In the dozen or so tin's (and one 'glass) boat, I've found one use for a hydrofoil. On the glass boat, the transom was junk and I wasn't spending the money to fix it, so I attached some thick aluminum to it and mounted the motor. Just used the Aluminum as a "stiffener". The weight of the aluminum + 3 batteries + all my junk in the storage boxes in the aft of the hull put the motor DEEP at low speeds, such that a holeshot was next to impossible. It would stand the bow up so high that I could not see over it, period, and if the GF was with me, it wouldn't even break over onto plane. Once I had her run forward and once it broke over, it was good to go...48 mph...so I put a hydrofoil on it. The problem SOLVED, but it also lost 3 mph. Raised engine one more hole on the transom and got my MPH back but it also affected the holeshot every so slightly.
If you're blowing out, the prop's getting air (or exhaust) to it. That can be caused from a lot of things, USUALLY from a hull that's causing a lot of turbulence, a bad prop, perhaps a spun hub? Is there any sort of a transducer mounted within 12" of the prop? Especially directly in front of the prop. How about a livewell drain? I have seen a pair of drains cause some turbulence too...get on plane, worked fine for a little while, and as soon as they was drained, it was pulling air into the water stream causing some ventilation. They were directly in front of the prop, exiting the transom just below the 2 intakes (one for each well). Have you tried a different prop yet? If the hull's got a bunch of imperfections near the edge, it'll not help matters any. Ideally you want a smooth transition between bottom and transom, with few (or no) dings, big dents, etc. in the last 3 feet of hull. I had one that was hooked (big dent from the bottom up) about 3", and roughly a foot in front of the transom and it would also blow out easily. Sometimes a LITTLE hook is beneficial but you have to put a LITTLE in at a time. Rocker (bent from the top downward) will cause issues too but not usually ventilation/blowout.
The pin is adjustable. Just like a "small" outboard. That's what it's there for. If you find that one hole is too far "in" (plowing water with the bow), and the next hole is too far "out" (blowout or porpoising), you can get yourself a metal sleeve that fits over the pin; which is what I do. That can get you "in between"...yes mine blows out in turns too...completely normal. I also do not have power trim (or tilt for that matter).
A 4 blade prop is less likely to "blow out"-and is more tolerant to turbulent water, higher mounting heights, they run smoother and get out of the hole better....BUT...lose a mph or two (usually). A bent or dinged prop is MORE likely to blow out. Have run into that with a 15HP yamaha, guy who owned it said he'd tried everything he knew of, and I suspected prop right off the bat...gave him a spare I had laying around and said here try this. Called me about an hour later and said his prop looked fine but he tried it anyway, and picked up 6 MPH, came out of the hole better, etc. He was right, his old one "looked" perfect visibly. But it wasn't obviously.
I "Think" that a two stage PT&T unit from a later model 50hp will fit your motor; and I think that'll give you trim. But you'll have to research which years will work as I do not know. I replaced one on a 50 earlier this year and it had trim...looked identical to yours. A lot of those motors (especially the C40's) didn't have trim...Tilt only. You may also find a bolt-on PT&T from a different 40hp...maybe a P40? It'd be worth researching. Some of these PT&T units show up on ebay and not real expensive, either, in some cases. Wish I could get one to fit my 25 (but won't...clamp bracket is completely different and to my knowledge, the long shaft bracket won't work on a short shaft motor).
