Stainless Prop Journey

[SamSteele]

Thought I would put this up as an info post. My boat is a Lund 1850 Impact XS with a 150 Merc 4 stroke, 9.9 ProKicker, and a 24V bowmount. I had a 19p Black Max aluminum 3 blade prop on my boat last year. Top speed was 46 mph on GPS, 5600 rpm, under 1/4 trim adjustment before blowing out, blowing out on corners unless trimmed down and throttle reduced, and blew out when pulling a slalom skier from a deep water start unless the throttle was eased.

That 3 blade aluminum got dinged up last fall at Pigeon Lake PP boat launch so I figured it was a good time to try a 4 blade, hoping to get rid of the blowing out issue. I put a 19p 4 blade aluminum Quicksilver Nemesis on as a replacement. It was cheap and I thought it would be pretty similar to the 3 blade, with less chance of blowing out when pulling a skier or cornering. Tried it out this spring and found it to be terrible on my boat. Top speed dropped to 42, even less trim adjustment, 5200 rpm, blew out on any corners. Couldn't hit full throttle without it blowing out. Overall, not a good fit for my unit.

I went to my dealer and picked up a Merc Tempest Plus 3 blade SS in 19P. I was going to try a Rev4 in 17p but they didn't have one in stock, so I figured I would try this one out first. This prop has the PVS plug system in it and comes with "Large" holes. I picked up some solid plugs as well based on my reading, as they recommend them for 4 stroke motors. I put the prop on and ran it over the weekend, using the same Flo-Torq2 hub kit that I had with the Black Max props. There was some prop rattle in reverse, but it went away in forward even at an idle. Holeshot was about as fast as with the original 3 blade aluminum prop, but there was a different feeling about it. I think the large plugs are causing that, so I will be switching to the solids. The boat hopped on place nicely and top speed (with just me, 3/4 tank of fuel, and my 24 plano boxes full of tackle) was 50.1 mph in a light chop. RPM was 5600. Trim was double what I ever had before, and I could crank the wheel at a high rate of speed and not have any cavitation. I towed the kids on a 3 man tube and it handled that like a champ. Once I put the whole family in the boat with all our stuff (two adults and 3 kids) my top speed dropped to 48.3 mph. Handling remained unchanged.

Overall, I cannot believe the difference that a SS prop made to the handling of my boat. I care less about the top speed than about the prop staying "hooked up" when cornering. I will be changing out the PVS plugs for solids and think that will help even more. My motor is also on the second lowest hole. I think I may get it raised one more hole and see how that works. A little less leg in the water should help a bit too.

I hope that this post was informative for anyone contemplating the move to a SS prop. They aren't cheap, but it made a very noticeable difference on my unit.

SS

[nast70]

I was in the process of picking up a SS prop at the store when I over heard a conversation between a customer and a service tech. They were talking about the exact same thing and the point of the conversation was how SS won't break if it hits a rock etc. The end result is the risk of more extensive damage to the leg, motor etc. The aluminum prop is the weak spot, easy to replace, even on the water, and cheap insurance against engine or leg damage.
I left the SS prop on the counter and bought a replacement aluminum.
I'm not surprised at the loss of top speed with the 4 blade. Although hole shot is better with the increase in lock up, there is more drag as well.

[SamSteele]

The Flo-Torq hub system is designed to spin if the prop hits a rock, thereby saving your lower unit. You would need to get a new hub kit, but that should be it.

SS

[EZM]

Originally Posted by nast70

I was in the process of picking up a SS prop at the store when I over heard a conversation between a customer and a service tech. They were talking about the exact same thing and the point of the conversation was how SS won't break if it hits a rock etc. The end result is the risk of more extensive damage to the leg, motor etc. The aluminum prop is the weak spot, easy to replace, even on the water, and cheap insurance against engine or leg damage.
I left the SS prop on the counter and bought a replacement aluminum.
I'm not surprised at the loss of top speed with the 4 blade. Although hole shot is better with the increase in lock up, there is more drag as well.

Precisely why I will not use a SS prop.

To get largely incremental performance improvements at the risk of destroying your entire lower unit and being left without the ability to continue your vacation or trip isn't very smart in my opinion.

Yes - you might go from 40 to 43 mph, yup you might actually improve hole shot and handling, you might even find better fuel efficiency at 3%-5% but at the end of the day, I'm not tuning a performance race boat. I'm putting a prop on my boat that will likely find a sand/gravel bar at some point.

When using an aluminum prop, and should something occur (like hitting a sand/gravel bar), which it will if you have every owned a boat, I like the fact I can pull the boat, swap the hub and prop at the lake in 20 minutes and be back out burning around like nothing happened.

Using a SS prop - the same gravel/sand bar can become a $10,000 lesson for someone who may eventually learn the hard way. I'm sure the wife and kids enjoyed the extra 3mph with the wind blowing through their hair on their Okanagan vacation. But I'm also sure they won't enjoy having to stare at all the other boats for the rest of the week because your lower unit is destroyed.

Seen it happen more than once.

JMO

[Walleyedude]

Stainless props make a world of difference on any boat, but especially on boats with 150+ HP.

Modern hubs like Merc's Flo Torq II prevent damage to the gearcase (and the prop to some extent) by failing on impact and allowing the prop to spin freely on the hub. You really don't have anything more to worry about with a stainless prop compared to running an aluminum prop other than the cost of the prop itself or prop repair. If you hit something hard enough to damage the gearcase with the Flo Torq hub, you'll have damaged it with an aluminum prop too.

The Tempest Plus is a good prop. It's fast, and easy to spin. The downsides are that you will get some prop chatter/clunking, and it's designed to give mostly bow lift, which is great for top speed, but generally means slower planing times, higher min. planing speeds, and the potential for some handling issues, especially in rough water, depending on the hull.

The new generation of 4 blade props - the Bravo series (FS or LT), Rev 4 and Spitfire (for lower HP) are better choices in my opinion. I call them AWD for your boat. You'll get better hole shot, lower planing speeds, increased overall lift with a flatter ride, and superior handling under all conditions. Top speeds with a 4 blade will be within +/- 1-2 mph either way compared to a 3 blade depending on your exact setup. The 4 blades do like to be run higher than a 3 blade for optimum performance.

I like to run the PVS holes fully plugged, especially on the four strokes. I find that I get a lot more cavitation and the boat speeds tend to "surge" or "hunt" when using using plugs with holes in them. That drives me crazy. I can tell right away just by throttle response and sound if I lose a PVS plug.

[SamSteele]

Originally Posted by Walleyedude

Stainless props make a world of difference on any boat, but especially on boats with 150+ HP.

Modern hubs like Merc's Flo Torq II prevent damage to the gearcase (and the prop to some extent) by failing on impact and allowing the prop to spin freely on the hub. You really don't have anything more to worry about with a stainless prop compared to running an aluminum prop other than the cost of the prop itself or prop repair. If you hit something hard enough to damage the gearcase with the Flo Torq hub, you'll have damaged it with an aluminum prop too.

The Tempest Plus is a good prop. It's fast, and easy to spin. The downsides are that you will get some prop chatter/clunking, and it's designed to give mostly bow lift, which is great for top speed, but generally means slower planing times, higher min. planing speeds, and the potential for some handling issues, especially in rough water, depending on the hull.

The new generation of 4 blade props - the Bravo series (FS or LT), Rev 4 and Spitfire (for lower HP) are better choices in my opinion. I call them AWD for your boat. You'll get better hole shot, lower planing speeds, increased overall lift with a flatter ride, and superior handling under all conditions. Top speeds with a 4 blade will be within +/- 1-2 mph either way compared to a 3 blade depending on your exact setup. The 4 blades do like to be run higher than a 3 blade for optimum performance.

I like to run the PVS holes fully plugged, especially on the four strokes. I find that I get a lot more cavitation and the boat speeds tend to "surge" or "hunt" when using using plugs with holes in them. That drives me crazy. I can tell right away just by throttle response and sound if I lose a PVS plug.

Hey Walleyedude,

I was actually looking for a Bravo FS or Rev 4 to try for my unit, but my dealer didn't have the Bravo FS in stock and the Rev 4 they had was a 19p. I figured I should go with a 17p Rev 4 in order to keep my RPM up. I may still look at them down the line, but for now I'm going to put the solid plugs in and see how I like it. I may look for a used Bravo FS 20p or Rev 4 17p down the line, just to try it.

SS

[Walleyedude]

Originally Posted by SamSteele

Hey Walleyedude,

I was actually looking for a Bravo FS or Rev 4 to try for my unit, but my dealer didn't have the Bravo FS in stock and the Rev 4 they had was a 19p. I figured I should go with a 17p Rev 4 in order to keep my RPM up. I may still look at them down the line, but for now I'm going to put the solid plugs in and see how I like it. I may look for a used Bravo FS 20p or Rev 4 17p down the line, just to try it.

SS

Both great choices.

The Rev 4 will handle better overall in my experience, especially with bigger loads or in rough water. They're hard to turn though, so the 17P is the right choice. They're slightly slower than the 3 blades and Bravos at WOT, but in my opinion the trade off is well worth it. I run a Rev 4.

The Bravo FS will give you all the advantages of the 4 blade, and on your relatively light hull, should be as fast or very close to as fast as the Tempest.

[Ken07AOVette]

Huge fan of stainless, I won't run aluminum on any boat

[EZM]

Just found an interesting article.

http://www.boats.com/resources/which.../#.WUgbRk2GOpo

If, in fact, we trust the technology on the torque hubs or sleeved hubs to protect your lower unit then maybe my worry about exploding my lower unit might be overstated.

I realize for major impacts, it just doesn't matter what your prop is made from - your day is gonna suck.

[SamSteele]

Here's a good video on the hub systems. They work with other brands of outboards too. Usually you just need a different thrust washer that is specific to your motor.

https://www.youtube.com/watch?v=2-lhtReopcI

SS

[Headdamage]

People hit a lot of rocks here on Great Slave Lake and stainless steel props are not popular because of the damage they can transfer into the motor and the cost of replacing them. I run an aluminum prop with a replaceable hub. I've tried a prop with polymer replaceable blades but it had a noticeable loss of performance over the aluminum prop of the same size and pitch.

[couleefolk]

I run stainless most of the time, unless I'm running a shallow lake that I will be hitting bottom, in which case my prop would have to be sent away for awhile to get fixed. The performance on my heavy Crestliner with stainless is much better, especially when I'm hauling a couple of tubes, or want to jump the boat onto the step. I'm not scared of running a stainless.

[Ken07AOVette]

since we are on the topic, I have a couple Mercruiser 4 and 5 blade stainless props cheap, from a 5.0 if anyone needs 1. They fit most anything, use the hub system. One is a raker, one is a shooter iirc. They are not new but definately useable.

[hunter0968]

What pitch are they ken. I only have a 3.0l merc, was wanting to try a 17p high five. Hard to get over the 900 dollar price tag. I honestly don't think a stainless prop will help on such a small engine. Only reason I want to try is for that reason, to see if it makes a difference.

[Ken07AOVette]

they are big, 5 blade is a highfive 48-815762 a45 23p, think the 4 is a 21

[deschambault]

Just a confirmation on SS vs aluminum. I hit a piece of granite on Lac La Ronge with a SS prop. The local shop straightened the prop shaft to the point it was serviceable for the two days I had left on that trip but after two more days it started vibrating badly. I had the drive shaft, pinion bearings and prop shaft replaced - $4000 quite a few years ago. Nothing but aluminum on my boats since.

[EZM]

Originally Posted by deschambault

Just a confirmation on SS vs aluminum. I hit a piece of granite on Lac La Ronge with a SS prop. The local shop straightened the prop shaft to the point it was serviceable for the two days I had left on that trip but after two more days it started vibrating badly. I had the drive shaft, pinion bearings and prop shaft replaced - $4000 quite a few years ago. Nothing but aluminum on my boats since.

Kinda where I was worried a bit - just thinking about it .... and your experience sort of reinforces my paranoia a little.

The difference is ..... if you are talking about a sacrificial hub designed to prevent the damage caused to the gear case when a prop suddenly "stops rotating" when it jams up in a log or rock and strips some gears then the sacrificial hubs will work well in a SS or Aluminum prop. I can see how that would eliminate the concern in this particular application.

But - If you actually hit something - I'm thinking aluminum is far more likely to bend, deflect and crumple absorbing the impact that otherwise would be transmitted to the shaft compared to a solid unforgiving material like a hard SS.

I'd say, in either case, having a sleeved hub (most new props for bigger engines do now I think) is a good policy. All of mine do (and I run aluminum).

I guess my point is there are two different scenarios there - that end up with 2 different outcomes.

One is the damaged caused by the sudden interruption of the rotation (causing a speed disparity between the prop and prop shaft) and the other an impact which applies force from the prop to the shaft itself in a direct hit.