I’m pretty close to actually owning Popcorn, the NS33 for sale in Alameda. I finally got through the surveys earlier this week and got the report last night. The basic boat - hull, deck, engine, interior joinery&fabrics, mast, sail - are in very nice condition. The boat has not been used for quite a while and there are quite a few operational things to sort out. Sticking valves, accessories that don’t work, etc. There are also a couple of big problems. One of those is the prop. It is a 2-blade bronze folding prop and it is so worn and loose that the blades are totally wobbly. So much so that the boat shudders violently when put in gear at the dock and there is still quite a bit of vibration when not tied up and free to move. According to the yard owner, it is too worn to repair. There’s not enough meat left in the bronze to bore out and install larger diameter pins. So we will need a new prop.
As I was learning about this I was surrounded by a yard owner, a surveyor, and a professional racing sailor. They all agreed that if I was going to put on another folding prop, a Gori three-bladed one would be the way to go because the “overdrive” is better for cruising boats. I have no idea how often that will matter to me, but I’d be interested in you all’s opinions.
But here’s the really big question if I get the Gori: what diameter and what pitch? The current 2-blade prop is 18" diameter by tape measure, but it was either never marked or the markings are inside of it, so we have no idea what the pitch is. And it seems like pitch and maybe diameter as well would be different when comparing two and three bladed props.
Does anyone have an NS33 with a three bladed Gori prop? If so, what do you recommend for diameter and pitch? If nobody has that prop I would still be interested in the specs of any prop on an NS33.
Brian,
The prop has to be matched to the engine and transmission reduction ratio as well as the hull. If you are getting info from another owner make they have the same setup. My brother and I both own 1982 26s with Beta 20 hp engines. We both installed the same dia Maxprop but we have to have them set to different pitches because his transmission has a 2.4:1 while mine is a 2:1 reduction ratio. The Maxprop has adjustable pitch which is nice but the props are expensive and the blades are not as efficient as some of the other designs.
I considered a 3 blade Gori because of the over drive but a local yard told me that the silt in the water in our area destroys the rubber bump stops in about 1 season. The prop has to be disassembled to change the bumpers and the parts are over $100 Cdn. The two blade Gori does not have the stops but it does not come with the over drive.
The prop dealers are usually the best source of info on the correct size of prop. Check with the dealer but I believe most of them will exchange the prop if they recommend the wrong size. Conditions will apply.
Flexofold makes a nice prop at a reasonable price so you may want to investigate them.
They are the dealer. I spoke to him several times about a Gori Propeller. I ended up buying a used gori 2 blade for our 26 but i almost bout the 3 blade new. These guys are very helpful and can walk you through what you need. They will likely have an early order discount on right now as well!
I was able to buy new pins from Geof at AB Marine and had a local machine shop re-bush the blades. My total cost is about one boat buck. I’m actually re-installing it today.
Joe Valinoti
S/V iL Gatto NS30U #221
Sea Harbour YC
Oriental, NC USA
Attached are the specs and 2020 invoice for a 3 blade Kiwi Feather prop.
As indicated this was for a Universal M35 with 2.13 reduction gear.
I took a chance on it as it was relatively inexpensive. In 2020 $1500 delivered. The propeller worked out well with no troubles.
When I replaced the engine last year, we modified the propeller with new blades to match the new engine’s characteristics. That change was half a boat buck.
US distributor is Daniel Gleich in Marina Del Rey, CA
For what it’s worth, l have a Michigan Wheel fixed 3 blade propeller connected to a 1995 Yanmar 50hp JH2E engine and corresponding transmission, which I am very happy with. (The NS 354 is the same hull size as the NS 33)
If you expand the photo, you can see it is a bronze Michigan Wheel MP 17” RH 14 pitch. Deep Blue Yacht Supply has them for $561.
At WOT, the engine maxes out at 3700 RPM, which is slightly above the recommended 3600, but well within Yanmar engine specs.
My diver spent three hours polishing it to a jewel finish when the boat was out last year for bottom painting.
I have the Maxiprop Easy, expensive but the pitch is adjustable without having 3 hands as required by the standard maxi.
I did hav a Kiwi prop but the westerbeke 21 I had at the time did not have enough power in reverse. The transmission would lock up. Very exciting when docking.
Some people like the Campbell Sailors Prop. Mainesail from Marinehowto did a test on boat owners.com and thought the Campbell prop reduced drag. It is inexpensive and requires no service except cleaning.
You want to work with a vendor who can help you select the prop for your boat and will stand behind their advice.
Can you get your M35 and Campbell prop to produce 3200 RPM at full throttle.
You need a photo tachometer in the crankshaft pulley to verify the RPM. If you can achieve 3200 RPM, you might be able increase the prop. If you can’t get to 3200 ROM at full throttle, your prop is already too aggressive.
Expect your engine tachometer to be reporting inaccurate RPM as it is likely not correctly calibrated.
Your current situation RPM/speed might be confounded by tachometer inaccuracy.
A photo tachometer can be found online at low dollars.
Rick,
2400 is 75% of max rpm and well within the recommended cruising rpm.Practical Sailor suggests 60 to 80%.
Hull speed on the 30 is around 7.2 knots. The general practice is to size and pitch the prop so that you can hit the max rated engine rpm and that the max rpm coincides with hull speed. In theory you would want to hit 3200 rpm as you speed through the water, is about 7 knots. The hull and prop need to be clean, no waves and no wind.
With your current setup can you hit 3200 rpm and if so at what speed does that occur? The numbers you have given suggest you are getting about 1 knot per 500 rpm. If I assume 5 knots is 2200 rpm, 3200 would translate to 7.27 knots. This suggest the current pitch and size are correct. Assuming 5 knots at 2400 rpm, 6 knots would be 2880, close to what Joe gets. I can’t remember which engine Joe has.
If you are getting 5 knots at 2400 rpm it would get you 6.6 knots at 3200 which would seem to be under pitched.
