Recommended (minimum) Propeller Blade Tip Clearance to Hull

[HighFly_27]

Hello All,

I have a Islander 37 MS and considering a replacement -- 15 1/2 diameter, 3 blade propeller. Currently, is has a 14.5 inch. 3 blade propeller installed. I measured the blade tip clearance to the hull & measured 2.5 inches. I don't have the pitch worked out yet and working with prop. vender to crunch the final numbers.

My Original Question --

What is the Minimum Clearance that's Acceptable to Run in Ref. to the Hull. I have 2 1/2 inch clearance with the 14.5" prop. .

I have read a number of the reviews on -- feathering props. i.e. Gori, Autoprop and others. I'm looking for a Prop. that holds up. I'm open to recommendations for a Bullet Proof Propeller.

Thanks in Advance,

Avery

[GordMay]

Greetings and welcome aboard the CF, Avery.

Your prop’ clearance should be 15% of the prop’ diameter: so
2.175" @ 14.5" dia, or
2.325" @ 15.5" dia.
You'd only have 2" clearance with a 15.5" dia. prop'.

➥ Propeller Clearance Diagram - Cruisers & Sailing Photo Gallery

[HighFly_27]

GordMay & All,

Thanks for the Information on the Min. Clearance.

Avery

[HighFly_27]

I just got a quote for a Gori Prop. & Spec'd for my I-37. It's a lot of money... concerned if it will hold up over time.


Does anyone know of a -- Variable Pitch & Feathering Prop. that is (nearly) Bullet Proof ?!?


Avery

[HighFly_27]

[QUOTE=HighFly_27;1809581]I just got a quote for a Gori Prop. & Spec'd for my I-37. It's a lot of money... concerned if it will hold up over time.


Does anyone know of a -- Variable Pitch & Feathering Prop. that is (nearly) Bullet Proof ?!?


Avery[Live Life to the Fullest, Waiting for Tomorrow May be a Little Too Late/QUOTE]

[Cheechako]

Max Prop.
BTW, very cool boat, almost bought one a couple years ago. Love the raised salon setup. Yours a 4-108?

[HighFly_27]

Cheeckaco & All,

Yes, Perkins 4-108 M and just rebuilt with about 50 hours since complete rebuild. It has a Velvet Drive (rebuilt) Borg Warner 1.5 : 1 gear box. I need to find the correct prop. for it and I'm all set.

I ain't rich and can't afford to make a mistake on the propeller I buy. I have read some horror stories about feathering/ variable pitch prop's.

So, I asking folks about .. what props. are Trouble Free and Last & Last.

Avery

[Cheechako]

Well... the Max Prop aint cheap but it's been proven for decades. I prefer feathering and I'm a little leary of folding props myself, but that's probably based on the old style early ones.
In reality, a folding/feathering prop will only make a small bit of difference in light air sailing. You could just go with a 3 blade fixed if you want to save a couple thousand dollars.
In real sailing conditions your boat will reach hull speed with or without a feathering prop.
Having said that, I've had 5 Maxprops over the years... sometimes we just have to have things. But looking back... that's probably $15000! I hope I got to my destinations a lot faster!!!

[Nicholson58]

Originally Posted by HighFly_27

I just got a quote for a Gori Prop. & Spec'd for my I-37. It's a lot of money... concerned if it will hold up over time.


Does anyone know of a -- Variable Pitch & Feathering Prop. that is (nearly) Bullet Proof ?!?


Avery

We have a Hundested prop with pitch control by hand crank from the cockpit. 24-inch; 3-blade. It is 1984 vintage and zero problems. This is the very simplest version with no integrated electronic controls. It is really nice on our very heavy boat to be able to load the engine according to sea state & wind/sails. We are 36 tons with 115 HP 6-cyl Westerbeke. We only turn 1200 engine rpm with 2:1 reduction. At his rpm we motor-sail in light winds. Pulling out from a dead stop or towing, we pitch low for high thrust. They are not cheap and there may not be a solution small enough for your boat. The benefits are not so big on small & light vessels. As the mass & drag goes up, so do the fuel savings.

https://www.youtube.com/watch?v=v0M8UuZ8y1c

Hundested Propeller | Supplier to the marine trade for over 90 years

http://svseeker.com/controllable_pitch_propeller.htm This is the full auto system. Ours is manual hand crank. We balance the rpm & exhaust temperature to keep below 195 - 200 F using the throttle setting.

[HighFly_27]

Cheeckaco, Nicholson58 & All,

1st, Thanks for Your Input, Good Information.


Cheeckaco, I see that -- Maxprop's have served you well over the years.

Nicholson58, My Oh My, what a Propeller the Hundested Prop. is but not applicable for my I-37.

I just bought a -- Hydralign, Model A, 14 in. Dia. for my I-37. I read all I could about all the Propellers that would be A Ok for my I-37. I sent all my I-37 Spec. Data out to two different propeller venders and came back with -- 14 inches, with 9 or 10 degrees pitch.

I've researched the Hydralign Propeller and like the robust design. It appears to be heavy duty in the hub area & built like a tank. The thick hub may be a little too big and may down grade the efficiency of the propeller. I'm guessing about the loss of efficiency due to a large hub. I'm a retired FAA Mech. and have seen older design prop's. on airplanes with big hubs... they were not as efficient as the newer (smaller) hub designs. However, if the Hydralign is Tough and Stands Up (bullet proof) I'd be Ok with a lost of efficiency.

You will see, my pending Post, looking for Hydralign Owners, and they're comments about the good and bad on their Hydralign Propeller.

Thanks,

Avery