Done with #@!! ProPulse

drjohn71a · Posted: Thu Jun 28, 2007 2:54 pm Post subject:

Pat,

Relating to your question with the picture, "Anyone care to hazard a guess.."

I'm not an engineer, but I have worked on some injection molding designs and designed several injection-molded devices. Also, we cast things alot in the Dental field.

It looks to my like that product has a two-fold problem. One is in the design, which leaves a minimum of material, a rapidly diminishing bulk, right in an area of heavy load.

The other is that, unless special care was used in locating the injection ports, two 'blobs' of molten material are meeting exactly in that weak design area.

The right angle fracture line is not the way a piece of well-injected, glass-filled polycarbonate would break. It is a weak spot.

Design and manufacturing problem - that's my take on it.

John

Sea Wolf · Posted: Thu Jun 28, 2007 5:09 pm Post subject:

Sorry Tyboo, I stayed overnight at the lake, where the marina and esort don't have Wi-Fi (good)_

The myth about stainless props damaging lower units and engines fails to take into account the rubber slip bushing that replaces the sheer pins found on much older motors (anybody else remember those things?)

I bought a new stainless prop the the new Yamaha two years ago, but eventually took it off because I didn't like the big bump/clank when shifting. A 14 lb stainless prop is a lot more massive than a 4 pound aluminum one, and shifts like it.

I also bought a 4 blade aluminum Solas, but the difference between that and the OEM three blade wasn't all that significant.

So I've returned to aluminum props, and buy ones that were taken off motors that had stainless replacements put on them. If you watch carefully, you can get them for $50-$60 on ebay, which is cheaper than repairing your existing prop at the typical prop shop. Small repair jobs I can do myself.

Joe.

tom&shan · Joined: 21 Sep 2006 Posts: 316 Photos: Dakota

JimD · Posted: Fri Jun 29, 2007 12:00 am Post subject:

Sea Wolf · Posted: Fri Jun 29, 2007 12:04 am Post subject:

JimD-

You wrote:

"I am not in total agreement here.While the "slip" bushing indeed acts as the old sheer pin with rotational inertia, preventing shaft twist or spline breakage; a lateral impact which would deform an aluminum prob could bend a shaft, bend a spline, and thus affect the gears as well. In other words, if you hit something hard enough to break blades, there is probably enough lateral force generated to cause damage. An aluminum or composite prop would minimize collateral damage."

And I agree! Thanks for pointing it out.

Joe.

TyBoo · Posted: Fri Jun 29, 2007 12:33 am Post subject:

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.

Pat Anderson · Posted: Fri Jun 29, 2007 12:54 am Post subject:

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 · Posted: Fri Jun 29, 2007 1:51 am Post subject:

Sea Wolf · Posted: Fri Jun 29, 2007 8:14 am Post subject:

Pat Anderson · Posted: Fri Jun 29, 2007 9:08 am Post subject:

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...

Alasgun · Guest

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

Sawdust · Posted: Fri Jun 29, 2007 11:21 am Post subject:

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

Pat Anderson · Posted: Fri Jun 29, 2007 11:24 am Post subject:

Yes, I might just take him up on that...

dogon dory · Posted: Fri Jun 29, 2007 4:33 pm Post subject:

Sorry, Folks - Post Deleted By Author

journey on · Posted: Fri Jun 29, 2007 8:43 pm Post subject:

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