FORUM RULES UPDATED - The forum rules have been updated to continue to provide a friendly and safe environment for our member community. Please take a moment to review the updated rules and our terms of use and privacy policy. Click here for Forum Rules which has links to the 'terms of use' and 'privacy policy'.
The above link covers this topic pretty good. Weight was the issue, but there were successful duel engine Montauks.
When I had a Marlin, I went through the same thoughts. Weight and cost of up keep versus the cool factor. My Marlin was just a fifteen foot boat, but a number of owner had converted them to duellies.
in one of the notes, there is a link to a 1988 Montauk 17 that has twin 30 HP Yammies. He says he gets about 30 NM/H with 3 men aboard. That's about 35MPH. So, it can be done......YMMV