2009 Hunter 33 3YM30 Propeller Size

[carbonrobot]

Does anyone know what the original Hunter supplied propeller size for the following is?
2009 Hunter 33, 3YM30, KM2P-1... 2.21/3.06 ratio forward/reverse
I have a Michigan DJ355, 15R12 installed by the PO, but wanted to know what the original was for reference. Considering an upgrade to a Flexofold (who is recommending a 15x10).

 

[carbonrobot]

Response from "Marlow-Hunter", although I think the max rpm quoted is incorrect.

To preface, the company that built your boat, Hunter Marine, no longer exists as of 2012. We at Marlow-Hunter are building new Marlow-Hunter boats. However, we do attempt to support existing Hunter owners with the information we have available.
16 x 11 RH 2-blade, cruising is 3849 RPM.
Regards,
Joe Kerr

 

[wufibugs]

Since Hunters come with fixed blade props, I suspect that is what you are getting from their support folks. Similarly, the folks at Flexofold have a vested interest in making you happy and themselves money. If the larger more expensive folding prop were ideal, I suspect they'd have recommended that one. Support at Flexofold were correct in setting the size for my H31 with the 2GM20F

 

[carbonrobot]

Thanks for the input, the Hunter rep sent a clarifying email as well.

The continuous RPM is the cruising RPM which is 3489. The 3 blade was optional which had less pitch and diameter. Also the pitch can vary depending on the area of the blades which is also known as DAR but there has not been a spec listed for that. The typical prop was a Michigan Wheel using their sail prop.

 

[druid]

Here's the best propcalc calculator I've found: key in the numbers and it will tell you what prop you need. 15R12 sounds pretty high. I feel getting the RIGHT prop is about the most important part of the whole engine system. You may need to tweak it a bit once you get it. I punched in some numbers that might be close for your boat and got 14R8 (7.7 knots @ 3400 RPM) - you can punch in your own numbers.

Oops, can't upload an .xls file. Maybe do a websearch for propcalc.xls - it's a free program.

druid

 

[gladwish]

Too bad you aren't looking for a Flex o Fold two blade 15R12 for a 1" tapered shaft as I have a brand new one sitting on my shelf for almost 3 years. I bought it for my last Hunter and ended up selling the boat before installing the new prop. The new boat already had an upgraded prop so the Flex o Fold became redundant


Good luck with your prop shopping or if you end up looking for a 15R12 mine is available for a very aggressive price


Andrew

 

[Scott B]

Thanks for the input, the Hunter rep sent a clarifying email as well.

Those numbers are way off!!!!

WOT on the 3YM30 is 3200 - 3400. Cruising speed is 2800 - 3000. I usually run mine at 2600 - 2800 which is the "sweet spot" Anything more and you're just burning diesel and wearing down the motor.

 

[carbonrobot]

According to the Yanmar specs for 3YM30 is 3600 max with a cont rpm of 3489.

We typically cruise at 3200.

Yanmar recommends over-propping by 100-200 RPM to ensure load is achieved. I can upload the relevant pages from the manual.

https://dl.dropboxusercontent.com/u/4795611/3ym30.PDF

 

[seadaddler]

When I got my new 2007 H-36 I new the prop that the dealer installed was not the
right size because of slower speed at max rpm's and black smoke.
I did what you are doing here and also went on the owner list in this forum and sent them all
emails for help for the proper size to make sure.
I have been very happy with my flex o fold since 2008,flex o fold was correct with the size,Ithink the dealer installs the prop and not Hunter.
Nick

 

[Scott B]

It was the original message of cruising at 3849 that threw me off.

Although you can cruise at 3200, I've found over the years that anything much above 2800, 6.5 knots, Vari-prop, fully loaded for cruising and pulling a dinghy, I'm not getting much more speed and only seem to be burning more fuel. If you check the Performance Curves att'd, the HP almost levels off at 2800 and a slight increase at 3200 and starts dropping at 3600.

 

[carbonrobot]

Thats a good observation Scott. Like all things its a give and take. I don't think I'm achieving 6.5kts at 2800RPM but can't honestly remember (I need to keep some better notes this coming year).

It looks like the additional rpm results in ~0.13g/hr more fuel consumption. I know I can achieve full speed at 3200 (7.2knts), so for our cruising, getting to our destination a bit quicker matters more than the extra gallon of fuel to do so.

It's interesting to see how different props affect this as well. A higher pitched prop would give you more speed for a given RPM in theory, but I wonder how that affects fuel consumption.

 

[Ken13559]

carbonroot, I read it as Yanmar recommend "under-prop" so that the engine can reach max rpm. Is that right?

 

[carbonrobot]

Ah, good catch Ken... that actually makes more sense.