While I won't go so far as to say they are unreliable, as I lack enough experience with them for that, I will say that they are impractical, as I do have the experience for that. Basically, you are putting a car engine in a boat. You would have about the same issues as trying to power your pickup truck with a Johnson 250. The biggest thing is the bellows. It is the rubber boot that connects everything from the movable outdrive to the fixed engine. They get real brittle after a couple years - less even in hot climates. It is a pain in the tail to fix (involves disconnecting, and removing the outdrive), and it must be done about as frequently as a water pump impeller. Now, on an outboard, if the water pump impeller goes bad, and you marina store it, no problem, just get it fixed when you can and don't crank the motor. However, if the bellows goes bad, you better get the boat on the trailer, as water will pour through these, and sink your rig. boatus.com did a study, and 44 % of I/Os that sank at the dock were attributed to bellows or water jackets busting, and 20% that sank underway.
Also, look at the size of the hole in your transom, that must be sealed correctly, as well as all the other fittings.
This accounts for 23% of docked sinkings, and 24% of underway sinkings.
And, if you throw a rod, and it busts a water jacket, that could sink ya too.
Now, while those are uncommon, the only thing that boatus found about outboards sinking at the dock was bad cockpit design that trapped water, while that only accounted for 15% of the I/O dock sinkings.
Now, time to change the oil. Woops. No drain plug. Got to pump the oil out. Pain.
The weight too. I don't have time to look up the numbers right now, but I think it took a 135 I/O to equal a 90 outboard. 90 outboard - 375 pounds. 135 I/O (4 cyl mercruiser) - 700+
Figure out how to change a water pump too.
Now, lets get to servicing the engine itself. Nice hole sized so the engine and nothing else, which includes hand wrapped around wrench, would fit. Plus, it is dark, and you are upside down.
Also, your engine is trapped under your deck, so all your fumes must be ventilated, and a ventilation malfunction is much likelier to cause a problem. Plus, running the blower for 2 minutes before you start is not fun either.
If you marina store, especially in salt water, you cannot tilt your engine out of the water, so it is subject to whatever marine growth/salt corrosion the hull is, and keep in mind, it is made of aluminum, which will love to corrode in the presence of the electric field from shorepower. Same reason Marina stored aluminum boats need to be drystacked. One of the VERY short list of advantages to glass boats.
Now, the fact that you don't have an "ugly" motor on the back is a plus for some people, as is the advantage of a swim deck, on many pleasure boaters. But, once you get past that, and certain I/O jets for swift rivers, we have run out of pros. I kind of like the "ugly" motor on the back (unless it is a merc. :shock: )
Now, there are some other minor advantages to Inboard Outboards, but these can also be had with 4 stroke outboards, so it is pretty much nil.
