Looking at a 21 pitch merc cleaver prop. My boat has an alpha drive and a mild 350. Are these good only for surface drives or would I maybe gain some over my current 21 laser II?

It is PART # 48-89802 A5-21P

No, you won't gain anything. Your LaserII is a good choice for the alpha and 350. It was back in the day before the LaserII and Mirage ect. props, the submerged cleavers were used, because that was what there were available. If your rpms and speed are where they should be now and the prop has good bite. it is what it is. The Vensura 4 blade has on occasion shown to be faster than the LaserII, but not always. It will improve your mid range performance and hole shot. It's a bit of a personal fav of mine.

What are you looking to gain? Speed, midrange ect?

Looking to gain top end. I'm at 62-63 now and I'd like to get 65. I have some more tuning to do but it seems like I really have to over trim with the laser to get the rpm to gain any speed. Even with trimming high my slip is still around 12-14%. Would like to get it down to 10-12% but dont know if i can. I'm still trying to get my carb dialed in. It's close but not where it needs to be. I also need to pop my gear case cap and count teeth to see if I have a 1.47 or 1.50 drive. Just the difference in those ratios can throw slip off by 2% on the slip calc.

Dave,
Once you get the engine work completed and dialed is. The knowledge on the gear ratio as well, we can discuss the options. Lab Finishing is a way to gain 100-400 rpm and reap the speed benefits that follow.
Concords have a fast hull but have always had a CG that is slightly forward making trimming a little tough. When you complete the other issues, call us and we can help with the propeller dial in.

Brett

Thanks Brett!! Good to know I'm not crazy thinking this boat is hard to trim lol