Transom Reinforcement

Anyone know of a thread, or ideas for how to reinforce a transom on a 18 foot StarCraft?
.
I did a forum search but didn't find anything. I googled it and read some suggestions for adding more knee braces, but I just don't see where you'd attach more knee braces on the boat bottom of an aluminum StarCraft.
.
There's one big one in the middle and it appears it was installed where it won't create flexing at the bottom because of the curve of the bottom.
.
Would you guys worry about adding knee braces for a 300 pound motor for a 18 foot StarCraft?
I replaced the transom about 3 years ago.

With a solid transom, knee brace, splashwell, decking, and respective factory bracing which tends to vary from model to model, you shouldn't really need to add anything additional for a 300lb motor. Where problems tend to occur is when trying to run heavier/higher HP motors on compromised transoms. Soft transoms, cracked knee braces, cracked splashwell, rotted decking, missing/broken/loose rivets/screws...they all combine to allow flex and additional wear and tear that reduces the structural integrity both on the water and while trailering. That motor bouncing around on a compromised transom takes it's toll. The factory configuration did a pretty good job of engineering all the components to work together and add the structural stability.

One area that has been found to be a potential weak spot on the 18' and larger hulls is cracking at the ribs on those earlier models without the hull bracing. It was added on the later models (sometime early 80's maybe?) and seems to be more prevalent in those boats again that were pushed by higher HP motors with compromised transoms. There are several threads about this and great examples of the additional bracing being added. I know my '84 MR180 has the bracing from the factory.

I have a 90hp 2-stroke, so thanks, I feel better now.

I've had 2 45 year old 18' Starcrafts.
I ran 125hp and 115 hp Mercs on then.

AND had an 85# kicker hanging on the back.

No issues.

roscoe said:

I've had 2 45 year old 18' Starcrafts.
I ran 125hp and 115 hp Mercs on then.

AND had an 85# kicker hanging on the back.

No issues.

Click to expand...

I haven't gotten it out on the water yet, but I'm going from a 84 Suzuki 75hp 2-Stroke. The scupper holes at the bottom of the splashwell would ride right at the waterline with the Suzuki and my Yamaha 4-stroke 9.9 kicker.
.
I guess I'll see soon enough how much lower it sits in the water with my new to me Johnson 90hp V4. 2-Stroke.

I have a 115 Merc 4 cyl on my 18' SS and it weights in around 400 lbs. Although the V5 variant does have double knee braces with a very robust splashwell. The splashwell drain holes are still low like any other model with a 15" transom. Water does come in sometimes when launching on steep ramps but not any other time.

I also added a .100 thickness plate on the outside of the transom skin where a 1/2" piece of rotten plywood was before.