I'm not seeing anything about the autopilot being removed from the helm of a houseboat. Just how to upgrade it and use it as well.
I tried in a test-save to reset and replace the helm to see if that would work to give the options to upgrade to autopilot. It didn't. What I found is Sim needs to have level 8 handiness skill for the upgrade option to show.
After making the upgrades (auto pilot and speedier engine) I was able to move the houseboat to a spot in the ocean, after it gave me the prompt.
It's my understanding that a Sim needs to be on the boat, near the helm of the boat to move the houseboat, initially. After it's set in motion click map view, left-click on the water near the destination and select Move Houseboat Here Using Autopilot.
When the houseboat is in motion, the Sim should be free to move around the boat as the boat goes to the chosen destination. To return to your home port, a Sim will need to be at the helm.
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To Reset/Replace the Helm:
Reset the helm using Nraas Debug Enabler:
Click on helm > Nraas > Debug Enabler > Options: Helm by Helm Street Designs > Object > Reset
By default the game won't allow to delete the helm. I deleted it via Debug Enabler.
Click on Helm > Nraas > Debug Enabler > Radius Purge 1
Replacing the Helm Object:
Via Buydebug > Misc Objects - filter content by Island Paradise (star w/arrow pointing up on the right of the screen.) The helm object is the first on the list.
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To Build a Houseboat off a Port (Basics):
You will first need to unlock the port you want to build off of. Note, this only allows you to unlock and edit the port, not the houseboat you'll be adding.
In Edit Town Mode:
1) Press CTRL + SHIFT + C to open the cheat console, type in "testingcheatsenabled true" without the quotation marks and press enter.
2) Press CTRL + SHIFT + C to open the cheat console again, type in "enablelotlocking true" without the quotation marks and press enter.
3) Enter Edit Town mode and click on one of the port lots in Isla Paradiso that you want to edit.
4) Click on the lock icon on the far right of the window that pops up.
5) Normal lot editing functions are now unlocked.
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To Add a Houseboat Platform:
1) While in Edit Town Mode and on the lot menu that pops up, click the dock button to select the houseboat size.
2) Now you'll have a Residential lot off the port. Click on it to start editing. You can use build/buy pretty much the same as a regular residential lot. Using the hand tool to grab the helm and mailbox to move them.
-- Don't forget to turn off the enablelotlocking cheat before or after starting to build on the lot.
Press CTRL + SHIFT + C to open the cheat console again, type in "enablelotlocking false" without the quotation marks and press enter.
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Reference Links:
SimGuruGraham's Guide to Houseboats in Game (FAQs on Houseboats)
https://www.carls-sims-4-guide.com/forum/index.php?topic=16602.msg316355#msg316355Problems on Houseboats
https://www.carls-sims-4-guide.com/forum/index.php?topic=16598.msg316298#msg316298Houseboat Autopilot
https://forums.thesims.com/en_us/discussion/771712/houseboat-autopilotReduce/Remove Lag caused by Houseboats
https://modthesims.info/d/665907