1989 4.3 Mercuriser alpha one prop?

[Justaboatin]

Hello,<br />I have a 1989 4.3 Mercuriser in a 18ft Sylvan bow rider. (1770 Lbs Dry weight) I have just purchased the boat. It came with a 19P aluminum prop. This is my first Ski boat (my others have been Jon boats)and I have a few questions.<br /><br />Is the only advantage to upgrading to Stainless Steel prop durability? or is there a noticeable performance upgrade?<br /><br />The boat jumps up and gets on plain very well, but tops out fairly quickly, is it underproped?<br /><br />(I don’t think the tach is working correctly, because at 3/4 throttle 35MPH I am showing 3500 RPM)????<br /><br />We are going to use the boat for cruising and pulling a tube. Any suggestions or thoughts?<br /><br />Thanks!<br />Scott

 

[Gary H NC]

Re: 1989 4.3 Mercuriser alpha one prop?

Scott,That motor should top out at about 4400 to 4600 rpm.<br />Some say stainless gives better performance and some say not..<br />WalleyeHead or one of the other prop pros should give you a better answer.<br />I'm running a 20 pitch stainless on my 4.3 but my boat weighs a bit more than yours.<br />I'm running about 42mph at wide open throttle but my rpms only gets about 4200.<br />I would get your tach checked then go from there.<br />What rpms are you turning at WOT?