I've got a 19P Mercury High Five Stainless on my 180se with the 4.3 and love it. It leaps out of the water and planes out in 3-4 seconds. I'm sure the speedo if off, but I can still reach an indicated 47mph with three people and some equipment. It's rare I can go WOT at our lake (too windy) so this prop works perfect.

I checked with the prop shop and they did balance it, they are the most reputable shop in town so I figured they had. They offered to take a look at it again but at this point I am suspecting it may be the propshaft itself. If you hit something hard enough to take a 2" chunk out of the skeg and the hub did not break loose like it is supposed to it may have done some damage elsewhere. Ahh the joys of boat ownership!

Your speedo wont be off by too much. At best you could expect 48-49 mph with that 19p prop but theres no question that the High 5 is a nice prop, particularly for watersports.

So I replaced my damaged prop and upgraded to a 21p SS prop this time. The shop I spoke to recommended replacing the prop and taking it out again before bringing it in to see what is causing the vibrations. Good news is that the boat ran smooth, no vibrations so I am to assume the prop shaft is fine. Not sure if I liked the 21p prop though. The shop, which sells Cobalts and is a ceritified Merc dealer, said that if I am hitting 4700-4800 with a 19p prop I should leave it alone(should have listened). I was only getting 4200rpm with the 21p and did not notice any improvement in top end. I am going to exchange it for another 19p and see what kind of performance I get. The other thing that my shop said to keep in mind is that I will not get the same performance as someone else on this board with the exact same boat and motor combo who is in another part of the country or another country altogether. The lakes in AZ that I frequent are between 1700 and 2500 ft in elevation, which can have a big impact on performance. Not to mention they are always busy and very choppy, unless you go out at 8am the lakes are very rough. What elevation are you guys at?

Glad to hear it was just the prop and not the shaft causing problems. IF you were maxxing out at 47-4800 rpm with the 19 pitch prop then i would agree. 4400 - 4800 is the recommended range for the 4.3 so 4200-4300 rpm with the 21 pitch prop is too low. Where i boat in southern Ontario is around 500-600 ft above sea level. There is no question elevation negatively affects performance, particularly at WOT. Since air gets thinner as altitude increases, the engine begins to starve for air (oxygen) and horsepower is lost resulting in a noticable reduction in power & rpm. Usually a pitch drop of 2 - 4" will resolve that issue allowing the engine to rev into it's correct range. It sounds like a 19 pitch - 3blade SS prop or possibly a 19 or 20 pitch 4 blade will give you optimum performance in your location. Prop selection isn't a perfected science as yet despite all the tools out there. A lot of it is educated guesswork, experience and 'try it & see'. :)

What happened with your top speed? You indicated 40mph earlier. You should be in the mid to upper 40's i would think. Again, the best way to measure it is with a GPS unit.

My top speed with the new prop was in the low 40's, the lake was REALLY rough though due to holiday weekend traffic. This weekend when I take it out with the new 19p I will bring a GPS and see what I am getting. If the RPM's are back up to 4700-4800 I imagine I will hit between 48-50. I think if I was out at a lake with an levation of around 400-800 ft I could probably go with a 21 and still muscle 4500-4600 RPM out of it, problem is the only lake in az with that elevation is almost 4hrs away so I will stick with what works best in the local lakes.

My boat sounds about the same as yours, Shalayne. Big Red is 1997 Z210 with Alpha and 5.7LX. What pitch was your original prop and the High Five? I run a 21" pitch Vengeance, which is 3-blade stainless, and also a 20" pitch, 4-blade aluminum prop. Both props get me out of the hole adequately; the 4-blade comes out a little quicker. I was considering a High-Five 21 pitch, believing that a 19 pitch would take too much off the top end. I am also considering the smart tabs. They sound fabulous. Please let us know.