2s. I know back in those years 1.75inch transom thickness was acceptable but of course these years it's like 2 to 2.25 or something.
So what's my answer here this Bert has a super solid and super dry transom that's 1.75 inch thick.
Add fiberglass? Can you use a plate is some manner to shim essentially?
Will I be good? Just try to find the harder transom seal that SEI sells for some reason? Put 2 seals?
I read al lot discussion but still has me wondering.
Sincerely appreciate your time and consideration

 

[achris]

Pull the original drives, engines and transom assemblies. Glass up the hole completely (build up to the 2" required) and cut a single hole and drop in a nice 383 and Bravo Three drive..... More power, less drama.

Chris....

 

[Bondo]

Pull the original drives, engines and transom assemblies. Glass up the hole completely (build up to the 2" required) and cut a single hole and drop in a nice 383 and Bravo Three drive..... More power, less drama.

Chris....

Ayuh,..... I agree with Chris, 'n besides, if yer goin' from an in-line motor, to a V-motor, you'll most likely need to move 'em both, Outward, so they'll clear each other,.....

 

[Mercperk]

Pull the original drives, engines and transom assemblies. Glass up the hole completely (build up to the 2" required) and cut a single hole and drop in a nice 383 and Bravo Three drive..... More power, less drama.

Chris....

Yeah I probably should have but with a thought of originality and dual drive handling interest I just kept going with the 4s..... Plus I really am not good or efficient at glassing and building mounts for the mounts on a single from dual would have been an undertaken structurally.
Costs are coming in around 10k which is decent for onesided new and the other used and all new rigging. Where as that dang bravo 3 costs almost as much as a new 4cylinder. Not to mention what's the first thing that hits? The lower unit.... And that is replaceable if you have the money....
could've would've should've I suppose .

 

[Mercperk]

Ayuh,..... I agree with Chris, 'n besides, if yer goin' from an in-line motor, to a V-motor, you'll most likely need to move 'em both, Outward, so they'll clear each other,.....

I really do agree with y'all but hindsight is 2020...

 

[Mercperk]

I really do agree with y'all but hindsight is 2020...

They were inlines 4s then and they will be now.... Eventually......
I am confused Bondo with what you are saying outward? They are 26 inch on center

 

[kenny nunez]

When Yamaha was in the stern drive business I saw a 25 Bertram that someone butchered in a pair of V6 packages. The inside was cut up pretty bad. One look and I told the owner not to call me under any circumstances.
As what Chris said a 400 hp engine combination would work better than a pair of inline recycled packages. A local dealer has a 25 and is going to try a 300 Yamaha on a bracket on his 25 Bertram.

 

[achris]

Looks like your question has been side stepped. Partly my fault, sorry about that...

I would suggest getting the transom to the 2" thickness, either by added more glass on the inside or by using a custom cut ali shim.

Chris...

 

[Rick Stephens]

Not that hard to add 1/4 inch of fiberglass. Worst part is getting the old stuff clean enough since common practice was a rough inner transom surface. Lots of sanding if left in the rough.

I would want to firmly attach an aluminum shim, which I humbly consider would be harder to get flat and squeezed down tight enough that it wouldn't spring a bit over time and potentially allow movement at the gimbal housing. I could be mistaken, never made up an aluminum shim for that purpose.

 

[Scott Danforth]

They were inlines 4s then and they will be now.... Eventually......
I am confused Bondo with what you are saying outward? They are 26 inch on center

V-engines need about 34-36" on centerline

 

[achris]

Not that hard to add 1/4 inch of fiberglass. Worst part is getting the old stuff clean enough since common practice was a rough inner transom surface. Lots of sanding if left in the rough.

Agreed, any new glass needs to be added to the old glass only after the old has had the surface 'broken'. You can't add new glass to gelcoat or old glass because of the wax that comes out of the glass...

I would want to firmly attach an aluminum shim, which I humbly consider would be harder to get flat and squeezed down tight enough that it wouldn't spring a bit over time and potentially allow movement at the gimbal housing. I could be mistaken, never made up an aluminum shim for that purpose.

An ali shim would act exactly as if it was a thicker inner transom plate. Nothing to worry about it getting loose... Take a sheet of 1/4" marine Ali plate and the inner transom plate to a laser cutter and have them cut it...

Chris.

 

[kenny nunez]

Another reason for the 2” minimum transom thickness is needed to make sure the inner and outer transom parts do not “bottom out” against each other causing the inner plate to crack which will spread out the 2 vertical rear mounting holes. When that happens it is impossible to mount the engine.

 

[Mercperk]

When Yamaha was in the stern drive business I saw a 25 Bertram that someone butchered in a pair of V6 packages. The inside was cut up pretty bad. One look and I told the owner not to call me under any circumstances.
As what Chris said a 400 hp engine combination would work better than a pair of inline recycled packages. A local dealer has a 25 and is going to try a 300 Yamaha on a bracket on his 25 Bertram.

I only wish I had the money to do things the way these boats want to be outfitted

 

[Mercperk]

V-engines need about 34-36" on centerline

Yeah, one of the reasons that I stopped considering a couple 6s beyond all the other associated glasswork on a new doghouse. Those things sure are cheaper sometimes.
Spec these days in boat manufacturing at it's smallest is normally like 28 on center right? At least on inlines I suppose....

 

[Mercperk]

Another reason for the 2” minimum transom thickness is needed to make sure the inner and outer transom parts do not “bottom out” against each other causing the inner plate to crack which will spread out the 2 vertical rear mounting holes. When that happens it is impossible to mount the engine.

Gotcha thanks. Yeah that wouldn't be ideal. Is it acceptable in any scenario to add layers to outside of the hull with gel removed first.? As yes the inside of transom left in the "rough" seems like I'd have to go pretty deep to start in there

 

[achris]

I only wish I had the money to do things the way these boats want to be outfitted

Boats designed for stern drives NEVER perform well with 'after-thought' outboard pods. I don't care how good the owners say they are, every single PREVIOUS owner of a podded outboard on a previously stern drive powered boat I've talked to (and there has been a LOT!) has told the truth, and the truth is it just doesn't work. The boats are never the same and perform sub-par. It's just a really DUMB idea!

Bring on the haters! (but I do speak truth to stupid)

Chris......

 

[Mercperk]

Agreed, any new glass needs to be added to the old glass only after the old has had the surface 'broken'. You can't add new glass to gelcoat or old glass because of the wax that comes out of the glass...

An ali shim would act exactly as if it was a thicker inner transom plate. Nothing to worry about it getting loose... Take a sheet of 1/4" marine Ali plate and the inner transom plate to a laser cutter and have them cut it...

Chris.

And in the end moved the engine up

Boats designed for stern drives NEVER perform well with 'after-thought' outboard pods. I don't care how good the owners say they are, every single PREVIOUS owner of a podded outboard on a previously stern drive powered boat I've talked to (and there has been a LOT!) has told the truth, and the truth is it just doesn't work. The boats are never the same and perform sub-par. It's just a really DUMB idea!

Bring on the haters! (but I do speak truth to stupid)

Chris......

If you've got money to spend on throwaway motors more power to ya your probably not doing your own work

 

[achris]

Gotcha thanks. Yeah that wouldn't be ideal. Is it acceptable in any scenario to add layers to outside of the hull with gel removed first.? As yes the inside of transom left in the "rough" seems like I'd have to go pretty deep to start in there

That's probably the hardest of the options. Leaving the outside level and standard and building up the inside is way easier...

Personally, I'd go with the shim plate. Quickest, easiest and least invasive. Finish the plate with a black anodise and it'll last for ages. Add a layer of 5200 to the back of the plate so it sticks to the transom and you have a permanent solution.

Chris...

 

[Rick Stephens]

Yeah, one of the reasons that I stopped considering a couple 6s beyond all the other associated glasswork on a new doghouse. Those things sure are cheaper sometimes.

I thought Chris's suggestion was a single 383. Noting that you already are on the dual inline path, the big single would be killer.