When i am at full speed the bow of my boat comes up a bit and the water line is very close to drowning my motor that is mounted in the transom motor well on my cat 27. I want to find out if by adding a foil if it will prevent my motor from digging deeper in the water and keep it level more?
Firstly it's not clear that you understand the concepts of displacement hulls, and hull speed.
Most sailboats have what are called displacement hulls, which are optimised for a mode where the water passes around the boat, instead of the boat riding over it like the planing hull of a speedboat. This means that your sailboat does not have the hull features which would make it plane - at ANY power (those features are large flat sections aft)
So you are stuck in displacement mode. A displacement hull has a concept called hull speed. This is the point where you are putting in more and more power, and not going faster. The power goes into the bow wave which gets bigger and bigger. As the bow wave gets bigger, the bow rises up it and the stern drops. This is your problem.
The fix is to go more slowly. I cruise at the point where the exhaust pipe is just above the water - about 6 kts on my boat.
I would expect your C27 to have a hull speed of about 6 kts, though you might get too much squat lower - as low as 5 kts.
You will also get much better fuel consumption cruising at the speed where the squat is small, as the power is going into moving the boat, not creating a huge bow wave.
The trim of the outboard is one place to look, as mentioned above.. If by 'foil' you mean those fins they add to outboard cavitation plates, that might be worth investigating, but I'd be skeptical.
You may be powering on too hard (and likely not gaining any speed anyhow) so throttle back to reduce the 'squat' and see if things go better then. But also check the trim pin on the clamp bracket.. if the motor is tilted up aft, that will promote the 'squat' that's giving you problems. Try going to the lowest pin setting there.
not the only one with the issue. outboard powered sailboats have limitations on the conditions that it is safe to operate in. so far has the engine you have been a problem or is it that you are just worried about a problem that does not exist. if you find that going at top speed is drowning your motor then don't go that fast. problem solved.
I'd experiment with the throttle and the knotmeter... back off until the 'squat' eases up some, and see if you really lose any significant speed. Displacement hulls pushed to that squat position often don't gain any real speed... they just burn more fuel and make bigger waves.