Oh man, that's a broad question. For starters if you are really bored and a nerd like me then you can read this, here is a link to a Catalina
355 manual. All the general info about maintenance should be the same.
Owner's Manual - Catalina 355 Owners
Are you planning on fresh or salt water
and was your speed boat on fresh or salt water
One regular engine maintenance item on the ocean and with an inboard that you wouldn't be used to is the exhaust
needing to be replaced every so often.
to tune the rigging on the mast
and inspecting connections is good to know. The mast
stays are replaceable maintenance items depending on age and condition.
Specifically on Catalina's per their manual (and I don't know if this is true for other boats and I also don't know how drastic it is on Catalina's) but they say after you tune the rigging you need to check the engine/drive shaft alignment.
Instead of bellows you will have a stuffing box. That boat specifically comes with a dripless stuffing box which is adjusted differently then a regular stuffing box.
You are probably already familiar with heat exchangers and zincs.
If your speed boat was not a cuddy or cabin
cruiser you will have to learn about your amp hour usage, charging
, how many battery
banks do you want and how do you want to use them.
another very useful site but gets more into the nitty gritty instead of general maint is
Welcome To MarineHowTo.com Photo Gallery by Compass Marine How To at pbase.com
it is run by a member
Sail. Very knowlegeable and as you run across new system or questions, check his site to see if he has covered it.