Prop upgrade results Vengeance to Stiletto

[drivehard]

Couple seasons ago I upgraded my 305 with a 2bbl to a 355 with a 4 bbl. in my Bayliner 2050 Capri bowrider. With the new hp, I was able to over-rev my motor. I was running a 21" pitch Mercury Vengeance SS 3 blade. I upgraded to a 23" Stiletto. Here is the change I saw.

21" Vengeance
5000 rpm max WOT at about 52 mph

23" Stiletto
4400 rpm max WOT at 55 mph

Speeds are GPS verified.

I didn't expect such a drop on RPM. The new prop dropped me to the bottom of the suggested RPM band (4400 to 4600). I would love to try a 22" Stiletto...

Any thoughts?

 

[junior1113]

Re: Prop upgrade results Vengeance to Stiletto

stiletto 21 or 22 will be perfect

 

[MikDee]

Re: Prop upgrade results Vengeance to Stiletto

Wow! this is the 2nd instance of where I've seen a Stiletto drop more rpm then expected! but, pickup more speed! I am guessing it is because of the type of cup on the blade. Can you have the prop reworked for a little less pitch, it might be perfect then? Wait, throw some Mobil one synthetic oil in there, and richen your mixture screws to the max rpm, that should unleash more power, & give you some more rpm, on the cheap!

 

[Dhadley]

Re: Prop upgrade results Vengeance to Stiletto

Which model Stiletto did you get?

 

[n2ostroker]

Re: Prop upgrade results Vengeance to Stiletto

I would look to a 23p Laser II. The Vengeance is a 13.5" prop. Depending on the stiletto you got its either a 14 1/4" or a 14 1/2". The added diameter is what killed the rpms. The laser 2 is 13 3/4" which is better for a small block than the larger props. Or try the vengeance 23.

 

[drivehard]

Re: Prop upgrade results Vengeance to Stiletto

Thanks for the comments. I would like to try a 21 or 22 stiletto as well. Will a Volvo Penta prop fit on a Merc Alpha I? My buddy has a 21 Stiletto on a Volvo Penta...humm...

 

[Dhadley]

Re: Prop upgrade results Vengeance to Stiletto

Again, it depends on what model Stiletto you're talking about. If your buddys Stiletto is a new square bore prop then you can buy a hub kit and run it on your Merc. If he has a Volvo SX or Cobra SX with a pressed in rubber cushion then it's a different spline than your Merc.

A lot depends on which model Stiletto you bought and which model he has.