To put it simply, most off the shelf mounts are to weak to hold a gas engine. Electric uses thrust not prop torque to move the craft. This is why a flimsy rod holder mount that works on electric setups, will get destroyed with gas power.
Personally I have built very simple mounts using crates, bought rod holder mounts numerous times, and finally did enough research and spending of money to realize that companies do exsist that have a bigger R&D budget and their mounts actually do what they say and get results. Railblaza is the first easy on and off mount purchased that is store bought and works. Superior materials and proper coatings on the metal allows this mount, found below, to stand up over time and can mount up to a 2.5 hp gas engine safely. The mystery was finally solved.
Once mounted, offset weight or engine side flotation is needed to balance the 23lbs.
If store bought is not the answer, then keep on reading. Each mounting system needs to be thought out completely before you take on the task. From mounting positions, rudder usage, float type and height, to creating something that is effective and portable, all need to be thought out in advance. I have built over 6 different versions of mounts that are solid and perform, but every boat design is different and some have been an expensive epic fail.
Example Side Mount on a Vibe Sea Ghost
There are some video clips at the bottom of the page of a very inexpensive crate mount to give you an idea on how simple the side mount was to build, use, and how it performed. This just composed of a milk crate, 2 x 4, 4 turnbuckles to lock the crate to the kayak, S hooks, 3/4 PVC pipe, 2 large crab floats from Amazon and stainless fittings. Kayaks will vary on performance and hull speed, but it will certainly get you to your favorite spot. I added a longer mount and had to adjust the vertical height of the engine to get optimal speed and performance. Once the example was made, the next step would have been to make it out of aluminum and stainless with even more adjustibility for vertical positioning for a multitude of fitments. But for now, this is inexpensive and works perfectly. Take a look on this page to see some of the close ups of the fittings and turnbuckles.