Replacement prop 1992 Johnson 175 60 looper

wellcraftv20 · #1 07-07-2016, 07:03 AM

Was looking to get a new prop ordered today or tomorrow don't have time to mess around with trying 10 different set ups. Was looking at the Solas aluminum 4 blades for better overall performance and get up and go for my v20 and was wondering if anyone else has re-propped a 175hp, only seen 150's and 225's posted about. is 19inch too extreme? was thinking 17 would be perfect but just want to make sure I'm not burning up my motor by going to shallow with the pitch and revving too high at WOT. Specs point to 5000rpm. Thanks.

THEFERMANATOR · #2 07-07-2016, 02:43 PM

15 pitch IMO should be about right with a 4 blade. You're going to most likely lose some top end speed, gain some prop bite reducing slippage both of which will lower your WOT RPM's. With a 1.86:1 lower ratio, 5% prop slip at 5400 RPM's should put you right around 39-40 MPH for top end. A 17 at the same slip and speed would drop you back to 4750 which is near the bottom of your RPM band which would negate the 4 blade for better holeshot. Need to know your current performance numbers, RPM, speed, average load, current prop, diameter, pitch, and style to give you a semi accurate reccomendation though. And don't get hung up on pitch, some props bite REALLY good and will have no slip while others will have more. This isn't neccesarily bad, but you have to keep it in mind.

garbubba · #3 07-17-2016, 07:13 AM

One thing I rarely see mentioned here is cupping a prop. A good prop shop can put a cup or extra twist in the blade. Cupped props bite better imo, but more importantly it's like an in between pitch. Make a 19 pitch into a 2o, or a 15 to a 16. Good prop shops aren't common everywhere (where I live if it has to do with boats, we got it) but are worth the search.

The 19 pitch stainless prop on my boat had been cupped by the previous owner, I tried messing with props & quickly realized that the PO,(a navy seal) had been there & done that. A 19 would give me too high RPM's at wot & light, a 21 just couldn't get a loaded boat out of the hole. The cupped 19 fits just right.

THEFERMANATOR · #4 07-20-2016, 10:44 PM

Thats why I was trying to figure out what he has. Some props come with alot of cup while others don't have much. Some blades are flat with steady pitch across the blade while othets are progressive. There is SO MUCH MORE to propping other than just pitch and adding cup. Adding cup comes at a cost to top end in many cases. Yes it improves grip out of the hole and in rough water, but that drastic turn at trailing edge creates alot of drag. Then you have to take into account where the cup is added. Across the rear edge will decrease rpms at wot and help top end. Cup added around the ear acts like added rake and increases bow lift while also reducing wot rpm's and creates more drag. Theres alot to propping and setting one up.