Hunter 40.5 two blade prop broke in half! Need new one.

Sep 27, 2011
71
Hunter 40.5 Long beach CA - Manly Australia
Hey guys.

I went out in my boat to watch the start of the Brisbane to Gladstone yacht race. Funny thing happened just as I got out of the marina. Gave it full stick as I normally do for a couple min to clear out the engine and blast crap off the prop. Got huge vibrations. Checked the shaft from inside and saw it was wobbling a lot.

I dived into the murky water with no mask (took all the dive gear off to clean it). Seems now I have a single blade prop! Yup. One blade is gone.

I can understand this happening with a folder/feathing but mine is fixed (or was) a fixed 2 blade. Oh well good excuse to upgrade. Pushed the boat out with the dink for an hour or 2 until the wind picked up. Managed to birth it ok somehow later...

I have a yanmar and boat is 1992. What info do I need to know when ordering a prop? Can I find this out without hauling my boat? What specs do I need to know when buying a prop? I know the shaft is 1". Something about taper?

Engine: 4JH2E_YANMAR

Gearbox: 5864_APMD
KM4A_KANZAKI Anyone know the ratio?
 

splax

.
Nov 12, 2012
692
Hunter 34 Portsmouth
Sorry about your propeller failure. The transmission ratio should be on a plate on the rear of the transmission, under the model number(?).
I would go to a three blade propeller if I were in your situation.
 
Last edited:
Sep 27, 2011
71
Hunter 40.5 Long beach CA - Manly Australia
Thanks. Should have had a look when I was there.

Whats the stock diameter and pitch of the prop?

I found the performance very good under motor. With clean bottom and prop I could get 5K at about 1700rpm using 1.8L per hour (less than half an gallon per hour). Top speed was 8K. For me sailing performance and fuel economy is what matters.

What do you think of this http://www.defender.com/product.jsp?path=-1|311|53222|292327&id=85298
 
Jan 22, 2008
1,654
Hunter 34 Alameda CA
Usually the pitch and diameter is stamped into the hub of the prop. A prop shop , or even a machine shop can determine the taper from the hub of the prop. In fact, you can measure the diameter of the two sides of the prop hub and the length. With that info you should be able to determine the taper.

Good luck.
 

Rick D

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Jun 14, 2008
7,132
Hunter Legend 40.5 Shoreline Marina Long Beach CA
I Have Mine...

Dennis, I have my old two blade at home and will check it in a couple of days for the info you need. In fact, if we can figure out how to get it there for less than a new prop there, it's yours. However, if I were in your shoes, I'd bite the bullet and put on a folder or feathering prop.
 
Sep 27, 2011
71
Hunter 40.5 Long beach CA - Manly Australia
Thanks guys! Rick that would be awesome. I will weigh up the prices and if its affordable I want a folder, if not I will just get your old one if it works out. Does anyone know if there are different shafts on hunter 40.5s just to make sure Ricks measurements will be relevant?

Seems you can get non geared Martec for $850 in the usa. If you scroll down you can get a martec stainless steel SLIPSTREAM for double the price. Is that the same as your prop?

http://search.defender.com/search.a...OPTJ_&SI=20c203b3-efd5-439d-a7a9-ef9d5177f2bb

Also does the Yanmar engine have a zinc in it somewhere? I think I better change it. I am worried about what caused my prop to break.

Last time I checked a couple of months ago I still had a fair bit if shaft zinc left. Not sure if there is any left now. My marina is full of box jelly fish and I dont really want to go for a swim in there! I desperately need a haul out but I am waiting on a pending insurance issue which requires a haul out and it has been dragging out.
 

splax

.
Nov 12, 2012
692
Hunter 34 Portsmouth
transmission and propeller

ebay lists a KM4A transmission with a 3:30:1 ratio, another site says 2.63, and another says 2.01... You really need to look at yours.
 
Sep 27, 2011
71
Hunter 40.5 Long beach CA - Manly Australia
Absolutely. I will go take a look next time.

I thought that maybe someone with the same boat as me might also know, so it might be worth asking anyway.
 

Rick D

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Jun 14, 2008
7,132
Hunter Legend 40.5 Shoreline Marina Long Beach CA
Dennis, our specifications should be the same. There are no internal zincs on the engine nor exchanger. The problem may have been lack of zincs in the slip by the PO or there could be some DC leakage which would not surprise me given all the electrical customizations to your boat. There are ways to check that. You should search the forums on this site. OTOH, since you are electrically certified, you probably already know.
 

Dave Groshong

SBO Staff
Staff member
Jan 25, 2007
1,864
Catalina 22 Seattle
Most Hunters have 2.62 reduction, I will find out Monday the original spec and get back with 2 and 3 blade pricing.
 
Sep 27, 2011
71
Hunter 40.5 Long beach CA - Manly Australia
Thanks. Which props can you provide pricing for?
 
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Feb 10, 2004
3,919
Hunter 40.5 Warwick, RI
Denisail-

My 1997 h40.5 has a 1.25" shaft. I have a Volvo 50hp, same power rating as the Yanmar I think, so the prop shaft should be the same size. But you should check. The shaft size is also stamped into the hub of your one-blade prop........

I would urge you to determine why your prop failed before you install another one that may go to the same fate.
 
Sep 27, 2011
71
Hunter 40.5 Long beach CA - Manly Australia
Yeah I hope my shaft is OK. It certainly had a huge vibration and wobble going. But I guess that is to be expected with a one blade prop. I hope the cutlass bearing etc is all OK. It is fairly new. I think it probably suffered electrolysis.

I am very disappointed (but not surprised) that somehow its possible for Americans to get an AU made slipstream prop shipped and fitted $700 less than what it is for me to buy just the prop on its own in AU.
 
Jun 6, 2006
6,990
currently boatless wishing Harrington Harbor North, MD
If memory serves my 40.5 1993 two blade is a 16/12 (diameter/pitch) Pretty sure on the 16 not so sure on the 12.
 
Jun 13, 2004
90
Hunter 40.5 Hampton,Virginia
The two blade prop off Island Girl is a Martec 18" dia X 15 pitch. I have the same engine and being a 1993 I assume the transmission should be the same. I replaced the two blade with a three blade and have never been sorry.
 

Rick D

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Jun 14, 2008
7,132
Hunter Legend 40.5 Shoreline Marina Long Beach CA
My Prop Spec's

Dennis, my factory prop is a two blade Martec 18" X 15 pitch X 1 1/4" shaft RH rotation.

The Slipstream two blade geared folding prop I replaced it with is 19" X 13 pitch X 1 1/4 shaft RH rotation. Note: it is slightly over-propped. I lost 400 RPM. I suggest discussing with your prop provider.

I will PM you re: shipping on the prop.

Rick D.
 
Sep 27, 2011
71
Hunter 40.5 Long beach CA - Manly Australia
Thanks Rick. Was your original martec fixed blade? That's bigger than I thought and your slipstream prop is much bigger than the 16x10 SeaHawk reccomened for me. However they went with a 2.14 ratio.

If the ratio is indeed 2.6 I guess the prop would be bigger. In fact a prop calc spreadsheet found on the net suggests a 19 x 13 with a 2.6 ratio.

I think that you will have less revs/noise and less fuel consumption with your prop if you dont mind loss of top speed. And I guess you have to never run full throttle or it may overload your engine. Thats fine for my motoring style where I am happy to chug at 5K using the least amount of fuel possible.
 

Rick D

.
Jun 14, 2008
7,132
Hunter Legend 40.5 Shoreline Marina Long Beach CA
Thanks Rick. Was your original martec fixed blade? That's bigger than I thought and your slipstream prop is much bigger than the 16x10 SeaHawk reccomened for me. However they went with a 2.14 ratio.

If the ratio is indeed 2.6 I guess the prop would be bigger. In fact a prop calc spreadsheet found on the net suggests a 19 x 13 with a 2.6 ratio.

I think that you will have less revs/noise and less fuel consumption with your prop if you dont mind loss of top speed. And I guess you have to never run full throttle or it may overload your engine. Thats fine for my motoring style where I am happy to chug at 5K using the least amount of fuel possible.
Yes, the original Martec factory two blade is fixed. I lost about .4 knots. I also cannot run WOT for long without the Yanmar overloading. I typically run at 2600-2800 RPM. With the original fixed, I ran 2800-3200 cruising. Martec offered to grind down the Slipstream, but Yanmar said it was OK... barely.