Converting Mercury Prop to Johnson Outboard Motor

Converting Mercury Prop to Johnson Outboard Motor 13 years 1 week ago #72581

dpanky
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My fastest prop on my now sold 15' Glastron V-153 with a 1974 115 HP Mercury was 53.5 MPH using an old Quicksilver 2-blade bronze prop 21" pitch cupped.

I now have a 16' Glastron/Carlson CVX-16 with a 1985 115 HP Johnson that can go 55.0 MPH GPS with a Raker 22" prop.

But in the quest for speed, I would like to rehub the Quicksilver 15 spline to a Johnson 13 spline and use it on the Johnson.

I know that the forward wall of the Quicksilver prop needs to be turned down to fit inside the Johnson housing. Is it feasable? Are there any special thrust washers and spacer washers needed?

Any other issues?

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Re:Converting Mercury Prop to Johnson Outboard Motor 13 years 5 days ago #72654

Chinewalker Offline Gold Boarder Posts: 548 Karma: 42 Thank you received: 10	I really doubt you would see much of a speed increase by doing the conversion. MUCH easier and cheaper to find a better off-the shelf prop that will fit your Johnson... Check this box to be notified of replies to this topic. Note: BBcode and smileys are still usable.
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Re:Converting Mercury Prop to Johnson Outboard Motor 13 years 4 days ago #72681

dpanky Topic Author Offline Junior Boarder Posts: 109 Karma: 11 Thank you received: 0	The best OMC props so far are the Rakers, but was looking for something faster. We will see what the prop shop says about the feasability and cost of the conversion. Check this box to be notified of replies to this topic. Note: BBcode and smileys are still usable.
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Re:Converting Mercury Prop to Johnson Outboard Motor 13 years 4 days ago #72684

skipthescrounger Offline Contributing Member Posts: 903 Karma: 33 Thank you received: 0	Buy bigger meaner Merc to go faster. Check this box to be notified of replies to this topic. Note: BBcode and smileys are still usable.
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Re:Converting Mercury Prop to Johnson Outboard Motor 13 years 3 days ago #72691

Chinewalker Offline Gold Boarder Posts: 548 Karma: 42 Thank you received: 10	What RPM are you running with the Raker? The crossflow V4s are happiest when running in the upper 5000s, maybe even touching 6000 RPM with a light load. Check this box to be notified of replies to this topic. Note: BBcode and smileys are still usable.
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Re:Converting Mercury Prop to Johnson Outboard Motor 13 years 2 days ago #72714

dpanky Topic Author Offline Junior Boarder Posts: 109 Karma: 11 Thank you received: 0	With the 22" Raker with one on board, I hit 55.0 MPH GPS at 5,450 RPM. The speedometer is optimistic at 61 MPH. With the 20" Raker and three on board, about 52 to 53 MPH. Do you think it would be safe to try the 20" Raker with one person? Attachments: Check this box to be notified of replies to this topic. Note: BBcode and smileys are still usable.
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Re:Converting Mercury Prop to Johnson Outboard Motor 13 years 2 days ago #72731

Ponyboy Offline Gold Boarder Posts: 605 Karma: 24 Thank you received: 0	I have one already converted to the 13 spline, I think its a 13x22 long ear 2 blade, merc lists it as a (race) prop. its no good for mercs anymore, and I have not used it yet so I cannot tell you if its any good. Check this box to be notified of replies to this topic. Note: BBcode and smileys are still usable.
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Re:Converting Mercury Prop to Johnson Outboard Motor 13 years 1 day ago #72751

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If the 20" prop with one person touches 5900-6000 RPM without going over, then that's where the engine will be happiest. Playing with props that keep the RPM in that ballpark will result in the best performance overall. Might want to play with engine height, too. Some cupped props will hold the water better as you jack the motor up. Keep an eye on your cooling water, too as you don't want to go too high and lose your prime.

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Re:Converting Mercury Prop to Johnson Outboard Motor 13 years 14 hours ago #72766

dpanky Topic Author Offline Junior Boarder Posts: 109 Karma: 11 Thank you received: 0	Thank you for the advice. Will resume testing next spring with hopefully the 21" pitch 2-blade bronze converted to a Johnson spline, a borrowed or purchased 23" pitch SRX, and the 20" pitch Raker. May raise the motor one notch from the present 3/4" off the transom. Check this box to be notified of replies to this topic. Note: BBcode and smileys are still usable.
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Re:Converting Mercury Prop to Johnson Outboard Motor 13 years 34 minutes ago #72781

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The outer diameter of the prop is the same as the outer diameter of the bullit of the OMC lower unit. so it will make the prop completly useless for a merc. Im looking for a pic of mine but not finding it. what is the merc part # of the prop your wanting to use ?

the center prop in this pic is the one I had done to fit the omc gearcase.

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Re:Converting Mercury Prop to Johnson Outboard Motor 12 years 11 months ago #72791

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The 2-blade bronze prop I hope to covert is part number 48-49630-21, pictured above and below. I also have a prop like the three you have pictured, a 22" pitch Hi-performance 2-blade but I do not know how they perform. The 48-49630-21 is a proven to me prop that goes fast.

Is it necessary for the front of the prop metal to fit inside the gear housing? Could one cut back the front of the prop to have it almost butt against the gear housing?

David Pankonin
612-363-3704

What did you do to make the Mercury prop useable for a OMC outboard?

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Re:Converting Mercury Prop to Johnson Outboard Motor 12 years 11 months ago #73131

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I measured the Johnson lower unit gear case outside and inside wall diameters and the Mercury Quicksilver propeller. Both outside walls are 4". Appears that the front flange of the Mercury prop will have to be cut off so that it butts close (1/8"?) to the back of the Johnson lower unit - both 4" in diameter.

The trick will be to cut off just enough of the front prop flange after rehubbing with a Johnson hub and using a Johnson thrush washer.

May rehub both the 21" and 22" bronze props.

The props will be called "Long John Silver"

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Re:Converting Mercury Prop to Johnson Outboard Motor 12 years 11 months ago #73250

Ponyboy Offline Gold Boarder Posts: 605 Karma: 24 Thank you received: 0	It seems a waste but Ive done it too. Ive been looking for a pic of mine but I cant find one, the prop is on the motor backed up to a wall for the winter (first boat in). and yes rehub it first and cut as you need to. mine sets about .025" away from the motor. Check this box to be notified of replies to this topic. Note: BBcode and smileys are still usable.
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Re:Converting Mercury Prop to Johnson Outboard Motor 12 years 11 months ago #73294

dpanky Topic Author Offline Junior Boarder Posts: 109 Karma: 11 Thank you received: 0	Ponyboy, have you had a chance to test the Hi-performance 22" bronze prop on a Johnson? Does the outboard need to be raised on the transom to work? Still debating whether or not this prop will be faster than a Raker 22". Pictures of a Hi-Performance 22" bronze and a Raker 22". Attachments: Check this box to be notified of replies to this topic. Note: BBcode and smileys are still usable.
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Re:Converting Mercury Prop to Johnson Outboard Motor 12 years 11 months ago #73306

Ponyboy Offline Gold Boarder Posts: 605 Karma: 24 Thank you received: 0	I never got the chance to use my converted prop. But I did run across this kalamazoo.craigslist.org/boa/3522022900.html Check this box to be notified of replies to this topic. Note: BBcode and smileys are still usable.
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Re:Converting Mercury Prop to Johnson Outboard Motor 12 years 11 months ago #73316

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Looks like a converted Mercury chopper. It would be interesting to try, but I would like a through-the-hub exhaust and at least a 21" pitch. Some of the people here in the Twin Cities, MN have the SRX 23" pitch over-the-hub exhaust prop for my motor that I may try.

What pitch is your Hi-performance Mercury prop? What are you going to try it on?

Here is a picture of a 22" Mercury Chopper that I sold without trying it on a 115 HP Merc.

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Re:Converting Mercury Prop to Johnson Outboard Motor 12 years 9 months ago #74874

Ponyboy Offline Gold Boarder Posts: 605 Karma: 24 Thank you received: 0	..Not exactly a close up but it is a pic. Its getting warmer every day so I should be getting the ol boat out soon. Attachments: Check this box to be notified of replies to this topic. Note: BBcode and smileys are still usable.
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Re:Converting Mercury Prop to Johnson Outboard Motor 12 years 9 months ago #75043

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Ponyboy, after testing the Mercury prop on the Johnson, post the results. Hope it is your best prop. If you are not satisfied with it, I would be interested in testing it on my 16' Glastron/Carlson
with a 115 HP Johnson. We could work out some arrangement. In the meantime, I have given up on my conversion, thinking that a OMC Raker might be the best prop for me. Here is my e-mail address:
This email address is being protected from spambots. You need JavaScript enabled to view it.

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Re:Converting Mercury Prop to Johnson Outboard Motor 12 years 6 months ago #78411

Ponyboy Offline Gold Boarder Posts: 605 Karma: 24 Thank you received: 0	Well I just sold the boat that I was going to rig with the 115 evinrude. I think I could sell this prop now. any offers befor I ebay it? Check this box to be notified of replies to this topic. Note: BBcode and smileys are still usable.
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Re:Converting Mercury Prop to Johnson Outboard Motor 12 years 6 months ago #78435

dpanky Topic Author Offline Junior Boarder Posts: 109 Karma: 11 Thank you received: 0	Ponyboy, I may be interested in your Mercury prop rehubbed OMC. If you could generally describe it's condition, diameter, pitch, Mercury part number and the price you want from it. Thanks. David Check this box to be notified of replies to this topic. Note: BBcode and smileys are still usable.
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Re:Converting Mercury Prop to Johnson Outboard Motor 12 years 6 months ago #78452

Ponyboy Offline Gold Boarder Posts: 605 Karma: 24 Thank you received: 0	waiting for the battery's to charge in the camera, but I can put up the prt #, 48-55458A4 24p the book shows it for 1970 1150 and 1350 up to 1200# 53-63 mph. Attachments: Check this box to be notified of replies to this topic. Note: BBcode and smileys are still usable.
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Re:Converting Mercury Prop to Johnson Outboard Motor 12 years 6 months ago #78458

dpanky Topic Author Offline Junior Boarder Posts: 109 Karma: 11 Thank you received: 0	Wish that prop were a 22" pitch. 24" pitch may be too steep for me. Interesting prop. Check this box to be notified of replies to this topic. Note: BBcode and smileys are still usable.
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Re:Converting Mercury Prop to Johnson Outboard Motor 12 years 6 months ago #78461

Ponyboy Offline Gold Boarder Posts: 605 Karma: 24 Thank you received: 0	ths is set up for omc 13 spline, same thrust washer etc. Im into it for just over 200.00, would take a reasonable offer, shipping from 46062. This email address is being protected from spambots. You need JavaScript enabled to view it. Check this box to be notified of replies to this topic. Note: BBcode and smileys are still usable.
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TOPIC: Converting Mercury Prop to Johnson Outboard Motor