Re: I/O boats are loud
I've owned both I/O and outboards, I've had outboards that were ear piercing at high speed as well as an I/O boat that was down right loud. Most of the noise I heard from the I/O wasn't through the engine cover but exhaust noise at the water level. It was tolerable at cruise with the sound behind you, but it was loudest from behind the boat. I was driving a buddies boat, following him in my boat one day and was surprised at how loud it was.
On the other hand, I drove a new aluminum boat last fall with a brand new Yamaha 115 four stroke, and I couldn't hear the motor at all. The only way to tell it started was to watch the tach. If you weren't standing directly at the motor, you couldn't here it unless all else was really quiet, which wasn't the case that day on the river.
My 135hp Evinrude on my 18' aluminum boat is loud, but it's also a 30 year old motor. Its probably as loud as my old I/O, but at a higher pitch. With the motor running, you can hear nothing else. With the old I/O boat, you could at least communicate while underway, but not with the 135 hp outboard, it gets louder as you get going.
The solution if noise is the issue would be a newer outboard, whether it be a 4 stroke Yamaha, or Mercury, or an E-Tec. I think the E Tec is even quieter than the Yamaha, but I've not had the chance to run two side by side for comparison. I've also not driven a newer Merc either.
If I were to be buying a new motor, the choice here would be between the Yamaha and the E Tec in the 115 hp range. I think I'd lean a bit towards the E Tec but price would probably push me towards the Yamaha, and thought of not having to buy 2 stroke oil anymore would help that decision along too.
The best advice if your boat shopping is to go to as many boat shows as you can, sit in as many boats as you can, and drive as many as you can, then make your decision. Look for in water boat shows, you can't tell much about a boat with it sitting on a trailer in some convention center or parking lot.
Even if your not buying a new boat, having driven a new boat in top condition will go a long way in letting you know what to expect from a given boat or engine. Buying a new or newer boat can be a big expense, don't be afraid to ask questions and really look the boat over, inside and out.