Transom thickness question

[Kootenay Troller]

To my dismay I found my transom in my 1974 18 ft starcraft holiday delaminating and soft. Was pulling the motor anyways to figure out the knocking noise. It's a 140 merc with an MC1 leg.

Right now the transom is 1.5 inches plus whatever the thickness of aluminum is! Are there any issues with the outdrive and engine if I wanted to make a 2" or 2.25" transom? Or is the 1.5" the thickness it has to stay at for everything to work??

Thanks

 

[dozerII]

Re: Transom thickness question

To my dismay I found my transom in my 1974 18 ft starcraft holiday delaminating and soft. Was pulling the motor anyways to figure out the knocking noise. It's a 140 merc with an MC1 leg.

Right now the transom is 1.5 inches plus whatever the thickness of aluminum is! Are there any issues with the outdrive and engine if I wanted to make a 2" or 2.25" transom? Or is the 1.5" the thickness it has to stay at for everything to work??

Thanks

You should fine that there is 1.5"of transom ply with a 1/2" ply layer on the inside where the transom fixture is bolted. I believe the max thickness is 2 1/8 to 2 3/8"
Here is a photo of the finished transom in my 201.

 

[Kootenay Troller]

Re: Transom thickness question

The transom that is in there now is only 1.5" all the way through, It doesn't have the 1/2" buildup like you show in your picture!

I never ran the boat, just got it and started working on it. What kind of issues will not having the required transom thickness create?

 

[GA_Boater]

Re: Transom thickness question

The thin transom can cause coupler to fail, u-joints to fail and gimbal bearing to fail caused by insufficient clearance. Often noted by knocking noise when operating the boat. Transom should be flat and 2 - 2 1/4" for 8" around the cutout. Page 33 in Merc Bravo Installation PDF, but the same for all models. http://www.mercurymarine.com/media/mercury/drawings/bravo.pdf

 

[Kootenay Troller]

Re: Transom thickness question

I am pulling the engine due to a knocking noise that I think is a connecting rod, in addition I could also hear a faint knock from outside of the boat by the leg. I just thought it was engine noise being transferred through the hard parts

What kind of knocking noise would this thin transom cause?

Not sure if its factory or if its been replaced but its all painted white and the top edge was poorly siliconed and it looks like the gunwale end pieces have been bent up and massaged back down so I'm gonna say its been replaced before!

 

[GA_Boater]

Re: Transom thickness question

Knocking as you turn and sometimes trim.

 

[barato2]

Re: Transom thickness question

Kootenay....go to NAPA and get a mechanic's stethoscope. under $7 and will let you pinpoint the source of any noise.

 

[bob johnson]

Re: Transom thickness question

I think the gist of the question is ...is there any relationship between the outdrive mounting and the inside plate that is critical?? is there anything connected that needs a fixed amount of space???? I think the bolts might not be sufficient.....for one.....the shifting arm seems to be mounting on the inside plate, but runs out to the outdrive connection....is there a 1.5 " flexible mount???? I have only taken one apart....and it SEEMS that there is a relationship between the two pieces ( outdrive and inside plate)good luck.........bob