Great Day! (Honda props)

[Mikebe]

Ok, it's Friday evening, I'm sitting on my new Mac, (still think of it as new, but I've had it a couple months now) watching TV, drinking a Jim Beam and Coke and writing this post after a truly great day. I left work early today, and pulled my Mac out of the water for the first time to install the stern rail seats I ordered from BWY. No problems getting the boat on the trailer. I pulled out, and drove forward about 30 or 40 yards, heading for the edge of the paved area so I could park out of the way and work on my boat. I heard someone yell just as I hit the brakes and killed the engine. I got out, looked around, and noticed someone pointing at my mast. I looked up. It was four feet shy of the power line I hadn't seen. Luck was with me, for sure. I got the stern rail seats installed, and decided to try out the new replacement propeller I'd gotten in. It was a replacement of the original propeller the boat came with, (which I had managed to destroy against a dock ladder before I even got a chance to really use it). I had been running with a dog-eared 11.25 10 pitch Quick Silver, which I thought was pretty good, but didn't seem as good as the original. So I went out and tested the new replacement prop (an 11.75 10 pitch three blade, not dog-eared). It wasn't as good as the Quick Silver. I have a lot more weight on the boat now, and the replacement prop started cavitating at about two thirds throttle and felt like it was spinning in air.

Not happy, I went back to the boat ramp, backed in, and installed the dog-eared 4 blade Michigan Wheel 12 in 10 pitch I'd gotten in but never tested. Oh man, what a difference. I noticed it right away, pulling out at idle. Smooth, moving a lot of water. Churning up mud from the bottom that I never saw with the three blade props. OK, this was looking good! I opened up the ballast valve and headed out, slowly inching up the throttle. By the time the GPS said 10 knot, the ballast was empty, and I inched the throttle on up, 11 knots, 12 knots, 14 knots...I started to see something I'd never seen before, massive walls of water sheeting away off the bow. The boat was CRUISING! People in other boats I were looking on in amazement. It was awesome. I've found the right prop for my boat. Not looking any further.

So I went back to my slip, and during the docking procedure, sat on my relatively new West Marine Aluminum boat hook as it lay across the cushions in the cockpit. I had just spent two weeks making a homade boat hook, with a heavily urethaned Ash handle and classic brass fitting, and had just told the admiral the day before that the homade boat hook really had no advantages over the 39 dollar aluminum one. Don't know if the homade one floats, it's heavier, etc. but it was more valuable because it was unique. Well, let me tell you, a wooden handled boat hook is a lot more DURABLE than the aluminum ones. The aluminum one I sat on folded like a pretzel. The wooden homade one is the one that got me home. Couldn't have had a better day.


Mod's note: 'conclusionary emphasis' added ~fc

[tlperrine]

Well said! Just another fine day in the boating life. Fair winds, Terry

[NiceAft]

Mikebe,

With all of that, and you can write too

When is the next addition to the serial of "As the Mac's prop turns" Where will our man turn up next, and what adventures await him around the bend in the water?


Ray

[Mark Karagianis]

Mikebe, what's your top speed & rpm with full tanks, couple crew & no ballast?

Mark

[Mikebe]

I got up to about 15 knots, on the GPS...just me, no ballast, but probably 200 lbs of other stuff on board.

Don't know RPM, but I'm sure it was less than with the three blad props at WOT

[argonaut]

Wow Mike... very impressive! The prop made a big difference you think?
My X w/honda 50 has always thrashed a lot and lifts the the bow but doesn't make the kind of speed I think it's capable of. It also seems to cavitate but I'm no power boat guy, I really am not sure.
I repropped with a 4 blade Solas Amita 11.8 X 9, but no major difference, except a weird "'singing" sound at the prop. I mainly sail anyway, but now I'm wondering...
Exactly which Michigan prop is this? Any pictures?

The collective seems to say that all props are not alike and we need large surface area (big dog ears), so why don't props list their surface area along with pitch and diameter?

[Mikebe]

This is what I ordered from iboats.com...

Code: Select all

Product                                Qty   Price  Extended 
113     Honda (35-50 HP) Hub Kit         1   $24.99  $24.99  
992403  Mich. Wheel Vortex Aluminum 
        4 Blade 12" dia x 10" pitch SR   1   $58.99  $58.99  

I'm not an expert on props, I understand I won't get the best speed out of a four blade prop, all I can say is I am very satisfied with this one. I like the smoother operation, pickup, and response at lower rpm's and am happy to trade some top speed for it, since I never intended to run more than 10 - 12 knots anyway.

I'll try to post a pic tomorrow...


Mod's edit: to clarify order info for M.W. Vortex prop ~fc

[Frank C]

Robert is our "resident expert" with probably with the most experience, interest and knowledge of propping the various Mac hulls. His advice ((paraphrased from the archives) might be '... the speed penalty that's commonly associated with 4 blades is for the more common boat hulls, that reach speeds greater than 35 mph.'

The penalty is caused by the greater friction of an extra blade at those higher speeds. By contrast, when the boat barely approaches 20 mph, excess friction hardly enters the picture ... so the penalty is much less significant.

I'd much rather have a 4-blade on my Suzuki-60. I have 2 or 3 of them sitting in my garage. Unfortunately, have not found an appropriate blade profile at 11-pitch.

[Mikebe]

Ok, I went out today and did some more testing. I'm sorry to report I found a weakness with the Michigan Wheel 4 blade prop. I retested the prop without ballast, with pretty much the same results as before, full throttle between 14 and 15 knots on GPS, all good. Then I flooded ballast, and repeated the test. What I found is that with the ballast full the prop will begin to spin on the neoprene fitting that attaches the prop to the shaft of the motor at about 11 knots. The neoprene fitting simply is not strong enough. At this point, I have no way of knowing how close I was to experiencing this slippage with empty ballast, another person in the boat might be all it would take.

So, after reading a post by Admiral Moe that suggested to me that my testing of the original Honda 3 blade prop a couple of days ago might have been flawed due to an oversized thrust washer, I decided to re-test the honda prop. This time I removed an extra washer that I had left in place during the first test, and this allowed the prop to fit into place the way it is obviously supposed to, and I did not have to bend the cotter pin to get it through the castle-nut. This alone was enough to convince me that Moe was probably right, in my first test, the prop had not been seated far enough forward to prevent exhaust gasses from escaping in front of the blades at high RPM. It had felt like my prop was spinning in air...well, almost. If Moe was right, my prop had been spinning in exause gasses.

So I went out and re-tested the Honda OEM 3 x 12 x 10 pitch, and this time with much better results. With no ballast, between 15 and 16 knots GPS, with ballast, same as the michigan wheel. Around 11 knots with ballast is all it will do. Don't know if it's slipping like the Michigan Wheel, or cavitating, but I suspect it's slipping. I know the michigan wheel was slipping, as I was able to remove the neoprene fitting and examine it and see the damage cause by the slippage. The honda prop appears to have a similar "slip" capability in it's design, but unlike the michigan wheel, it's sealed and I can't look inside.

So it seems to me that if I could weld either of these props to the shaft of my motor so they wouldn't slip I'd be fine, with or without ballast.

I'm seriously considering a judicial application of 5200 to the neoprene fitting for the michigan wheel before re-assembling it for another test. I think a little 5200 might be all it would take to fix the slipping problem.

[Robert]

I think the MIWheel people own you a new prop with a better fit pressed in rubber hub, if you can slip it rather than slow down the motor with load, the prop is defective.
..
The Solas Amita 4 blade has a different hub, no press fit rubber, more room for free flowing exhaust etc.. Here is a 9 pitch four blade that would be a good one with a Honda or Suzuki 50Hp (same prop RPMs with slightly different engine RPMs and gear ratios) pushing a Mac26.
4 X 11.8 X 9 SC-KT 58100-94302-019
..
http://www.solas.com/products/propeller ... 20OUTBOARD

[Mikebe]

Thanks for the info. I will try the Solas Amita 4 for the Honda 50, 4 blades, 11.8 diameter, 9 pitch. Should get it in next week sometime.

I did some searching on the internet on "michigan wheel slipping" seems I'm not the only one having the hub slippage problem...

The MW prop was $60 and the hub kit with the neoprene fitting $13. It's not worth the hassle to me to bother with persuing MW for a replacement hub kit. I could be mistaken, but think I would probably spin through any number of replacement hub kits. Somehow I don't think it is a defective product, but rather a poorly engineered solution to mounting the prop on the shaft. It is a simple mechanical fitting. If it were well engineered for a 50hp motor, I would expect it to take at least a 200hp motor minimum to make it slip...

Hopefully the Solas prop won't slip. It's twice the price of the MW prop, we'll see if the old adage "you get what you pay for" holds true.

[Terry]

As an alternative, the Solas Alcup series 4 blade, same size would work too. The Alcup has a medium cupping on the edges to provide more grip and better bite on the water, every advantage helps.

[Mikebe]

After spending some more time researching the issue of hub slippage, I'm beginning to doubt that is what is happening. From what I've been reading, although hubs can and do sometimes slip, it seems that it is actually rather rare, and it also seems that my inspection for slippage was not the way to check for a spun hub. So I will have to re-evalute the situation this weekend. Given how rare spinning a hub seems to be, I simply can't believe I've spun two different props from two different manufacturers. Which leaves me thinking that what I am experiencing with full ballast must be ventilation, either from exhaust gas leaking around the front of the prop, or the prop grabbing air? I guess it could be either...but I would think that if the prop was grabbing air it would be more likely do so with an empty ballast, not full ballast. Also I'm not very confident that I have the right thrust washers or have installed the props correctly...seems like every prop needs a different combination of washers and spacers...

[Mikebe]

I have found that indeed the "hub slip" problem was due to an incorrect thrust washer. Once I put the right one on, the front of the prop hub seated fully into the motor housing and I get no more ventilating at high RPM's due to exhaust gasses. That's all it was. The prop(s) (whichever one you use) must seat properly or you will have this ventilating problem....

Edit:

The Solas 4 x 11.8 x 9 pitch I ordered came in today. It looks like better quality then the Michigan Wheel. It should, it cost twice as much. It also uses the same hardware as the original Honda OEM prop, so no special thrust washer. I'll test it out ASAWP (as soon as weather permits) and post the results. I'll also re-test the 4 x 12 x 10 pitch Michigan Wheel while I'm at it, if I have a thrust washer that will let it seat correctly. I really liked the Michigan Wheel until I tested it with full ballast...

[opie]

I am curious if you completed your prop testing yet? Let us know, if you have. I have a Honda 50 and with full ballast I get to 9 kts at 3600 and 9 knots and surging at 5000. In other words, 9 knots is tops. I have moved my tilt up and down with no success. I don't have my prop size handy to list here, but I am ready to buy anything that works better than what I have (I think it is OEM 3x12x10)
Unless, something else is happening? I'll check washers and such tomorrow.