Originally Posted by BUP

Alpha One back in that day Merc did have 454 engines matched up to them with a gear ratio of 1:32. In 1988 when the Bravo was introduced no more alpha's were used behind big blocks coming from Merc. I would stay with a 3 blade as it usually is a little bit easier on the drive compared to a 4 or 5 blade prop.

Your speed is way off or your speedometer is way off or the hub in your prop is slipping. Is this a recon prop - maybe pitch way off or bad rebuilt prop ?

Also is your boat carrying a lot of extra weight as another possibility - maybe water leaking in and or saturated foam / stringers - just saying as possible reasons why your speed is way off. Bottom of the hull very clean and in good shape also no anti fouling paint ?

IMO you need to try a new 23 pitch prop and possible check your RPM's to verify the tach is working correctly. Your boat should be a 50 mph at least. Your original drive ratio should have been 1:32 with an alpha matched to a 454 back in the 80's. I know SEI does not offer 1:32 gear ratio in any of the Alpha's..

How do you have a 1998 Motor matched to an alpha anyways ? Your Larson must be an 80's boat with a more current repower, is that correct ?