Transom strenght

[Richard Jackson]

Hi, I am replacing two Engines and stern legs and replacing them with a single larger engine and stern leg, obviously i have two holes in my transom and they need filling and a new one cutting in the middle. There will be about 60mm of existing transom and then the holes, the transom is 50mm of ply. The boat builder is going to fill the existing holes with ply and then cut the new hole, im worried that there will not be enough strength. the boat is 40ft and the Engine is going to be a Volvo penta 375. Any thoughts?

 

[jigngrub]

I personally would remove the old transom wood and install new with the one keyhole and no patches for the 2 existing holes.

It just wouldn't be worth it to me to do all of that engine and outdrive work and have a patched up transom that would have a higher likeliness of failing than a new stronger solid transom.

 

[gddavid]

How is the builder filling the existing holes? It sounds like the current plan is to plug each hole individually and not replace the entire plywood core. I would not be in favor of that approach and would prefer completely replacing the core material with a new continuous piece. The holes in the fiberglass need to be tapered back at a ratio of 12:1 where 12 is the distance of the taper and 1 is the thickness of the fiberglass. This page explains it much better: http://www.westsystem.com/ss/repairi...in-fiberglass/

 

[Ned L]

As gddavid said, a 12:1 scarf all the way around would be ok, However I doubt any yard will do that. Keep in mind that all the thrust and power required to move the boat through the water is transferred though the I/O lower unit to the transom, It is the gimbal bracket pushing on the transom that transfers this thrust. - The transom needs to be pretty solid.

 

[Woodonglass]

Uhmm I have to agree 3 keyholes in a transom on a 40 ft vessel is 2 to many!!! Plugs are just cosmetic, they won't add anything to the structure. Got any pics???

 

[GT1000000]

I agree with all of the above...
Don't spend your money on a half-a***** repair...
Irregardless of all the guarantees and warranties and promises that it will be perfect and so on and so forth...DON'T buy into it...
It is not their safety on the line...
Done right you will have ZERO worries, done wrong, well you had better have the CG on stand by...

 

[Richard Jackson]

This is the same boat as mine, not had a chance to take a pic of mine. so where that center strut is is where the new leg will go and the two holes filled and re glassed, just doesn't seem strong enough but what other options are there? i did say i thought he might cut away the transom to where the line that goes around the two engines and replace all that which is 50mm ply glassed, i think that would be stronger. cheers

 

[Richard Jackson]

http://www.customboatrepairs.com/jm...e-conversion-job&catid=2:repair-jobs&Itemid=4
just found this link

 

[Scott Danforth]

I myself would keep it a twin setup on a 40' boat. especially for low speed docking unless you are adding a bow thruster.

however its your boat. when downgrading from twins to a single, as everyone here has stated - the transom core needs to be replaced (not plugged)

 

[GT1000000]

The way I understood your original post...

The boat builder is going to fill the existing holes with ply and then cut the new hole, im worried that there will not be enough strength.

it sounded like the mechanic was going to just plug the two out drive holes and then cut a new hole in what was left of the transom, that would have left very little strength in the transom...
The way it was done in the link you posted, is the correct way to make this conversion...
Please, post pics of your conversion so we can follow along.
Best of luck and have fun!

 

[Ned L]

I would agree that the way it was done in the link is the correct way, and shows good quality work. (not quite what was described above).