Michigan/Piranha/Solas Props on Suzuki DF50, 26M

[Robert]

I had a Piranha Propellers hydrofoil on my cavitaion plate when I tested some of my props on my Mac26X. I did not have any ventillation using the 4 blade props, I tested the 4 x 11.8 x 9 and 4 x 11.4 x 10 pitch. I think the 10 pitch is smaller diameter so it does not overload the motor.
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The Solas 4 blades that I tested had a different sort of hub, not the usual heavy rubber pressed in kind. This hub was less of an exhaust restriction and made the whole prop much lighter weight. The 3 x 12.25 x 9 cupped stainless prop that I liked had advertising that says that the less restiction to the exhaust of the stainless prop helps.
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My Mac26X speeds with the Suzuki DF50 and the 4 x 11.8 x 9 were higher than you are getting on you M, but I did my tests with me and the admiral and 3 small children. So lighter load than you have. Also even a small swell or chop on the water will slow you down.
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I noticed that the larger the prop blades and lower the pitch the less the difference in empty and full ballast WOT RPMs. The 4 x 11.8 x 9 gave about 50 RPMs less at ballast full than the 3 x 12.25 x 9 cupped stainless, while they both topped out at 6800 RPMs ballast empty.
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Speed limiter on the Suzuki DF50 is by inherrent torque roll off at 6800 RPMs and by computer control at 7250 RPMs.

[Terry]

The Solas 4 blades that I tested had a different sort of hub, not the usual heavy rubber pressed in kind. This hub was less of an exhaust restriction and made the whole prop much lighter weight. The 3 x 12.25 x 9 cupped stainless prop that I liked had advertising that says that the less restiction to the exhaust of the stainless prop helps.

The Solas site lays claim to a 5%-10% gain in horsepower with their larger exhaust.
http://www.solas.com/products/propeller/aluminum.asp

[Mark Karagianis]

Thanks guys for the feedback.

Robert, I think that your X is faster in light or flat swells than the more pronounced "V" shape of the M. If I was buying a Mac and I lived on a lake or bay, I think that I would (knowing what I know NOW) buy a used X, especially with the cockpit / cabin advantage. But for the Ocean - I'm satisfied. And everything that I have read (this Board, the Owner's manual, the propeller guy, etc) says that we should not use a anti-cavitation plate. Hmmm.

They Theirs, Your suggestion about dropping the centerboard a little is interesting, I had never thought of trying that. I'm lucky enough to be going out again this weekend (two weekends in a row, yea!) and I will have the same boat config and load. So I'll try this.

Terry, yeah, I love the sound of this prop. I did not know that it could make so much of an audible difference. Why did you choose the smaller 11.4 diameter prop? Everything that I have read here and experienced in my testing points towards using the largest diameter prop that you can swing. And no cavitation? Man, you lucked out I think. I'm stuck with this expensive prop so now it's like a used car with lots of miles . . .

Frank, I love my Mac, and I love being able to have the speed and range to jet past the guys who left at 6 am into the light morning wind some 20 miles and then enjoy the glorious cross & downhill sailing for the rest of the day. It's like having your cake & eating it too. And I've begun experimenting emptying the ballast and pulling the CB when (full) running, but it's hard to get the ballast out with the sails up. And yes, for my recent Anacapa trip powering with 6 adults aboard, I was very careful to explain weight and positioning to the crew. This is especially touchy in dealing with the ladies, as they don't want to admit that they HAVE a weight. We always had two of the larger people (see how careful I am?) down below when powering WOT unballasted, and at the end of our trip when we were taking horizontal spray across the beam (See Daysail from Ventura Harbor to Anacapa Island - What a Blast! Events & Venues), you can bet that I was the only person above deck!

Thanks, guys

Mark

[They Theirs]

Mark
Years ago we had an out drive cavitate somewhat as you describe as “Intermittent”. Some senior mariner observed our boat cruising and commented after fishing. Turned out he was correct, our drive was too far back, we moved the drive foreword under the hull about one hole. The Drive would still cavitate at times when we picked up some air over big swells, but it would lock-up without having to throttle back. I know you’ve already made all available adjustments, so I’m just bringing up old times.

[Terry]

Mark,
When I chose my prop it was a bit of a crap shoot and at the time I was more focused on pitch even though my research pointed at diameter. I knew I wanted the Alcup 4 due to the built in cupping and 4 blades but I was trying to get close to the 3 X 12 X 10.25 size Hustler prop that the dealer was very successfull with. As it turned out the Solas Alcup I got dropped my RPM's too low so I had to get it pitched down ($45). When the prop guy did the job he did before and after measurements and we decided that 1 & 1/2 inches reduction should give me the 300 rpm I needed. When I picked it up he informed me that the before pitch was 10.5 not the 10 that was stamped on it and that when props are manufactured the stamped pitch is not necsessarily the exact pitch that it has and that variations of 1/2 inch are not uncommon. Anyway I took it with the 9 pitch he reduced it to and tried it out - much to my amazement the RPM's shot up over 6000 RPM way more than we had calculated for so I had to take it back to him and explain what happend. He explained that the pitch inch per 100RPM was not linear in all cases and that in my case the gain was two fold so he re-pitched it back up one half the amount he had pitched it down, (free of charge) so I went from 10.5 pitch to 9 pitch then back up to 9.75 pitch. I now get 5700-5800 RPM which puts me right in the sweet spot for the Honda 50. It does seem that I lucked out with the slightly smaller diameter but I would still recommend the 11.8 diameter to others but also recommend the Solas Alcup as opposed to the Amita.
One of the things I noticed while testing it is that at WOT early in the spring lightly loaded I did get 18-19mph at best and as the season wore on my top end dropped, I guess I picked up weight and growth on the bottom. Another thing I noticed was when I looked back at my wake I could see the anti-cavitation plate was just skimming the waters surface so the blade was not really all that deeply submerged. I suppose the hull pushes the water surface down then the anti-cavitation plate is able to skim the surface more easily but that also brings the prop close to the surface for ventilation so perhaps the slightly smaller diameter comes into play here. I also have to contemplate the difference in hull shape at the transome because the X is more flat there than the M so perhaps the hull shape influences the differences between X & M performance with the same engine & prop. I should also mention that I did a speed test along side another M (same blue hull) who also had the Honda 50 but with a 3 blade prop and his top end was slightly more than mine but I doubt that his mid range speed would be better.
I think that for engines that cannot exceed 12 inches of diameter that either big dog eared three blade props are in order or barring that a four blade prop for extra surface area. The four blades will make the top end suffer but improve your mid range speed and provide better low speed control especially in reverse. There seems to be an awful lot of variables affecting the performance of these boats but at the end of the day after everyone reports in with their results and experiences newcomers should be able to get started on the right track.

[Frank C]

... I also have to contemplate the difference in hull shape at the transome because
the X is more flat there than the M so perhaps the hull shape influences the differences between X & M performance with the same engine & prop. ....

This is first time I've noticed this comment in a prop testing discussion!
While painfully obvious, it is something I've never actually thought of during reading pages of prop stuff. It easily explains why Robert and Mark can have vastly different results from same engine and same prop!

Good on ya, Terry~!
(I guess others might have mentioned it before, but "DUH! on me.")

[howier6]

2006 26M w/ suzuki DF 50hp
full ballast 300# crew ,7 gals fuel,4 gals H2O
5,000 rpm max
seems like engine sucking air on turns and also when seas are not like glass.
Engine installer says its a recommended suzuki prop. Engine is mounted one hole up from lowest setting. I dont know the dia or pitch ,its a 3 blade Suzuki.
I can't get anywhere close to the advertised 22-24 mph. mine barely hits 10-11 mph and max rpm 5k/ Any suggestions on a suzuki prop for this setup? I have been waiting for the rain to let up and I can get the info from the "stock" prop

[ronacarme]

My 2001 X originally ran a 9.9 Evinrude HT 4 stroke and now runs a 9.9 Honda HT, both with the extra long (25") shaft, which locates the cav plate well below transom bottom. Result is no ventilation even punching into 3-4' waves in a headwind.
However, the 9.9's will presumably not push the X beyond hullspeed (7.4 mph) whether the shaft length is 20 or 25, so the extra drag of the 25" shaft degrades top speed little or none with a 9.9.
Granted that the greater drag of a 25" shaft on a 50+ hp motor may slow the boat in calm conditions (and ignoring the extra cost or possible unavailability of a 25" leg), a 25" shaft may reduce ventilation in rough conditions ( where ventilation may be most aggravating, or even dangerous).
My 2 cents .
Ron

[Robert]

howier6,

2006 26M w/ suzuki DF 50hp
full ballast 300# crew ,7 gals fuel,4 gals H2O
5,000 rpm max

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Your Suzuki DF50 is way overloaded at 5000 rpm maximum. The required WOT RPM range is 5900 to 6500 RPM.
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I think you have the default 13 pitch prop that comes with most 50hp outboards typically installed on 500lb. Jon Boats. You need a 9 pitch prop with 4 blades and or cupping and to mount you motor as low as it will go to prevent the prop catching air.
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You might try a cavitation plate mounted hydrofoil to help prevent the prop catching air. Make sure to select a foil that says it will help with this particular problem.
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I have not heard of anyone trying a prop surround nozzle on the Mac26 to prevent the prop sucking air. But if you are only getting 11mph, I don't think the prop surround drag would effect you much. And there is a chance that it will help with the sucking air problem. If you try one of these please report your results measure before and after the changes you make.
http://www.solas.com.au/propguards.asp

[Mark Karagianis]

howier6, there is admittedly a lot of information in this post, now that it has reached 7 pages. But I think that you are able to read it all, you will find all of your questions answered about props for your Suzi.

And I agree with Robert, you've almost certainly got the default 13-pitch prop that so many Macs with DF-50s were sold with. That is exactly what started me on this quest (!) to maximize the equipment that I had.

Get a new prop - Michigan 3x12x10 and then try powering without ballast (with less than 3 crew who are aware that the boat may capsize if they all go up on the foredeck). This one worked well out of the box yielding 15 -15.5 kts empty (with 3 crew and full fuel tanks) at 6,300 rpm.

Good luck, Mark

[Carioca]

After several tries at pitch/brands, I went with factory 12' / 9 pitch on my Yamaha df 50 .

gps says 19 mph, with peaks at 21.
5500 rpm

[Mark Karagianis]

At the end of the second outing, as we were entering the Marina Del Rey Channel after dropping sails, I goosed the throttle to avoid another boat making a u-turn. Rpms went up to 6,600 but speed didn't increase proportionately. The rest of the way in at low rpm, no problem.

We subsequently used the engine during a a short sail a couple of weeks ago, and the prop behaved differently. Instead of 15 kts at 6,100 rpm, I did 12-13 kts at 6,600 rpm. Fuel economy went down. Really strange, like a different prop had been installed.

Mike (aya16) just borrowed this from me last weekend to tow (2003 Mac with Suzuki DF-50 - until he can afford a 90 HP!) his dingy to Catalina, and reported that at rpm over 5,000 the prop would seem to spin out to redline. He couldn't wait to take it off when he arrived, good thing that he carried a spare for the trip back.

If a prop hub was spinning / slipping, wouldn't it do it all of the time? Wouldn't there be noise? I had really cranked it down before the last trip, thinking that it might not be tight enough. Made no difference.

I'm sending it back to the propeller shop to see what they can find.

[shehzad]

I had been going through this thread but I am unable to understand, what is the difference between a normal propellar which comes with motor and SOLAS propellar ?

I am having Yamaha FT50, which came with a 14'' dia and 11 pitch propellar.
I have completed only 40 hours but I am never able to acheive speed more than 15 mph on my GPS. Indeed, this is without water blast and only three persons on board with very limited gears.
In the first ten hours of my engine, I was acheiving 6000 RPM but after that I am unable to get more than 5500 RPM. I had also changed the propellar to a brand new for the same size as before, but there is very little improvement.
Could I get more speed if I change to SOLAS propellar ?

I shall be very gratefull for a solution, as we often have to pull banana type inflatable boat for my children, beside my sailing.

[Robert]

shehzad, a lower pitch propeller with larger blades will help you get higher RPMs and higher speed since it will be a better match to your needs. Others have used a 14" dia and 10 pitch propeller with the Yamaha FT50 on their Mac26.
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Solas is just a brand name. Michigan Wheel and Piranha Propellers are other brand names.
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Contact a prop dealer and tell them that you are pushing a large boat and towing another boat. Tell them you are not getting high enough RPMs with your 14x10 pitch prop. Then ask them for the prop they recommend for highest thrust. This will be similar to the prop they would recommend for pushing a large pontoon house boat.
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http://www.solas.com.au/
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http://www.miwheel.com/
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http://www.piranha.com/
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Also, if they have a 4 blade prop at 14" diameter and 9 pitch I think it would work very well for you. Going from 3 blades to 4 blades is like going up in pitch, so you can go down in pitch with the 4 blade prop. So, in my opinion, the FT50 will be matched to the Mac26X with either a 3blade 14"dia 10 pitch prop or a 4blade 14" 9 pitch prop.

[shehzad]

Thank you very much for your kind advises.

I only wish to match the speed of 22 mph with others, who have same engine as mine with same propellar as mine. This is what I had come to know from different threads of this forum.

I am having 2006 macgregor 26 M in blue . My problem is that I cannot find any propellar dealer in my area as I am in Pakistan. There are only three macgregors in the country.
It had been very pitty that with new boat and new engine, I could not acheive more than 15 mph, where as others could do.

I shall be very glad to know the solution, if some one could advise.