ZIP Prop

Outboard designs up to 14'

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gdcarpenter
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Joined: Tue May 05, 2009 12:18 pm
Location: Raleigh, North Carolina

ZIP Prop

Post by gdcarpenter »

Looking for suggestions/opinions from expertise/experience here.

ZIP with 1959 Mercury Mark35A. Started with 2 blade, 13 pitch aluminum prop - about 27/28 MPH @ 4,200 RPM @ WOT (Wide Open Throttle), pin 1 or 2 holes up. Fully loaded for days outing with 6-7 gallons of fuel she weighs in at 800 lb.

Shifted full size battery and fuel tank to under motor well was able to drop pin to lowest hole. Now have run 2 blade aluminum 11 pitch prop, got RPM up about to about 4,600/4,700 Rpm, virtually identical top end speed. Compression great and throttle plates are wide open at full throttle so it seems engine is working less to push boat with 11 pitch prop. Same speed with 1 or 2 on board.

Thoughts on trying to get and try 3 blade 10 pitch prop? Wondering if the extra weight of brass 3 blade prop could adversely affect engine wear/load or if it would let engine run closer to WOT RPM range around 5,200 RPM and perhaps squeak out another MPH or 2, though I am more than satisfied with her performance for a 54 year old engine.

Photo is ZIP ZIP HOORAY at the summer cottage in Northern Ontario recently, She spent almost a month in the water there and got some real use where she was designed to be. Thanks
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This is my first, last and only boat build.

http://www.gdzipbuild.blogspot.com

Moeregaard
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Location: Thousand Oaks, California

Re: ZIP Prop

Post by Moeregaard »

We're currently running a 10"-pitch, two-blade aluminum prop on our Mark 55. Our Zip is probably on of the lighter ones and we typically see 30 MPH @ 5600 RPM. Old Mercs like to wind up, so it's better to be a little under-propped than over. Your numbers with the 13" prop reflect ours with that same blade. I also have a three-blade brass prop with 10" pitch, and it's a really nice compromise when we have a few more folks in the boat. I should mention that our motor has the fixed-jet carbs from a 35A, and I'm told that this reduces our top end slightly, so we're probably very close in HP to your Mark 35A. With your intended use I think you and your Merc would be happier with the 10" three-blade prop.

-Mark Shipley
A boat is just a wooden box with no right angles.

Mike Sea
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Location: North Canton, Ohio

Re: ZIP Prop

Post by Mike Sea »

I also think you should try a 10 or 9 pitch prop and check the revs, that motor should tack out at 5200 to 5600 rpm. I have seen speeds of 35.4 mph with a 10.75 x 13 Mercury prop and a Merc 300 on a smaller boat similar to the Flying Saucer but I had too big a prop, should have tried a 11 or 12 pitch.
Personally I would not have any problem running a brass prop. The main problem with damaging the lower unit is normally how you shift. Shifts should be main at recommended rpm and and very firm, too many people want to ease the motor into gear and this causes wear on the gears.

Mike

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vupilot
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Re: ZIP Prop

Post by vupilot »

What a beautiful boat and setting.

Im running a 10-3/8x13 3-blade aluminum prop on my 1975 40 hp Mercury. 5500-5600 rpm WOT 30MPh with 2 people on board.

gdcarpenter
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Joined: Tue May 05, 2009 12:18 pm
Location: Raleigh, North Carolina

Re: ZIP Prop

Post by gdcarpenter »

Thanks all, starting search for alternate prop, just want boat performance to be all it can/should be.

Have lead on 3 blade prop but can't find Merc No. in the charts I can find.

48-22575A2. (The A2 suffix is usually used to indicate a fit for 35A models)

Any confirm that this would or wouldn't fit my Mark35A appreciated.

Would a prop for a 55A or the350-400 series fit the 35A, same 11 spline?

My thinking is that since going from a 2 blade 13 pitch to a 2 blade 11 pitch gained me RPM but NOT MPH, that going to a lower pitch 2 blade would not likely gain me any more MPH either, so I'm looking for a 3 blade 10 pitch, which is only 10" diameter vs. 10 3/4" for a 2 blade. Logical?

Seems prop selection is more art/guessing than science. Thanks again for your real world comparisons and feedback. Would like to hear that 35A humming over 5,000 rPM at WOT since it sounds more at ease at the higher RPM's.
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This is my first, last and only boat build.

http://www.gdzipbuild.blogspot.com

gdcarpenter
Posts: 1382
Joined: Tue May 05, 2009 12:18 pm
Location: Raleigh, North Carolina

Re: ZIP Prop

Post by gdcarpenter »

Thanks all, starting search for alternate prop, just want boat performance to be all it can/should be.

Have lead on 3 blade prop but can't find Merc No. in the charts I can find.

48-22575A2. (The A2 suffix is usually used to indicate a fit for 35A models)

Any confirm that this would or wouldn't fit my Mark35A appreciated.

Would a prop for a 55A or the350-400 series fit the 35A, same 11 spline?

My thinking is that since going from a 2 blade 13 pitch to a 2 blade 11 pitch gained me RPM but NOT MPH, that going to a lower pitch 2 blade would not likely gain me any more MPH either, so I'm looking for a 3 blade 10 pitch, which is only 10" diameter vs. 10 3/4" for a 2 blade. Logical?

Seems prop selection is more art/guessing than science. Thanks again for your real world comparisons and feedback. Would like to hear that 35A humming over 5,000 rPM at WOT since it sounds more at ease at the higher RPM's.
This is my first, last and only boat build.

http://www.gdzipbuild.blogspot.com

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Roberta
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Re: ZIP Prop

Post by Roberta »

Hey Bill,

My Merc book indicates the A2 as being 11 spline which will fit the 55 and 35A.

A-48-29986A2 is 13" 2 blade Alum

A-48-29296A2 is 11" 2 blade Alum

A-48-29985A2 is 10" 2 blade Alum

A-48-25773-A2 is 9" 2 blade Bronze

Any prop with the "A1" suffix and NOT "A2" is a 14 spline.

A-48-22105A2 is a 10" 3 blade Bronze listed for Mark 58, 58A amd 55A motors

I can't find a 48-22575A2 in my listings.

Hope this helps,

Roberta
Roberta "Queen of the Boat Builders"
Built Zip "Oliver IV", Super Spartan "Jimmy 70", and Torpedo "The Glen L".

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vupilot
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Re: ZIP Prop

Post by vupilot »

You did not gain any MPH going from your 13 pitch to 11 pitch because in general a prop with more twist (pitch) will give the most top speed.

In one revolution a 11" prop is going to travel forward less distance than a 13" prop so in theory you should have lost mph but because you gained rpm you were making more hp and more revolutions of the prop so your mph speed basically stayed the same.

A prop with more pitch will give you more mph at a given rpm until you go too far and lose efficiency. To get the rpms up at WOT you decrease the diameter of the prop.

It sounds to me like your original 13 prop was about right but you just needed less diameter to bring the rpms up.

gdcarpenter
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Location: Raleigh, North Carolina

Re: ZIP Prop

Post by gdcarpenter »

Tanks vupilot. Since smaller diameter 2 blade prop doesn't seem to exist, perhaps the3 blade 10 pitch might do the trick, now to try and find one! :)
This is my first, last and only boat build.

http://www.gdzipbuild.blogspot.com

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vupilot
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Re: ZIP Prop

Post by vupilot »

Whats the diameter of the 2 blade you are using measure?

gdcarpenter
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Re: ZIP Prop

Post by gdcarpenter »

My 2 blades have both been 10 3/4" in diameter, 13" pitch then 11" pitch. Could try a 9 or 10 pitch 10 3/4" diameter prop, but since dropping 2 pitch sizes and keeping the same diameter netted me RPM gain but no MPH gain (which I think I understand), seems another lower pitch with the same diameter would likely get me more RPM with nil MPH again. Hoping the combo of going to a 3 blade with a 10" diameter might gain me a bit of both. Not easy to come by though.
This is my first, last and only boat build.

http://www.gdzipbuild.blogspot.com

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vupilot
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Re: ZIP Prop

Post by vupilot »

Id go with a 10x13. You might only be able to find a 10-1/8 x 13 that fits though. Here is a chart also. http://www.maxrules.com/oldmercs/Propellers/Props/4.pdf

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