An old "blue book" indicates a 1956 model.
Although, the crankshaft is the same as the Mark 25, the crankcase and center main bearing assembly (reed block) are different. The center main bearing assembly probably must be changed out to see any improvement. The improved flow into the reed block is likely wasted if it cannot flow out as well.
Thanks JB I've used Peter's paint before, It is very good paint, but ,took so long to get it I was out of the mood to paint. May try local NAPA see if they can match it. Dave.
Your Wizard WM7A, 918214 is a 1957 Model & was the last in the series of Mercury built Wizards.. The serial # range is 917751-922750 for a total of 4999 motors built. Yes, he is right, just enlarging the front end will not do much good without opening up everthing from there back, leave it alone unless you do everything. The lower unit is similar to a KG7 but should not have a splined prop shaft & clutch disc's as a KG7, if it does it IS a KG7 lower unit, at least the foot. The Wizard had a smooth prop shaft with a shear pin as original.
If you're gonna try to match the paint, look for a protected spot where the original paint has not faded. Under the tank rim is a good place to look.
JW in Dixie