What's the correct prop

[karl1111]

I have repowered my 18' 89 Ranger 363V Bass Boat with a 2118 F150 Yamaha O/B, engine came with a 14.8X17 Aluminum Prop. I want to go to a SS prop and need advise on correct pitch. Currently I get a great hole shot but only getting top speed of 45mph at 5800 rpm, any higher rpm loses speed. Old 150 Evenrude (89) was getting 56mph at 5500 rpm with a lees than desirable hole shot. I've been told 2 different things - 1. stay the same just go SS. (lees flex at top end give more speed) and 2. go to higher pitch 19 - 21 (more pitch more speed). Nobody seems to know which would give better hole shot. Dealer turned out to be a bit of an a/hole so don't want to go to him.

 

[briangcc]

Have you run your specs through Yamaha's prop selector?

http://www.yamahapropselector.com/propSelector/web/

Should get you in the ball park.

 

[karl1111]

Have checked it out. When I input my current info and add pitch & dia. get no matches??

 

[wahlejim]

What was your diameter and pitch on the old prop? Gear ratio of the old 'rude?

You are literally at a 0% slip with your numbers. Something is wrong here. Going Stainless will not get you 10mph. Re-check your numbers with a GPS or shop tach

 

[karl1111]

Don't know what the gear ratio was on the Evenrude but I was running a13 1/4 X 27, 4 blade SS Shooter. Hole shot was bad but liked top end and handling.

 

[karl1111]

Sorry forgot to mention, have 2 GPS Units giving me same speed (within a mile or so). Also, ran along side another boat, same, same. My tach and speed are new Yamaha digital units installed by dealer with the engine.

 

[wahlejim]

All of the charts I am finding have the old Evinrude at 1.86. Puts your slip with that prop (that is a LOT of prop by the way), at 26%. These numbers are all over the place. The gear ratio change will affect your top speed to the slower side. Add to that the fact that you are already nearing the end of the 6000 WOT range for the Yamaha F150, you will be lucky to see 50 in the boat again, but it is doable with sacrificing hole shot and running WOT at the lower end of the RPM Range. (Your range is 5000-6000). If you can find a prop shop to let you try props, I would try a 19 and 21 pitch and see where the numbers get you, then you can decide if you want to go the stainless route. At best, Stainless might get you 2mph

 

[karl1111]

Thanks for the info. I know the 27" was to much pitch but the price was to good to pass up (free) and I banged up a 23 pretty bad so I kind of tweaked it back in shape and used it as an emergency get me home prop. Hard to find a shop that lets you try props out (but I'll do a little more looking), but if not, I think I'm going to take a shot and buy a 19".