OMC sterndrive not moving in gear.

[racerone]

Yours appears to be a 400 model I can only guess that from 1000 miles away.

 

[Redrig]

what engine is in your boat ?

 

[Serf27]

what engine is in your boat ?

A 3.8l v6.
The seller was insistent that it would fit my boat.

 

[Scott Danforth]

A 3.8l v6.
The seller was insistent that it would fit my boat.

You have a stringer 800. However the V6 has different gearing than the V8

 

[Serf27]

You have a stringer 800. However the V6 has different gearing than the V8

Thank you for confirming.
So how would the boat behave with that drive?
Better, worse or about the same?

 

[Scott Danforth]

Thank you for confirming.
So how would the boat behave with that drive?
Better, worse or about the same?

With the wrong gearing, you have to drop down in pitch on the prop. If your current prop is a 21 pitch, you can drop to a 15 or 17. However there are not props below 15.

I would get the right gear ratio

 

[Redrig]

Yeah , like Scott said , get the right ratio. I had to search and search for the right drive on mine when I did my conversion.

Your upper unit will have a certain ratio , the lower unit will have a certain ratio. Combined together gives you the overall ratio.

Try to get that overall ratio exact , or as close as possible. Otherwise you will have to change out your props to be able to hit wot.

 

[Redrig]

 

[Redrig]

Full disclose- these numbers are from an OEM 1985 manual. Idk if they are perfect for your model, but I would have to imagine they are close.

 

[Serf27]

Well darn. I ordered the drive early this morning before I was aware of this.
The seller was insistent it would fit, despite some minor physical differences I brought up.
I will just return it if it doesn’t work out.

I was not expecting a new $100-$150 propeller, as I asked the seller too if my propeller would work and was told yes.

Haven't a clue what my current pitch is, I need to check the propeller tomorrow.
I do know it accelerated somewhat quickly the other day when in the water…

 

[Serf27]

Would this 15.5x15 work?

Michigan Wheel 011006 Michigan Match 15.5x15 OMC 800 SX Cobra sterndrive | eBay

Find many great new & used options and get the best deals for Michigan Wheel 011006 Michigan Match 15.5x15 OMC 800 SX Cobra sterndrive at the best online prices at eBay! Free shipping for many products!

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Or

For Johnson/Evinrude/OMC OEM Propeller 13.25x17 Prop 765183, 0765183 741754326557 | eBay

Find many great new & used options and get the best deals for For Johnson/Evinrude/OMC OEM Propeller 13.25x17 Prop 765183, 0765183 at the best online prices at eBay! Free shipping for many products!

www.ebay.com

 

[Scott Danforth]

Well darn. I ordered the drive early this morning before I was aware of this.
The seller was insistent it would fit, despite some minor physical differences I brought up.
I will just return it if it doesn’t work out.

I was not expecting a new $100-$150 propeller, as I asked the seller too if my propeller would work and was told yes.

Haven't a clue what my current pitch is, I need to check the propeller tomorrow.
I do know it accelerated somewhat quickly the other day when in the water…

fit - yes
work correctly - no

 

[Scott Danforth]

Would this 15.5x15 work?

Michigan Wheel 011006 Michigan Match 15.5x15 OMC 800 SX Cobra sterndrive | eBay

Find many great new & used options and get the best deals for Michigan Wheel 011006 Michigan Match 15.5x15 OMC 800 SX Cobra sterndrive at the best online prices at eBay! Free shipping for many products!

www.ebay.com

Or

For Johnson/Evinrude/OMC OEM Propeller 13.25x17 Prop 765183, 0765183 741754326557 | eBay

Find many great new & used options and get the best deals for For Johnson/Evinrude/OMC OEM Propeller 13.25x17 Prop 765183, 0765183 at the best online prices at eBay! Free shipping for many products!

www.ebay.com

you wont know until you now put it together and find out how far you have to drop in pitch

about 200 RPM for every 1" of pitch.

what prop do you have now?

 

[racerone]

What spline is on your prop shaft ?-----Is it 13 or 15 teeth ??

 

[Redrig]

The pics I posted above show that in the 85 models the 3.8 , 5.0 and 5.7 all have the same lower unit (14:26) . It looks like the ratio change was done in the upper for the different engines. Or am I missing something ?

Does anyone know if that is indeed the case for all years of omc 800s?

Cuz op , you might be just fine with that lower unit .

 

[Serf27]

Thanks all.
I just looked at my prop.
The markings on it say 13 3/4 X 15.
So it is a 15 pitch propeller?
My prop shaft has 13 splines.
My 1984 manual looks the same as the 1985 book Redrig posted.
I did also notice that the lower drive ratio for all. 3.8l, 5.0l, 5.7 is 14:26.

Here are some photos.

 

[racerone]

Count the splines again.-----Count the splines again.----I am convinced you have a 400 model lower unit.----13 splines and a coarse thread on the prop shaft !!!!!----Post #21

 

[Serf27]

Here is my prop shaft.
I will re count the splines again.
I corrected a mistake I made earlier, I counted 13 splines, not 14, but will double check.
First 2 are mine, second one is the one on the eBay unit.

 

[Redrig]

Yeah @racerone nailed it.

I wonder of your upper unit is from a 400 as well. I would confirm exactly what you are working with before proceeding.

Someone has swapped things out and didn't match it up properly.

(Did they swap the whole drive or just the lower unit ????)

 

[Serf27]

Well this is news to me!
I have been using the manual and parts diagram based off of the serial number on the engine.
All parts I’ve installed have fit.
The serial number is 382SPMRCRJ and brings up this when I search the online parts catalog.
“1984 OMC 382SPMRCRJ 3.8L Stern Drive”
The last digit, I believe the J is missing from my serial number but it’s the closest one I found.

So what now?
I see a used 400 lower drive forsale, but it says for 4cylinder engines. Mine is a V6.
Here is a photo of my upper drive….