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I have a 31' 1983 Seahawk (Sim. to a Scarab of that time) it has 2-525 hp Pfaff motors w/ Arneson drives 1.32 gear ratio.
I have two sets of props 23 x 16* that go's 68 @ 5600 RPM & 27 x 17* that go's 65 @ 4800, both are 3 blade cleavers. With the 27 x 17* the boat wants to lean to the side a little and feels loose / unstable when turning at a lower speed. It seems that the boat should go faster and handle better. What could I do to one of these props to achieve something like 71 MPH @ 5200 with better handling.

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I'm assuming the props with the listing problem are 17" diameter and 27 pitch? The boat doesn't want the 17" diameter. Who made the props? I have some ideas. Call us so we can discuss it further.

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Here is a photo of the 17" dia. the 16" dia has the word "record" ingraved on the hub.

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Can you tell me what is engraved in the 17" hub. We most likely can rework these to get the rpm you need and improve the handling and top speed.

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After looking at the picture again they look to have been worked on before but are still in box stock condition. Hard to tell from a picture.

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no engraving on the 17"

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I see some stamping on the hub. Does it only say

17x27

or are there other letters and numbers?

We should talk more. Call us if you have a chance.

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yes, 17x27 no other markings

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do you think that the 17 need to be cut down to a 15 1/2"

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No that's too much.

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Brett, after talking with you yesterday about my 26% prop slip I called Howard Arneson to find out how I could get more bow lift. He said maybe that was not the problem and that he thought that the drives were trimmed to high allowing the props to slip more they should. After talking with him I picked up a power boat mag. to check prop slip on tested boats. I seemed to me that the bravo style drive/ prop had 10-12% slip like you said, but what was interesting was that all cleaver/ surface type props had 21% slip or more. Why is this? maybe I am not that far off w/ 15.5* instead of 17*

Thanks, Phil

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Howards drives are designed to run on the surface. They are awsome drives They are great for boats that fly on their own. High slip on a boat running triple digits at 6500rpm is one thing. On a deep V like yours running 70 it is another. All surfacing cleavers do not run at 20% slip. Not hardly.

As we discussed and you stated, the bow wants to take control and steer the boat. The only way for you to get speed and control was to over trim the boat. OK, trim the drives back down as suggested by Howard. How is the drivability and slip percentage now? We know it gets worse. Yes it would be better to leave the drives in the water. Problem is, the bow stays planted. You need the stern planted.

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Thanks Brett. I am starting to understand a little bit more how it all works.

Phil