Which 4 blade prop should I get?

goody263

Cadet
Joined
Aug 13, 2013
Messages
10
I have a 2005 four winns 170 horizon fish and ski runabout that I've only owned for about a month. After considering trim tabs and having difficulty with the placement on this boat, I've decided to try a 4 blade prop to decrease my planing speed and increase the low end for water sports.

I did a test this weekend, and hit WOT with my current prop (21" pitch, I believe a quicksilver prop, 3 blade) at just over 4600 RPM, which is at the top-end for my Volvo Penta 4.3GL V6 with SX drive. I had three adults on board, so I figure the passenger load was pretty average for my boat. It is possible, that if I'd had more room on the lake to stay at WOT for a bit longer, the boat may have approached 4650+ rpms, but I was running out of real-estate, so throttled down.

Now, after some research, it seems that my current 3 blade prop is correct for my boat, and that would likely dictate a 20" pitch 4-blade. I don't want to jump to a stainless prop at this time, due to cost, and thus my options are fairly limited. I've narrowed my selection down to these three props:

-Quicksilver Diamond 4 20" pitch, model QA2186X - this seems like an obvious fit, albeit the most costly of the three by about $40
-Solas Rubex 4 19" pitch, model 9513-143-19 - this seems like it might be moving down too far, possibly, though I almost never have a desire or need to go WOT, and thus would not likely have a need to exceed my 4600rpm high limit.
-Solas Rubex 4 21" pitch, model 9513-140-21 - this might be moving up too far, and might impede performance at the low end, though if it only changes my WOT rpms by 100 or so, I'd still be at 4500+ with WOT, which seems clearly within my 4200-4600 range.

I've seen positive feedback about the Solas Rubex 4 props, and a friend has stated that the quicksilver diamond 4 is a good prop, so I'm really on the fence. Does anyone care to shed more light on this subject? Thanks in advance.
 

goody263

Cadet
Joined
Aug 13, 2013
Messages
10
Re: Which 4 blade prop should I get?

Okay, after re-reading this site's propeller tips page, I noticed it says that my WOT rpm should be near the midpoint of my rpm range, which for my boat would be 4400. I think, therefore, that that would give the edge to the last prop, the Solas Rubex 4 21" pitch, as that would likely reduce my WOT rpms so that they're within the range, rather than near the max. Is my reasoning sound?

Also, I didn't get a GPS based speed at WOT, but it was approaching 50mph on the boat speedo, probably around 48mph.
 

MBAKER

Petty Officer 1st Class
Joined
Jun 9, 2008
Messages
285
Re: Which 4 blade prop should I get?

just FYI...I just tried swapping from a 3 blade powertech 19P prop turning 4900 to the exact same solas 19P 4 blade you are looking at and it pulled my engine down 600 rpms. I was only expeciting a coupel hundred. I havent gotten any feedback yet if that is typical or how the Solas blade compares to an aluminum Powertech, Michigan, Mrecury etc. I have a thread on the topic started, you might find some useful info in there eventually.
 

goody263

Cadet
Joined
Aug 13, 2013
Messages
10
Re: Which 4 blade prop should I get?

The 21P 3 blade that is on it now is an OEM Volvo Penta aluminum prop, 14.3" diameter.
 

Barnicalpete

Cadet
Joined
Aug 14, 2013
Messages
6
Re: Which 4 blade prop should I get?

If you goin to invest in a four blade prop its really worth the little more for stainless, powertech make a huge selection of four blades with each being designed for a certain purpose, the rxb4 is a prop designed for acceleration and will give you the pull your looking for for skis, we used this on our recovery bOat and use it for towing alot. Its a superb prop plenty of bite and a great ride quality. Hope this helps, just my two cents worth 😁 happy 🚤
 

ronboonville

Petty Officer 1st Class
Joined
Jun 6, 2012
Messages
287
Re: Which 4 blade prop should I get?

When I needed a new prop and wanted a 4 blade to pull tubes better I went with what I-boats recommended and have been pleased.
 

fishrdan

Admiral
Joined
Jan 25, 2008
Messages
6,989
Re: Which 4 blade prop should I get?

With those numbers, I would go with the Quicksilver 20 pitch. Rule of thumb is to drop an inch of pitch when going from a 3 blade to a 4 blade prop...

Your doing great turning at the top end of your engine's WOT RPM range and I wouldn't look to lower it to get into the mid range. The Solas 19P would most likely overshoot the WOT RPM and the 21P Solas would probably pull the RPM's down too much.

BTW, I'm running an Alpha4 prop (same thing as the Quicksilver Diamond with different paint) and I love the prop, great match for my boat. Huge difference in performance over the 19P 3 blade I was running.
 

bunker108

Chief Petty Officer
Joined
Jun 26, 2011
Messages
482
Re: Which 4 blade prop should I get?

I also have an 18' with a 4.3GL that came with 21p 3 blade aluminum. It did fine but was sluggish out of the hole fully loaded at a 4000' lake. I dropped down to a 19p Solas 4 blade. I can over rev it light but it is perfect when loaded. This is my everyday prop and I use the 21 as my spare, or light loaded prop. You just have to decide what type of prop you want for the kind of boating you do.

I have been happy with the 4 blade Solas but plan on upgrading to a 4 blade SS which I think will be the perfect compromise for an all around prop.
 
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