Most folks have mixed results at best with them. Before you start adding things to the boat/motor make sure you have everything set up correctly to begin with. You have one of the most beloved motors of all time the 22 cu in 18-20 hp OMC motor. Pound-for-pound probabaly one of the best motors ever made. However, vintage OMC motors from this era have sort of an odd leg length. Prior to standardized lengths of approx 15" for "short shaft motors" and 20" for "long shaft motors" the leg was often and odd intermediate length around 18". Too long for be a modern "short" shaft, but too short to me be a modern "long shaft". Most samller boats have a 15" transom height which is fine for modern short shaft motors, but vintage motors tend to hang a little too deep in the water, which impairs performance and creates excess drag. I was in the same boat (so to speak), but it's pretty easy to fix. Ideally, you'd like the ant-vent plate found just above the prop to be level, or even up to 1-1/2" ABOVE the keel (bottom) of the boat. It may sound a little odd at first, but don't worry. All boats are stern heavy. As a result the LU will be sufficiently submerged at idle and low speed to pump plenty of water, while at speed on plane the anti-vent plate should just barely break the surface of the water thereby creating minimal drag and peak performance on the top end. You can buy/build a jackplate to raise the motor to the ideal height (plenty here in the forums to get inspired from), or you can do what I did which is to simply mount the motor as high on the transom as possible, while still being able to fully clamp it in place. The motor doesn't have to "rest" on the transom per se b/c it is the transom clamp that actually does the work. This should raise the motor about 1"-2". It's not quite ideal, but should get you much closer. Old school racers did/do use shims as small as 1/4" to raise/lower their motors to get the best seeds possible, so you might be surprised at what a difference raising the motor even a few inches will do. It certainly made a difference on my set up. You can then adjust the trim to get even better performance. I've found that the second position out from the transom is the best spot for my 14" semi-v tinny + '66 Johnson 20 hp combo. I'm able to get over 20 mph, which is good enough for me.