Auto Prop vs. Standard 3 Blade Fix Prop

[Gordon Myers]

Had Passage 42, buying a 450. Considering an Auto Prop. Does anyone have comparison numbers (rpm vs. speed) between the standard 3 plade prop and Auto Prop. Also any experance under sail.

 

[Bryce Grefe]

autoprop

I have an H410 which I installed an Autoprop this summer. I replaced the factory 2 blade prop. The increase in performance was incredible. At 2000 rpm, the boat speed increased by 1-1.5 knots. I'm assuming fuel economy increase proportionately. Acceleration and back down are equally awesome. The boat will turn inside itself. Under sail the shaft needs to be locked (put it reverse) to feather the prop. The only item that took some adjusting to was slowing the boat. At an idle the boat will maintain 2-2.5 knots and nothing less. To slow the boat you have two options. Put the boat in neutral, and the prop will act as a drogue and quickly slow the boat. Alternatively, shift to reverse and give the engine a "burst" of rpm to change the prop to reverse pitch. If you don't goose the engine, the prop takes a while to reverse directions. Once I compensated for this, it's made pulling into a slip or onto a mooring a dream. Additionally, one can actually control and steer the boat in reverse. I feel its been a great investment with a dramatic increase in performance.S/V SpellbinderWeymouth, MA

 

[Chuck Vincent]

Didn't Work!

I went through 3 AutoProps, but the vibration was going to break apart my drive train. I know the AutoProps work well on some boats, not so well on some, and on some you can get them to run without vibration. My Passage 42 was one it will not work on.I went to the MaxProp.Chuck VincentEagle's Nest II

 

[Chuck Wolfe]

Autoprop and RPM's

Don't pay attention to RPM's with an Autoprop. When you get the prop you tie down good at the dock, put it in forward and see what your max rpm's are. If they are close to the factory spec, then you are okay. After that, you just accelerate until you get close to hull speed. On my boat, it is with one heck of a lot less throttle than before. If you give it more throttle, the rpm's won't increase but you'll start getting black smoke because you are overloading the engine. I had a vibration originally but it seems to have gone away. Autoprop will take the prop back if it doesn't work for you. They are standard on Baltics and Swans now and you don't have to haul out to repitch them like Maxi-props. And I did confirm with Yanmar that if you are getting white exhaust, you aren't overloading your engine (your heat gauge is another clue). Final conclusion. Great for motor sailing, just plain sailing and backing up.chuckwolfe@mail.com

 

[Bradley Cavedo]

Disagree with Wolfe's Theory

We have the P42. For this engine, 62hp turbo, we must achieve at least 3600 rmp under full throttle in forward, or the prop is too big. Every engine has a rating like this, although the number may be different. Our crusing rpm is 80% of 3600, or 3000 rpm. We actually can reach 3800 so we have a max cruising rpm of 3100. My understanding is that the 80% business is mandatory on the Yanmar engines.