Let’s talk props

[Off in the Bushes]

So what’s the deal with 5 blade props?
I currently run an 3 blade and when water skiing it is all the boat can do to get a 200lbs skier out of the water. Boat has a inboard 6 cylinder 3.? L engine. Was looking at a 5 blade for more torque? But reviews say reverse does work well with a 5 blade. Is a 4 blade a good compromise?

[Yukongold]

You don't need spend a bundle on props. 3 blades is all you need. Drop the pitch when water skiing . What pitch are you using now? You need a 13P or possibly a 15P depending on what kind of power you are running. 4 bladed props can give you a decent hole shot depending on the pitch. They grab the water good and will plane the boat at a lower speed but will be slower at crusing RPM. Light loads and speed go higher pitch. Heavy loads (water skiing) drop the pitch. Props are easy to change so don't be afraid to switch them back and forth.

[elkhunter11]

Typically four blade props improved holeshot, stayed hooked up better when turning, but reduced top speed, but some recent designs, improve holeshot, stay hooked up much better, and do it without reducing top speed at all. It all depends what is available , for your application.

[Curly Bill]

What about reverse? I heard 4 and 5 blade props don't grab in reverse well.

[IL Bar]

I put a stainless 3 blade 14.25x17 pitch prop in my boat with the 3.0 Volvo penta and it made a completely different boat out of it. Really pulls hard now. I had a 14.5x19 aluminum in it before.

[DiabeticKripple]

A stainless 5 blade is great for pulling. Just watch for rocks as you won’t break the prop, you’ll break the gearing inside the leg.

[elkhunter11]

It may not apply to the OP, but if you order a Lund boat with the 75/90/115 Mercury , at least some are shipped with a four blade aluminum Spitfire prop. And the performance upgrade recommended by Mercury, is the Spitfire X7, which is a stainless four blade prop. If the reverse was a major issue, I doubt that these boats would come with a four blade prop. I will get to test this for myself next spring, when my boat arrives.

[Off in the Bushes]

So is the pitch and size stamped on the prop?
Is there a performance difference between aluminum and stainless?

[SamSteele]

So is the pitch and size stamped on the prop?
Is there a performance difference between aluminum and stainless?

Yes, the pitch and size should be stamped on the barrel of the prop, or sometimes inside by the hub.

Big difference in the performance between SS and AL props. AL props will flex under load, changing their pitch and the performance. SS remains rigid and won't flex at all.

As noted though, this works against you if you hit rocks as the SS will not absorb the force as well as the aluminum which would likely just break off a blade or two. The SS props generally have hubs that are designed to spin before damage is transmitted to the gearcase, but they may not absorb all of it.

WRT 4 blade props and reverse, I have noticed a slight difference but realistically I am not running reverse for more than unloading the boat or pulling away from the dock. If you back troll that would be more of a concern.

[Buckhead]

It may not apply to the OP, but if you order a Lund boat with the 75/90/115 Mercury , at least some are shipped with a four blade aluminum Spitfire prop. And the performance upgrade recommended by Mercury, is the Spitfire X7, which is a stainless four blade prop. If the reverse was a major issue, I doubt that these boats would come with a four blade prop. I will get to test this for myself next spring, when my boat arrives.

The aluminum Spitfires are not very good. Went thru 3 of them in as many seasons. They might be OK on pontoons or that sort of craft.
The Spitfire X7, however, is a completely different animal. Gets on plane well and can be tuned for more holeshot if you like. Holds in the corners and has an excellent midrange - which is what I like. Loses about 2-4 mph over a 3 blade in top speed but since I run a lot of rougher water that is a nonissue.
I haven't any issues using it in reverse. Backtrolls fine as well but I wouldn't normally use it for that.

[elkhunter11]

The aluminum Spitfires are not very good. Went thru 3 of them in as many seasons. They might be OK on pontoons or that sort of craft.
The Spitfire X7, however, is a completely different animal. Gets on plane well and can be tuned for more holeshot if you like. Holds in the corners and has an excellent midrange - which is what I like. Loses about 2-4 mph over a 3 blade in top speed but since I run a lot of rougher water that is a nonissue.
I haven't any issues using it in reverse. Backtrolls fine as well but I wouldn't normally use it for that.

Went through 3 props in 3 years, due to damage?

[Buckhead]

Went through 3 props in 3 years, due to damage?

No the props flexed and got visible cavitation burns. Then they wouldn't hold and top speed decreased another 4-5 mph.

No damage just a poor prop for the recommended usage.

[IL Bar]

So is the pitch and size stamped on the prop?
Is there a performance difference between aluminum and stainless?

Yes it should be stamped on the hub of the prop.

I’m sold on stainless after buying this prop. The new props have a shear hub kit that shears if you happen to hit something. It will save your gears but you still might bend your prop shaft.

Give Recreation Power sports in Edmonton a call. I learned more about props in five minutes from that guy than anywhere’s else. Tell him what you have and what you want to accomplish and he’ll have a recommendation or two for you.

[elkhunter11]

No the props flexed and got visible cavitation burns. Then they wouldn't hold and top speed decreased another 4-5 mph.

No damage just a poor prop for the recommended usage.

My plan is to put a few hours on the engine, then see what pitch I need, then buy an X7, and keep the aluminum prop as a spare.

[dutchman]

Boat has a inboard 6 cylinder 3.? L engine.

First what engine do you have?
Here's a couple things I've learnt by trial and error.

5 blade props are great for pulling down low, but you need power to do so. At holeshot, a 3.0L does not have enough torque to take advantage of the 5 blades.

As for the spitfire 4 blade. that was the best prop to use on my 18.5' bow rider with 4.5L Merc engine. Comparing a Merc Black Max and Spitfire (both with proper WOT rpms). The 4 blade out performed in every aspect, pulling, smoothness, sharp turns, etc. And there was no loss in MPH.

[alxwang]

My current prop is Mercury Black Max (9 3/4 x 9 1/2"). Can I change it to Mercury Black Max (9 1/4 x 12 1/2") or Mercury Black Max (9 1/2 x 11")? If I can, will the change make my boat faster. The engine is 25elh and the boat only can do 22 mph at the top throttle now.

[elkhunter11]

My current prop is Mercury Black Max (9 3/4 x 9 1/2"). Can I change it to Mercury Black Max (9 1/4 x 12 1/2") or Mercury Black Max (9 1/2 x 11")? If I can, will the change make my boat faster. The engine is 25elh and the boat only can do 22 mph at the top throttle now.

You need to know the rpm at top speed now. If the boat is at the maximum suggested rpm, or slightly above, you could likely gain speed by going to a prop with more pitch. If the rpm is less than the maximum recommended rpm, you could lose top speed, and you will lose acceleration.

[EZM]

It all boils down to what kind of boat weight and engine is pushing it and what you need or want your prop to do.

Most of the comments posted above are true ........ but everything is a trade off ....

I choose NOT to take advantage of the little bit of extra performance I might get out of a stainless prop because when I do hit a stick, log, etc.. I know the prop is easy to bend back, or fix, or cheap to replace AND it's it's less likely the hub was spun to the point I have damaged my lower unit. I like that piece of mind and a top speed of maybe +3-4 mph isn't really noticed when I'm already going 50mph on the water.

In fact, I pitched down my prop even further, so max speed dropped to 45mph, but the better low end, hole shot, and boat control at low speeds is far more of an advantage to me when docking, loading, controlling my boat when needed.

As far as a 4 or 5 blade being "worse" in reverse, I was not aware that it would have made a huge difference - but, again, anytime you change up a prop, the performance characteristics will have changed so it makes sense.

[tri777]

Be neat if some genius invented an adjustable prop one could adjust while boating in real
time like an airplane prop, lol.

[Buckhead]

Be neat if some genius invented an adjustable prop one could adjust while boating in real
time like an airplane prop, lol.

I believe there are some props like that. Not completely variable but like a 2 speed that will switch between say a low 15 pitch to high of 21 depending on the setting.
I don't know anything else about them or how much they cost, but probably fairly pricey.

[EZM]

Be neat if some genius invented an adjustable prop one could adjust while boating in real
time like an airplane prop, lol.

I think some of the bigger boats (more like ships and yachts) have props like that ...... I bet it would be cost prohibitive for small vessels like the ones we run up and down the lake.

[Ronbill]

.....Give Recreation Power sports in Edmonton a call. I learned more about props in five minutes from that guy than anywhere’s else. Tell him what you have and what you want to accomplish and he’ll have a recommendation or two for you.

I agree with this ^^^ 110%!
Call them and ask to speak with Andreas the 'Prop GURU'. You will get all you need for answers.

He helped me with my 19.5' Chaparral 196SSI bowrider with 4.3L Volvo I/O engine. Long story short, I also wanted more hole-shot for watersports so I replaced the OEM 3-blade SS 14.75" x 19" pitch with a Turning Point 4-blade aluminum 14.5" x 17" pitch. I lost 3mph at wide open throttle, but gained in hole-shot and hook-up in sharp turns. I find the loss in reverse torque to be minimal compared with the 3-blade.
While aluminum (AL) will generally flex more than SS, the newer AL props minimize this. And you will appreciate AL if you ever hit rocks as the AL breaks off or bends much easier than SS (I found out the hard way at Gull Lake one summer). They are much cheaper to replace than SS too. Lastly, the AL prop is lighter than the SS and will spool up a bit quicker helping with hole-shot.

[brewster29]

I believe there are some props like that. Not completely variable but like a 2 speed that will switch between say a low 15 pitch to high of 21 depending on the setting.
I don't know anything else about them or how much they cost, but probably fairly pricey.

Variable pitch props were a thing at least 60-70 years ago. They had their own set of problems. They are available still, check out Pro pulse.