Logo
FULL SITE MENU

OK remind me...will a Duoprop SX lower fit on a Cobra upper?

OK well, what you're telling me is yes. Not real swift with the nomenclature as yet. What's in the kit?
Never mind. Found it.
 
Last edited:
Apparently some are using the OEM Cobra seawater path from the drive to the now engine located seawater pump.

My thoughts area..... this path was previously under pressure from the OMC drive located seawater pump.
The new engine mounted seawater pump will now be pulling (suction) from/through this path.
Since suction requires a larger and less restrictive path...... this may mean a thru-hull seawater pick-up would be best!

Your call on that!



.
 
Oh yeh def on the seacock. I don't trust the sh(not very well engineered)tty Cobra pump as it is and trying to get adequate cooling water all the way up thru the drive, well....
My only question mark at the moment is the shift mechanism. The Cobra shift rod is toward the front. How would the Volvo link up? The Volvo upper has this Rube Goldberg bell crank pushing a bell crank craziness.
 
It appears that the forward-reverse shifting occurs in the upper unit of the drive on the Volvo, so I guess you cant just slap a Duoprop on a Cobra
 
o2batsea said:
It appears that the forward-reverse shifting occurs in the upper unit of the drive on the Volvo, so I guess you cant just slap a Duoprop on a Cobra
Click to expand...

That is correct!
Gear engagement occurs in the upper unit on a Volvo Penta.
If you do an OMC Cobra to Volvo Penta SX or DP-S conversion, you will be changing parts from the "Gimbal Bell" or "Pivot Housing" back!





.
 
1) to do the conversion yes you need to replace the Cobra pivot housing with the Volvo SX pivot which is slightly longer. The water tube set up is exactly the same. Shift cable comes thru the same way as the Cobra.
2) adding the engine mounted pump is not a problem because this is exactly the same way the Volvo SX cooling system is set up. Keep in mind that the 94-98 OMCs and 94&up Volvo SXs were the joint venture OMC/Volvos and were set up the same exact way.
3) If installed properly there is absolutely nothing wrong with the Cobra impeller in fact they are about the easiest one to replace that there is. Can even be done in the water in a pinch!

I researched the Cobra to SX conversion extensively but my Cobra has held up so well even in salt water that the conversion is not necessary as long as I can get the Cobra parts I need....
 
With Cobra drives available for roughly one tenth of what a basket case Duoprop drive sells for, I can get a LOT more out of mine. It's actually a lot cheaper to put in a bow thruster than convert to Duoprop. I'm mostly concerned with low speed manoevering since the ramp is super tight and in a breeze can be tricky. Fortunately there is usually nobody at the ramp but me so my failures are not subject to public ridicule...much.
 
.............................

louc said:
1) to do the conversion yes you need to replace the Cobra pivot housing with the Volvo SX pivot which is slightly longer. The water tube set up is exactly the same. Shift cable comes thru the same way as the Cobra.
2) adding the engine mounted pump is not a problem because this is exactly the same way the Volvo SX cooling system is set up. Keep in mind that the 94-98 OMCs and 94&up Volvo SXs were the joint venture OMC/Volvos and were set up the same exact way.

While some may call this era a "joint venture" era, I can assure you that the drive was completely re-designed for the 1994 and later production.
The OMC Cobra is a Dog Clutch drive........ the Volvo Penta SX or DP-S are cone clutch drives.
Click to expand...

o2batsea said:
It's actually a lot cheaper to put in a bow thruster than convert to Duoprop.
Generally speaking...... people are purchasing a Duo Prop drive for much more than the docking improvement alone.
Click to expand...
 
Generally speaking...... people are purchasing a Duo Prop drive for much more than the docking improvement alone.
Click to expand...

Yeh but they probably have NICE boats and not a hooptie like mine...
 
RicardoMarine said:
.............................
Click to expand...
yes it was completely re designed, I'm not sure who did most of the engineering but the only part changed on the transom mount was the pivot housing; the rest was the same as OMCs design.
BTW OMC had already designed their own cone clutch drive; the Daddy King as it was known in 1990 4 years before the joint venture...
 
......................
louc said:
yes it was completely re designed, I'm not sure who did most of the engineering
OMC's numerous failures lead to their filing for chapter 11.
That said......, I would suggest that the Volvo Penta Engineers were much more involved when the SX/DP-S Gimbal System drive was being designed.

but the only part changed on the transom mount was the pivot housing; the rest was the same as OMCs design.
NOT so!

The standard OMC Cobra was a Dog Clutch drive.
I.E., 2 gears only in the upper drive unit...... and w/ 3 gears and a sliding (dog clutch) sleeve in the lower drive unit.

Volvo Penta has always used Cone Clutch gear engagement.
I.E., 3 gears and a conical sliding sleeve in the upper transmission unit..... and with only 2 gears (s/p drive) in the lower drive unit.
(the duo prop lower unit has 3 gears)

BTW OMC had already designed their own cone clutch drive; the Daddy King as it was known in 1990 4 years before the joint venture...
OMC eventually gained the rights to use Volvo Penta's pattented cone clutch design for their KC CC drive.
Click to expand...
 
Rick I was only referring to the transom mount not the whole drive. Yes the drive was completely re designed but not so for the transom mount. Look at pix of the two designs...
 
Back
Top