another, prob dumb, prop question Honda 50

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Re: another, prob dumb, prop question Honda 50

Post by BOAT » Thu Aug 18, 2016 12:19 pm

I get a tiny bit of a singing sound on my three blade at very very low RPM but only in dead calm SHALLOW water and you can only hear it if you are standing in the cabin about in the middle of the floor (like when I am slowly motoring in the harbor). I think it's cool and it's hard to find just the right RPM to make it happen - it's not always.

Does the 4 blade on make a real loud sing sound? I guess that might be pretty annoying after a while.

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Re: another, prob dumb, prop question Honda 50

Post by Whipsyjac » Fri Aug 19, 2016 8:23 am

A note about my props:

The ones that came with the Whipsyjac (1996 fairly stock :macx: ) aren't worth discussing at about 50% slip.

I'm running a 1996 Mercury 50hp 4-stroke ELPT carburated motor NOT BIGFOOT (1.83:1gears) with a recommended WOT rpm range of between 5500 and 6000

The michigan wheel Vortex 4 blade had amazing acceleration, and great reverse thrust for docking and maneuvering. It wouldn't rev past 4,900 and only gave me 14kts at the very best(like once). It ventilated easily(I was considering lowering the motor on the transom) and I often had to switch to one of the little blender blades my boat came with.

In 2015 I got a Michigan wheel Large Area 3 blade(elephant ear) Vortex 12-1/4"diameter 9 pitch(largest diameter I can run) 992601. With a light to medium load and my mast up it consistently put us over 15kts and had good acceleration and good reverse thrust. First weekend out it seemed to run at 5900-6000rpm@WOT. This year lightly loaded and no mast it was revving 6300 at 16kts and as I've experienced before that is just at the rev limiter.

This spring 2016 I went up 2 inches of pitch(as per usual recommended spread on props). I thought I'd have a prop for light loads and a prop for heavy loads. I bought the same series Mi Wheel but as you increase the pitch in the series the diameter drops slightly it is Mi Vortex 992603 11-5/8"dia x 11" pitch. It reaches 5400rpm with 2 aboard 5500 with me alone no mast and 5000-5100 with the cockpit full of adults. Top speed with no rig,2 people, medium load: 16kts, me alone: 17.5kts(I'm aware of and filtering out the effects of current) I hit 21kts in Active Pass running with the current.

I could have the 9pitch tweaked at the prop shop or I could by another prop the 99602 which is in between the two in dia and pitch. This would keep from changing props in all but the most extreme circumstances. I would probably keep the 99603 for more fuel efficiency when cruising below hull speed( I think I would test that theory first).

I think the 4 blade was made in USA but the 3 blades are made in Korea. The interchangeable hub slid out of the 4blade easily but does not come out of the 3 blade props without a perfectly matched socket driven by a 2lb hammer. I would definitely get another hub kit(just the rubber insert if Ican) to make sure prop changes go smoothly.

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