Transom Thickness on a Sea Sprite tri-hull

[slimdaddy45]

I need to replace the transom in my boat it has a 1'' wood core but I read that everybody puts 1 1/2 '' in should I do this or leave it at 1'' which would be close to 1 1/.2 with the outer & inner skin its on a Seas Sprite tri-hull if I go thicker not sure if the cap will fit the way the splashwell is made so is 1'' enough since it came from the factory that way it has an 85 hp motor .I will be using marine grade plywood 5ply which would make it 10 ply . the splashwell drain was broke and it only has rot in the center of the transom

 

[ondarvr]

Well, did the transom fail from being too weak over the decades of use since new? If not don't reinvent it.

 

[slimdaddy45]

No I guess it didnt just from where the water got in from the splashwell drain the tube was broke the sides was still good wood but where the motor sits is bowed out some so I want to replace it now before it rots more and cracks the fiberglass

 

[slimdaddy45]

Nice looking old boat for a 74 model

 

[gm280]

I have to say I am surprised it is only 1" thick transom. Especially with an 85 HP engine mounted on it. What does the capacity plate state as maximum HP?

 

[slimdaddy45]

I have to say I am surprised it is only 1" thick transom. Especially with an 85 HP engine mounted on it. What does the capacity plate state as maximum HP?

Its rated for 85 hp

 

[Woodonglass]

Post some pics of your transom measurements. Where are you taking this measurement?

 

[slimdaddy45]

Post some pics of your transom measurements. Where are you taking this measurement?

That was the wood itself 1'' of wood plus the outer & inner skin . I measured it at the top just off the middle about 4'' from where the motor sits where the wood was good I have it tore out now so all together probably 1 1/2'' dont know what kind of wood was in it but it was tuff where it was good wood and was a red cedar colored wood never seen plywood that color before. I can get a pic since I dont have it all ground out yet you can see the bottom where the inner skin was tabbed in

 

[ondarvr]

Make sure everything will fit back together if you go with 1.5" ply. 2" became the default thickness for transoms from 40HP to 300hp, they don't all require that dimension though, and depending on how the splash well is designed a 1" transom could be far stronger than 2" transom. So don't panic or think it needs to be made stronger, 85hp is at the lower end of the HP ratings now. As I said before, if it didn't fail over all the years it's been in service there isn't any reason to think its undersized for this application.

 

[Woodonglass]

If both the inner and outer skins are 1/4" thick then a 1" wood core would be more than ample support for a 85hp motor. The Fiberglass, at that thickness, is very strong. IMHO this would be a GREAT candidate for a SeaCast Poured Transom. Have you cut the inner skin out?

 

[slimdaddy45]

If both the inner and outer skins are 1/4" thick then a 1" wood core would be more than ample support for a 85hp motor. The Fiberglass, at that thickness, is very strong. IMHO this would be a GREAT candidate for a SeaCast Poured Transom. Have you cut the inner skin out?

Yes I have it was bad delaminated so I cut it out

 

[slimdaddy45]

[No message]

 

[jbcurt00]

Not sure where that link ^^^ was supposed to go, but its a dead link.

 

[Woodonglass]

Yes I have it was bad delaminated so I cut it out

That's to bad. Like I said. With it being that thick and the outside skin being so thick you could have chain sawed out the wood and poured in a seacast composite transom.

 

[slimdaddy45]

I cant seem to load the pics says there to big but went out and measured again 1'' it is and the top cap the lip is 1 1/4'' so 1'' of wood and the 1/4'' of glass [outside skin] is all that it will cover may put like 3 layers of 1708 on the front and mark out where the splashwell fits and keep it where it will still fit and build up below it .So I will do as it is 1'' of wood so I will use a good marine plywood Menards has it in stock 49.99 a sheet Transom size it 63'' w X 20'' where motor is can anyone give me a guess on how much resin Ill need gonna use poly with csm 1.5 oz and 1708 and also shouldnt the stringers be hooked to the transom mine is not they end about 4'' from the transom should I glass a piece of wood in there to connect them

 

[Woodonglass]

Stringers aren't always attached to the transom but...It won't hurt anything if you do. It will make it stronger for sure. This might help... View attachment MaterialsList.pdf

 

[slimdaddy45]

Stringers aren't always attached to the transom but...It won't hurt anything if you do. It will make it stronger for sure. This might help...

Thank you