vovlo sx conversion to duo prop

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mattbags

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My motor is the 4.3 with a sx-c1 drive with 1.79 gear ratio. I want to change to a duo prop. Do I need to change to a higher gear like the 2.30 that came factory with the dup prop boats or just leave the 1.79 gears in it and get different props? I did search but found nothing specific. from what I have found with the sx-c1 lower unit I can just find a dp-s lower unit and swap them. IS this corrct in my findings?
 
slasmith1

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Re: vovlo sx conversion to duo prop

Just the lower is different. The question would be is the boat you are doing this to worth the cost. Just the props are going to run you about $1300 if you can find a set used.
 
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mattbags

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Re: vovlo sx conversion to duo prop

I'm trying to find the quote from dons about "worth to you". For what I have into it I'm still on the good side.
 
Don S

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Re: vovlo sx conversion to duo prop

Do I need to change to a higher gear like the 2.30 that came factory with the dup prop boats or just leave the 1.79 gears in it and get different props?
Click to expand...

You will need the complete 2.30 lower unit and a set of props. Understand, the lower units for a duoprop drive has two counter rotating shafts, unlike the single prop drives with only 1 shaft. You can't just put a set of duoprops on a single prop drive.
 
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mattbags

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Re: vovlo sx conversion to duo prop

what do you mean complete lower unit? I have changed plans. I found a 1.60 complete drive. So I am going to take the lower off of that drive and put it on my 1.79 upper drive. Should be a simple swap correct?
 
Don S

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Re: vovlo sx conversion to duo prop

Can you find the Volvo SN for the outdrive or any other numbers on the outdrive?
 
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mattbags

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Re: vovlo sx conversion to duo prop

The numbers on mine are.

Prod# 3858720
Ser# T0821389
 
Don S

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Re: vovlo sx conversion to duo prop

Now I'm finding info on it. It should be an SX-C2, not a C1, The spec number is probably 3868720 not a 385 Volvo nor OMC used a 385 number. You also have the OMC version, not Volvo. The T08 serial number told me that.
Anyway, the 1.79 was used on the 4.3, the 1.60 drive was used on the 5.0L V8, and is the wrong gear ratio for a 4.3L engine.
 
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mattbags

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Re: vovlo sx conversion to duo prop

yeah it was hard to tell if its a 5 or 6. Thank you don. So does that mean I'm SOL on just using the lower from the 1.60 drive? On the motor tag it says
TSK SX-c1 (gas). Also original owner said motor was replaced about 3 years ago.
 
Don S

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Re: vovlo sx conversion to duo prop

What year is your boat? And no, you can't use the 1.60 lower, that's where the gear ratio changes, not in the upper.
 
Don S

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Re: vovlo sx conversion to duo prop

That drive number (3868720) is for a 98.
 
Don S

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Re: vovlo sx conversion to duo prop

I was just looking at the OMC specs for 96, and there were no 1.79 gear ratio drives then. They were using a 1.66. So you may get away with using a 1.60, but you will probably have to reprop.
 
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mattbags

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Re: vovlo sx conversion to duo prop

Even better haha. I might as well give you the number on the engine.
4112016220 4.3gl pnca are the numbers I can make out.

I think these numbers are the transom shield numbers 4111534965 and 3868404
 
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mattbags

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Re: vovlo sx conversion to duo prop

I was looking thru the seloc book the wife got me and the 1.79 didnt show up til '98. (the oem manuals have not arrived yet)
 
Don S

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Re: vovlo sx conversion to duo prop

4112016220 & 4111534965
Click to expand...

Those, are Volvo serial numbers. The engine is a 96 (NC is the model designation). If you look up in the Adults only sticky in the Volvo secetion you will find manuals for the engine and drive.
 
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mattbags

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Re: vovlo sx conversion to duo prop

Well with the drive being a 98. What drive manual would I look at? Still the NC SX or with it being a 98 would it be a sx-m?
 
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mattbags

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Re: vovlo sx conversion to duo prop

Thank you very much Don. I think I found another complete drive. It is a 1.66 which came on those boats in my year range. I'm still trying to find the duoprop setup in my price range though.
 
Don S

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Re: vovlo sx conversion to duo prop

Sure hope you find one. If you do, you can expect to feel like you put a bigger engine in your boat. Much better hole shot, lower rpm at same speed, low speed control both forward and reverse are WAY better. You won't believe it's the same boat.
 
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