No direct experience here, but a couple thoughts:

I was considering buying a used houseboat this spring and found most had
i/o drives. Most of those i/o drives had problems related to 1) age
(leaking seals) 2) corrosion.

Service required hauling and seemed overly expensive. On researching
the units, they appeared to be very complex, with at least 6 critical
seals. Aluminum was used extensively, and in sal****er that requires
very careful maintenance. All the units I saw showed problems with
corrosion. The design of all the units I saw did not allow the drive to
be tilted out of the water - tilt was only to provide reduced draft or
trailering and left at least part of the prop in lower unit in the water
at all times.

As I understand it, all driving force is transferred to the transom, and
this must be carefully engineered. (Ie. transom built like brick sh**house.)

I concluded that the i/o is a hot setup for quickie boats that live in
the driveway. I gained a whole new appreciation for the simplicity and
serviceability of a shaft and stuffing box, and set the houseboat idea
aside for more careful consideration later.

Rufus

André Langevin wrote:
I have a 34 feet houseboat with a Chrysler 318 driving a Paragon v-drive -
the problem is that no parts are available anymore for this tranny and i
would like to change it to somewhat more modern. I have two choices:

Stick with the propeller and shaft model and buy a Twin Disk or ZF v-drive
transmission

Get an I/O and install it on the boat.

Now i get very decent performance with my engine and propeller combination
right now. Low speed (8 kts) operation cost is about 12 $ an hour at 1500
rpm and high speed (18 kts) is about 40 $ an hour at 2700 rpm. Top speed
is 22 kts. I have no experience whatsoever in I/O and i would really
appreciate to receive comments on this.

Cheers

André