Done with #@!! ProPulse

I'm on the fence here, but it seems to me a lateral impact of sufficient force to bend the hardened steel shaft would go right through the aluminum blades in an instant and apply its force onto the hub which will not cushion the impact much more than a stainless blade. Simply put, I think if you swing the sledgehammer hard enough to bend the shaft it won't make any differene what type of material is between the shaft and the hammerhead.

I have a stainless prop for my 130 with too small a pitch, but I have used it when heavily loaded and when a blade on an aluminum just up and fell off I used the stainless until I got a replacement. If it was 15" instead of 13" I would use it all the time. One of the most frequent complaints about the much heavier SS prop is a damaging "clunk" when shifted in/out or between gears. I didn't notice that much myself.

I have been lucky enough to avoid anything big enough in the water to damage a prop, so I would still buy aluminum if I needed one simply because of the cost for SS.
 
OK, the prop on the BF150 right now is the 14.5 x 15 x 3 SS that came with it...it performs terribly, this is too small something...the new aluminum prop on order does not have a greater pitch - it has a bigger diameter, 15.5 x 15 x 3... This is what Les recommended for David on Anna Leigh, although it was SS...not more pitch but bigger diameter. The ProPulse performed much better, worked great at 15 pitch setting, lugged awfully when set at 16 pitch. If it were sturdier, I would continue to use a ProPulse for the performance. So what is the significance of diameter versus pitch? I will really be bummed if the new prop does not outperform the current prop...







TyBoo":n1r5mlbr said:
I have a stainless prop for my 130 with too small a pitch, but I have used it when heavily loaded and when a blade on an aluminum just up and fell off I used the stainless until I got a replacement. If it was 15" instead of 13" I would use it all the time.
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TyBoo":3q44f94v said:
So what is the significance of diameter versus pitch?
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Uh oh.
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Uh oh, indeed, here we go again!

They are related, of course.

Pitch determines the theoretical speed through the water, and is usually thought to be "right" when slip (the difference between theoretical speed and actual speed) is about at 10-15%. Some slip is unavoidable in a fluid, period, and the 10-15% works out as optimal, empirically.

Concurrently, the prop diameter is also involved in the determination of slip in that it is a measure of prop surface area which allows more or less slippage. Too large a diameter, and the prop slips too little and the extra drag from the extra surface area wastes energy. Too small a prop diameter results in too much slippage, and extra energy is lost through the excessive fluid friction created.

I guess size does matter! :teeth

Joe.
 
Well, what matters is the speed I can make for the RPMs the engine is turning...forget wind and current for a moment, this is only an example, with the Honda SS on the boat right now 4500 RPMs might give us 12 knots but the ProPulse gave us 17 knots...the performance difference was that great. Of course, the ProPulse had the same pitch (15), but a larger diameter and four blades (or four blades most of the time!). But David gets much better performance it seems with his Honda 15.5 x 15 x 3 SS than we get with our Honda 14.5 x 15 x 3 SS, where the only difference is an inch of diameter...
 
One comment on this prop thing. I am running a Honda E15-17L 3 blade Alum. on our 25ftr (150Honda) and at 5500 I will do 29knts! I burn 2.5 to 3.3 GPH with this arrangement, and have decided this is fine. I'm happy with the performance, any faster would be scarry. I think sometimes we get too far out in left field looking for something magical which many times doesn't exist. I have quit searching, I guess the factory doe's know what there doing!
Mike
 
Pat,

In some things size matters. An inch is very important in prop diameter too. Not rocket science, I know, but prop design is close. I like stainless for many reasons - in the long run they are cheap vs replacing or refurbishing aluminum, they do not flex (deform) as much as aluminum under varying loads, they usually are not damaged when chopping up light drift -- I know, I've seen stainless props destroyed -- but in my personal experience, and watching props come through the shop for over 20 years, stainless is the preferred way. OK, my preferred way. YMMV

An exception - on the contra-rotating props I've seen two stainless props destroyed beyond repair by a stick caught between the props. :cry

When testing various props for a boat (done quite often) we always have several props aboard - check for max RPM, RPM at cruise, etc. If possible we check fuel flow vs RPM to try and get a fuel consumption curve...

Borrow one of David's props?

Duster
 
OK, I went out this afternoon and here's what I found. First, though, the boat is laded for cruising: clothes, food, etc, etc, full gas, full water, full coffee jugs, full head.

The Apollo 16" pitch 4 blade certainly works better than the Honda 3 blade 15" pitch. Cruising at 8 knots, the boat is getting 4 nmpg. Cranking it open, at 5500 rpm the boat is at 25.6 knots (29 smph?) and is really riding smoothly. Maybe 2 nmpg. To get there, I have to retract the trim tabs above 20 knts. Also for those of you that had hot rods, you can feel the engine "come on the cam" at 4500 rpm. Fun then and fun now. Please note that the tach is acting up and the rpms are approximate. By the way this is in fresh water, which doesn't offer as much buoyancy for what that's worth.

I'm happy, and from what I've seen the stainless clunks into gear, but survives hitting things. The plastic prop doesn't, and it's no manufacturing defect. No comment on Al, but it's strength is less than steel.

Boris
 
I purchased a back up Pro pulse for the CD 25--and it will be a "get home" prop. I have a back up aluminum prop also (from another boat--not sure if it will repitch exactly, but the boat and engine were about the same size). I run a SS prop, on all of my boats (except the dinghy) and am really sold on them.

HOWEVER--I had a bravo III unit 300 hp I/O on another boat, with counter rotating SS props. I hit a 1" stick at idle speed--stalled the engine, and I didn't think much about it----until a few weeks later the engine would not start. It turned out, that the 1" stick caught between the counter rotating props, had knocked one gear tooth off the lower unit gears--and one tooth, leads to two teeth etc--eventually when I changed out the oil--out came multiple teeth!

I would not be surprised that the Pro Pluse hit a small object and that was enough to cause the problems--I have also spun the hubs out of props, but that is not always a guarantee that the lower unit or prop will be protected.....
 
I am totally sold on the new "gummy bear" props that are out.
impervious to damaging anything in the lower unit, and as a neat side benefit, they don't taste all that bad either!

:lol:


James
 
OK, the 15.5 x 15 x 3 AL (Quicksilver, a Mercury product I guess) prop is on, and the first test will be tonight when we launch at Blaine and cruise around Birch Point to anchor out in Birch Bay for the fireworks show. We shall see...the 14.5 x 15 x 3 SS Honda prop has done OK, am glad to have it as a backup, but it spins up to too high an RPM for any given speed, and I'm pretty sure WOT would take her right past the redline and blow up...
 
Don't know if this will help since I have twin 80's, but I'm running 3-blade aluminums (original with Yami's), 13.5 x 15P". I paid close attention to this last trip's run, at 4,000 rpm with 5 people, 3 days gear on board, and dive gear for two, my GPS speed was 14-14.5 knots. This seems to be on the 'knee' of an efficient plane, just a couple hundred more rpms the speed is up to 16-16.5 knots. WOT is slightly too high, about 6,000 rpms, but I like the torque at slower speeds for maintaining a plane in heavy seas without having to jocky the throttle.

Good luck with your tests Pat, keep us posted!
 
Wowwie zowwie! Performance and economy are DRAMATICALLY better with the 15.5 x 15 x 3 AL Quicksilver prop compared to the Honda 14.5 x 15 x 3 SS prop! I will record some real numbers on the Gulf Isand cruise, but for starters, running to/from Birch Bay, 3800 RPMs are giving me about a 14.5 knot cruise and 4500 RPMs about 19 - 20 knots...
 
I would love to answer that question, but our Navman is SO far out of calibration that I hesitate to answer. Relative improvement in economy was on the order of 30% with the new prop. As I say, I will have some real numbers after the Gulf Island cruise...

journey on":fehvccri said:
Hey, Pat, what was the mileage? And how heavy were you loaded?

Boris
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