Prop selection for a 2002 Glastron SX 175 with a 3.0L Volvo Penta SX

[Swaff]

I'm in the market for a new prop, and I've read just about everything I can on propellers, but seeing as how I've never bought one before, I'm looking for a second opinion just to make sure I'm making the right decision.

I have a 2002 Glastron SX 175 with a 3.0L Volvo. My current prop is a Michigan Wheel Vortex 14.5x19 aluminum 3 blade. With that prop, WOT gets me to 39mph at 4800 RPM with just myself, a full tank, and usual equipment in the boat, and with it trimmed for speed. Lowest planing speed is about 20mph at 3000 RPM. I haven't tested extensively, but I haven't noticed this to change a whole lot with a few more people in the boat, which for me would be an average load.

I use the boat mainly for water skiing and tubing, and cruising at trolling speed or lowest planing speed. I really don't care about top speed.

Based on what I've read, I'm leaning towards a Michigan Wheel Vortex 14x20 four-blade aluminum prop.

My rationale for going with a Michigan Wheel Vortex is that I can reuse the hub kit from my current prop, and save some money.

I chose the four-blade to give me the best hole-shot for tow-sports, and to give me a lower planing speed, and therefore less engine noise, less wind noise, hopefully less fuel consumption, and more time to enjoy the scenery while cruising.

From what I've read, going to a four-blade should reduce my WOT RPM by 100. Going from a 19 to a 20 pitch should further reduce it by 200 landing at 4500 RPM, within the manufacturer's spec of 4200-4600. Of course, often I've got more people in the boat, and there's always the chance of more equipment being added, so at 4500 RPM empty, that still gives me some lee-way.

And finally, aluminum is cheap and easy to fix.

So that about sums up my thinking. As I said, I'm just looking for a second opinion to know I'm on the right track.

Thanks.

 

[jestor68]

The 19 pitch 4 blade is what you want.

 

[achris]

If you're using it for 'tow sports' then you need to go DOWN in pitch, or you'll be overloading the engine and risking damage. The general 'rule of thumb' for skiing/tubing is to go down at least 2" of pitch. You will probably end up needing more than one prop. For skiing/tubing use the smaller pitch, so the engine isn't overloaded, for fishing/cruising use the prop that gets you at about 4600prm at WOT.

Ok... that's what the book says. He's what 30+ years of experience says. Find out which prop gives you the best WOT (as close to the mid to top as you can, so for you around 4600-4800), then go one size DOWN. Less work for the engine, you'll find the boat far more 'driveable', actually quieter (because it's not having to work so hard) even though the engine is running a little quicker, and I know that sounds contradictory, but it works.Now for the ski/tubing prop, go one more down on what you're using for cruising...

So, if you're currently running a 19" 3 bld at 4800, use a 18" 4 bld as your cruising/fishing prop, and a 17" (or even 16") 4bld for skiing/tubing. And me, I'd stay away from Aluminium... Stick with SS.... As I have done for the last 13 years... (all the stories about SS props damaging drive internals are a load of bollocks! The only time I've broken a drive was when I hit a turtle, and that was with an ali prop. Sheared the drive shaft, not a mark on the prop (or the turtle thankfully). Since I've been using SS I've hit a few 'shallow objects', never broken anything...)

Chris....

 

[steelespike]

I agree w jestor a 19" 4 blade. AL prop.Your Michigan makes sense cost wise.
You may want to consider the Solas Amita and Rubex 4 blade. Solas uses "squeeze casting" this allows thinner stronger blades.
Forcing the motor to a lower rpm actually loads it more.
Marine engines work very hard.Picture a car pulling a trailer up a never ending hill; and you want it to do it in over drive.
There is no doubt that a ss prop "could" perform better but I don't know if it is triple the cost better.
If you boat where soft contact(mud and sand) is likely a ss prop should hold up better but may cost more when its time to repair.
Hard contact will surely cost more.
Buying al or ss props used is a bit of a gamble.

 

[adittam]

Hi all -

I have almost exactly the same setup as the OP, and am looking for almost the same exact results. 2003 Glastron SX-175 with 3.0L Volvo sterndrive, with a 14.5x19 Michigan Wheel 3-blade prop currently.

To expand a bit on his questions, what is everyone's real-world experience with 4-blade vs 3-blade props? I think I know what 4 blades are *supposed* to do, but is the difference noticeable in 17 foot runabout with a 3.0L stern drive? If I do decide to change to a 4-blade, is there a consensus size I should go with to get a little better hole-shot compared to my 3-blade 14.5x19?

Thanks for the help!

 

[steelespike]

Its really less confusing and your likely to get more specific help if you start your own thread.
The likely hood of anyone here having exactly the same setup is pretty slim.Other than the OP.
Your more likely to get better help with a new thread than tacked on to a 6 month old thread.
If you give us your performance numbers we can tell if your setup works.
Just based on your prop size I would suggest a 18" Solas 4 blade.
It us suggested to decrease one inch when going to a 4 blade.
Usually a 4 blade should improve hole shot,stay on plane easier,feel smoother
and may respond better around the dock.
By the way the best cruising speed could be from just on plane up to about 1000 rpm higher.

 

[adittam]

Thanks for the reply.

Frankly, I didn't want to start a new thread yet because I didn't have all of the necessary info regarding my performance numbers. My tach was inoperable last season (has been since I bought the boat in April 2014) and as a result I wasn't in a position to start playing with prop choice or push the boat at WOT last year. I've been working on troubleshooting my tach this spring and have a new gauge on its way to me now, so now I should be able to safely try a prop that's not stock specs this season. I also didn't want to disregard the feedback that was already given for the OP's setup since it is identical to mine.

 

[Slip Away]

The 14 x 20 4 blade Vortex is perfect choice for what you have. I have the same prop on our 20 ft. bowrider, and it is great.