It's not a smart idea to make power boaters think your kayak is one of them either. They would expect you to be as fast and maneuverable as they are. Very dangerous. An all around white light is what you want on a non-powered kayak.
If your trailer came with 8" tires then it prolly has small axle hubs, and most are rated for a max tire size of 12". Just something else to keep in mind.
I had a similar issue recently with a 97' Merc 25. After replacing fuel line, bulb, and fuel filter in the engine, the problem persisted. I turned the tank upside down, opened the tank cap vent, and drained some gas into a clear jar. I had half gas and half water! I replaced the tank, and...
Here is what I built. It doesn't offer any set back, but did raise the motor to the correct height, which is 3" higher. My speed went from 29 down to 28mph, but I am running with 130# or so extra weight. I think I would have gained 2-3 mph, if not for the extra weight...
Here is my 42" mounted.
I also installed a quick disconnect outlet. I installed male ends on my motor and charger, so I just have to plug in the charger for onboard charging.
The motor riser works well. I was getting 29 mph before the mods. After raising the motor 3", so that the cavitation plate is even with the bottom of the hull, and adding 150# worth of decking, framing, trolling motor, and battery, I'm still getting 28 mph. I'm happy!
I also built a...
This bracket works great! My top speed before the bracket was 29 mph. With the motor raised up she runs 28 mph. I have added about 150# though, so I'm happy. She draws three inches less of water, which is the best gain.
I finished this one. I still need to paint all the aluminum to match the hull. I connected the same male plug on my battery charger, so that I can just plug it in to charge my deep cycle battery.
I removed the whole system, and am happy with it. I just can't give it much throttle in reverse, or she will kick up. I will try to figure it out and re-install parts some time in the future.
I replaced the bulb, fuel line, and filter. Same issues afterwards! I drained some fuel from the vent hole, while tank was upside down, into a mason jar. Lots of water in the tank! I bought a new tank, and now she runs like a new one!