MV 34 - 4 blade props

[DickTuschick]

Hi Jim,
Just saw your posting on aqua drives and the sound tiles. I just don't know....we have not tried the 4 blade props on a boat with those options installed so I can't comment. However....logically it would seem that the benefit from the 4 blade props would be at least slightly less, as those options already do reduce the vibration and noise to some degree.

[Tom Green]

I had the aqua drives put on my boat MV 34 99. It has 100 hp engines. The aqua drives made a very big difference. I have been contemplating the four blade props but hesitant not knowing how much more difference it would make. I may try it be able to give some idea of the added benefit. Based on the difference with the aqua drives though, I would recommend them. They are expensive compared to the props though. There are other benefits from the aqua drives though having to do with alignment etc.

[DickTuschick]

Hi Folks,
Now that we are close to receiving the first batch of 4 blade props for the 100 hp engines (75 hp to follow shortly thereafter) Michigan prop has announced that new prices will be in effect for any new orders placed from this date on. As soon as I have the new pricing I will post it.

[jim]

If any of the purchasers of of the four blade props have any before and after decibel data or stories to share about the change-over from the three blade props , many of us would love to here them. jim

[Sno' Dog]

Here they are!
After placing the order with Dick back in December, we finally received our new four-bladed propellers! Hoping to install them soon. Will let you know the results. Stay tuned...
Henry
www.snodoglog.com

[Mishigas]

Henry they will never look that good again I installed my new props today and I splash on Friday. It should be interesting to see the results and changes with these props. Regards, Sandy Kramer MV MISHIGAS

[Sno' Dog]

OK, our four bladed props are on - and we love them! The boat runs noticeably smoother - PLUS, we have gained over a knot in speed! I've just published the test results on SnoDogLog on the Performance page: www.snodoglog.com/Performance.html.
Check it out, we now have a 20-knot powercat!
Henry
www.snodoglog.com

[jim]

Thank you Henry for sharing all the data on the four blade props on the Snodoglog performance page. I'm impressed. One question for Frank on Kama Kat. What made you think the PDQ's performance, noise level and vibrations would improve significantly with the four blade props. Simon Slater obviously knows something about hydrodynamics and props, but didn't switch to them until the last four or five MV34's made. jim

[Sno' Dog]

Hi Jim,
The 3 vs. 4 blade question has been much discussed. Frankly, it remains more of an art than a science. In general terms, more blades mean: more bite, more drag - and more expensive! The cost factor may be one reason that PDQ's were equipped with 3-bladers. But there are many factors to consider. Designers often prefer odd numbers of blades because props operate in a wake field behind the boat - the top blade is loaded the least, the bottom the most. So it's best not to have a blade at the top and bottom at the same time.

But, this is only one of several design considerations. Other things being equal, the individual blades of the 4-blader will be more lightly loaded. This may result in less cavitation and less impact transmitted to the nearby hull sections. In the case of the PDQ, I suspect these factors play an important part in the desirable results we have seen.

No matter how knowledgeable the designer, a certain amount of trial and error is still required to find the best propeller for a given design. There are just too many interrelated factors, along with insufficient modeling data, to make accurate predictions.

Finally, I gotta to say, I was frankly surprised to see the extra speed from our new 4-blade props on Sno' Dog. Apparently, in this situation, they're able to deliver more thrust in (what most power-boaters would call) mid-range speeds. We are thrilled with our new smooth-running, 20-knot powercat!
Henry
www.snodoglog.com

[jim]

Thank you for the explanation, Henry. Jim

[Kama Kat]

Hi Jim,

I discussed the three vs four bladed props for Kama Kat with Simon of PDQ virtually from day one (end of 2003). We had no disagreements on the potential benefits of going to four blades. His arguments for staying with three blades seemed to be two fold; first, it was less expensive and second, "most" boats seemed to be fitted with three bladed props when first out of the shop.
Since the mariners are somewhat conservative, they prefer to repeat successes of old even with new boats .....hence, the "popularity" of the basic three bladed props. Those who are interested in technical details, may look at various propeller books and read the benefits of increasing the number of blades, skewing the blades, etc. Design of individual props. is highly scientific/techincal, the "guess" or "art" of matching a particular prop. to a particular boat/engine combination for varying sea and boat loading conditions requires compromises. Experienced designers, and boaters willing to experiment, will find the preferred choice for a particular boat. I hope I've answered your question Jim.

Safe Cruising,
Frank

[jim]

Hi Frank, Thank you for your input. Fascinating. Jim

[DickTuschick]

Hi Folks, After a month of heavy weather cruising in the Bahams I can report one other benefit from the 4 blade props...significantly less cavitation in rough water. I would guess a 50%+ reduction.

Further news on the subject:
Now that the "bulk purchase" on the props is over, I will no longer be involved and you can now order these props directly from the Distributor, H&H propellor in Salem Mass. The contact there is Jim Blanchard and his phone # is 800-325-0117. ext 3012.
The price for the 100 hp is $770 per prop plus shipping.
The price for the 75 hp is $797 per prop plus shipping.
Lead time is approximately six weeks.

After a couple hundred hours I can definitely say this is one of the best upgrades we have ever done.

[jbrad]

Hi Dick,

Good news to hear about your cruising and the performance of the four blade props. If you remember, we had extrteme "singing" issues with the four blades we tried six years ago. Has that been a significant issue on any of the recent props?

Jimmy
Mr. Busy

[Leadfree]

We are sooooo happy with our 4 bladed props. The boat runs faster, quieter and with less vibration.
Lead Free Too