Cant find factory diameter and pitch of prop!

[fordmxracer]

Trying to find factory diameter and pitch on a 1998 21' wellcraft excel ssx with a 5.7L v8 mercruiser. Any idea?

Thanks Ryan

 

[Silvertip]

Re: Cant find factory diameter and pitch of prop!

You can measure the diameter. On a three blade, measure blade tip to prop shaft center x2 = diameter. On a four blade, its blade tip to opposite blade tip. There is no such thing as "standard pitch" because the drive manufacturer has no idea what boat the drive will be installed in, what the power plant will be, or what the load will be. Check the prop itself -- there are usually markings on the barrel or behind the prop nut. The proper prop is one that allows the engine to operate in its recommended wide open throttle rpm with an average load. If you don't have a prop at all, start with a 21P and work with a prop shop that will allow you test props until you find the optimum set-up. Then be a sport and buy from them. If you have a prop but don't know the pitch, a prop shop can use a pitch block to determine that.

 

[walleyehed]

Re: Cant find factory diameter and pitch of prop!

We've got a slightly older model with the same engine and I believe silvertip is spot-on for the starting point. I've tested quite a few props on this rig and for all-out pulling/hole-shot, a 19P Lexor or Merc Mirage is Neck-breaking....for over-all best performance we've found a michigan wheel apollo in a 21P 3-bld to be a real good choice.

 

[fordmxracer]

Re: Cant find factory diameter and pitch of prop!

Anybody else with this same motor size run a 4 blade or a High five? Is 4 blade or even 5 blade needed. Boat is for the BEST whole shot. Primary function of boat is for wakeboarding!

 

[walleyehed]

Re: Cant find factory diameter and pitch of prop!

Then a good quality 4-bld will work quite well...The pitch required in a 4-bld will be 1-2" less pitch than the 3-bld that puts you at the top of your RPM range in most cases...There are situations where a 4-bld can increase the over-all lift enough that you may find the same pitch to work well..that may be tough to find if you're running an odd (typical) pitch.
If you could give us some numbers with what prop, I can give comparisons to most .....we really need those figures even to suggest, or give an honest guess at what you need for your application.