StarCraft 181 SS conversion

[Shawnspeed]

I recently acquired a 181ss that has the out drive and motor removed for rebuild , and previous owners found a cracked block… it’s also an OMC120… not the most desirable powetrain.. the Transom is also out for replacement, so my plan is to fabricate an aluminum tube transom, plug the stearn drive holes and convert to an outboard. No offshore bracket, mounting to transom..will be adding internal gusset to help stiffen transom, and add a splash apron. I am somewhat new to boats , but not fabrication ( 30 years fabbing bike and car parts.. professionally) , just looking for tips or pointers from those who might have done something similar… Thanks!

 

[redneck joe]

Welcome to the forum. Sounds fun.

I'm not help but several here have done conversions and they will drop in and help

 

[Fj40fiji]

I’ll be watching!
I built a 2”x3” box tube transom for a 14’ welded boat. It was not terribly difficult but probably not worth the effort. I probably would have been better off with a single piece of tube across the top of the transom and then wood from there down. You really have to plan your penetrations, tie down eyes, swim platform etc. because water can get into the tubing and wreak havoc for a while without noticing, and compared to a wood transom it really limits where things can go to be supported on tube. I reinforced inside the tubing where the motor clamped on and sleeved where I was putting bolts that would see higher loads, but it would have been a big project to add or change anything later.

 

[Shawnspeed]

I’ll be watching!
I built a 2”x3” box tube transom for a 14’ welded boat. It was not terribly difficult but probably not worth the effort. I probably would have been better off with a single piece of tube across the top of the transom and then wood from there down. You really have to plan your penetrations, tie down eyes, swim platform etc. because water can get into the tubing and wreak havoc for a while without noticing, and compared to a wood transom it really limits where things can go to be supported on tube. I reinforced inside the tubing where the motor clamped on and sleeved where I was putting bolts that would see higher loads, but it would have been a big project to add or change anything later.

I am planning on sleeving the motor mount holes, as well as the tie down eyes..may also just add some 1/2” plate in the mounting areas, as I have some available.. thanks!

 

[Shawnspeed]

So , it’s been a minute… and I’ve abandoned the Tube Transom, and went back to a marine grade plywood transom, the added cost of the tube didn’t balance out , even over time.. I could put 3-4 plywood transom in for one aluminum one .... so I am about to begin splash well construction, and transom gusset fab, and I was pondering how deep, ( forward from the transom) a splash well is?? I currently have the top bulkhead from the inboard installed and I would like to keep that location, but it looks a little short at 20” … anyone out there with a 180 SS care to throw a tape measure on there splash well?? Thanks!

 

[redneck joe]

I have an 18 mariner i can get info for you if no one else with an SS does.

 

[airshot]

So , it’s been a minute… and I’ve abandoned the Tube Transom, and went back to a marine grade plywood transom, the added cost of the tube didn’t balance out , even over time.. I could put 3-4 plywood transom in for one aluminum one .... so I am about to begin splash well construction, and transom gusset fab, and I was pondering how deep, ( forward from the transom) a splash well is?? I currently have the top bulkhead from the inboard installed and I would like to keep that location, but it looks a little short at 20” … anyone out there with a 180 SS care to throw a tape measure on there splash well?? Thanks!

If properly done, the plywood transom would outlive you ! My 1983 Islanders transom lasted for almost 40 years and back then nothing was treated, just plain marine grade plywood. What are the chances of you still owning that boat in 40 years ? Definitely not worth the cost of aluminum.

 

[rolmops]

It depends on the engine that you hang on there. By this, I mean how far forward the engine comes over the transom when it is down and how far it comes in when tilted upward. Some engines sit farther back on the transom clamp than others. The farther forward, the deeper the splash apron and the lower the transom height, the more of a chance you stand of water coming in when you have incoming waves or when backing up. Getting an outboard with an extra long shaft (25 inch) that is probably the smartest. Also, when you use plywood, you will need it to be 11/2 inches thick , made of very dense plywood (marine grade) that you will have to seal against water intrusion.

 

[Shawnspeed]

It depends on the engine that you hang on there. By this, I mean how far forward the engine comes over the transom when it is down and how far it comes in when tilted upward. Some engines sit farther back on the transom clamp than others. The farther forward, the deeper the splash apron and the lower the transom height, the more of a chance you stand of water coming in when you have incoming waves or when backing up. Getting an outboard with an extra long shaft (25 inch) that is probably the smartest. Also, when you use plywood, you will need it to be 11/2 inches thick , made of very dense plywood (marine grade) that you will have to seal against water intrusion.

I bought 3/4 marine plywood, and laminated 2 pieces together and sealed with polyester resin… and the splash well depth/length must be some standard number… I can’t see boat manufacturers making different splash wells based on the customers engine choice.. just doesn’t make sense to me…

 

[roscoe]

If I remember correctly, the splash well on my 18SS and my 70's mariner, was 34" front to transom.

I then bought a newer Mariner ('82) and it had the smaller 11" splash well.
So I gained 23" of boat interior space, but still had the same length boat.

You can make the well as deep or long as you like, as long as your outboard doesn't hit, when fully tilted up, and it is high/deep enough to catch/deflect any wave come over the transom.

I am cautiously aware of any following seas with the tiny 11" splash well.