Better performance

[Travis]

I have a 1998 28' Caliber 1. The motor is a 454 mag and my prop a 3 blade mirage 21p. I am hitting 5k rpm at about 65 - 67mph. How can I get more top speed and bring down the rpm and not sacrifice to much bottom and mid range.

[Magic Sandbar]

Sorry to burst your bubble, but those numbers just dont add up. A 21 pitch prop at 5000 rpm will only push any boat, no mater what the hull or weight to 58.3 mph. The faster the speed, the less accurate the speedodometer. One thing you should consider is, if at 5k rpm do you still have more throttle? If not the next size prop (22" 4 blade) will only lug your motor down and give a slower time to plane. If at 5k rpm you still have a little more throttle, then a 22" 4 blade should help with overall performance and a little more top speed. A 22" at 5k will push a boat 61.1 mph, figuring 12% prop slip.

[StingRay]

If you're stock, and I guess you are with those numbers, try a K&N flame arrester which should spike up your RPM by a couple clicks (mine did on a 502mag) and depending on that blueprint, add xtra cup and maybe .5" of pitch to your blade once again depending on how the arrester affects the RPM. That's a cheap way.
Thanks to Kanookstr's help, I tried 4 blades etc. My original blade was a 25P Mirage+ and I got 5K on the tach. Arrester on, cup and .5" pitch later I was turning 5100 and the non-gps speedo jumped 4 mph! So I'm going to plug in the other .5" pitch for a full 26P Mirage+ and see if I gain more. The prop was already blueprinted by the way. Good luck..... http://free.***boat.net/ubb/cool.gif

[Travis]

To Magic Sandbar....Then how is the guy in the other Hot Boat Forum getting over 70mph out of his Advantage? Is it the 4 blade prop?

[Magic Sandbar]

I am assuming you are comparing apples with apples. A 22" 4 blade with 1.5:1 gearing, 12% prop slip and 5000 rpms will only move anything through the water at 61.1 mph. Maybe he has changed his gearing or is turning 5800 rpm to do 70 mph. Or he believes his speedodometer. Unless you are using radar or GPS your indicated speed using a stock spedo can be off as much as 15 mph or more at high speeds.