RZ21 OB

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BradSpencer

Well-Known Member
Joined
May 7, 2009
Messages
890
It's been while since I have tinkered with a boat engine, thought I would share my current project.

Being a big fan of OS engines and outboards and with the help from KRE I converted this RZ On road car engine to an outboard.

Looks similar to a 21xm OB, but it is quite different internally. These were a great car engine, and the marine version (RZM) had good reviews back in the day.

Using a 21xm crank, case bored to fit the 21xm PTO.

20G carb, the standard extended barrel machined shorter to take 21xm throttle arm.

Minor mod to flywheel to clear case.

Hope to give it a run in the new year:).

IMG_7266.JPGIMG_7268.JPGIMG_7267.JPG
 
I have an OS based engine I got from Rody over in France to test after the ice is off the lakes. It came with a huge air cooled head that dont usually work well in the cooler climate I live in. Just for kicks I grabbed an Orlic Novarossi head I had in my part stash and it bolts right on.testing will begin in May.2826C96C-4117-4EE8-A0DA-954A09935835.jpegF41D572D-0B77-4CC4-8D30-90278F4DB588.jpeg
 
Very nice looking mil there Larry. With OS quality and Rody's knowledge no doubt this is a great powerhead option. Very reasonably priced as well....

I have been looking to get a couple of these for a while now, just haven't had the spare funds to pull the trigger.

Looking forward to hearing your thoughts.
 
I have an OS based engine I got from Rody over in France to test after the ice is off the lakes. It came with a huge air cooled head that dont usually work well in the cooler climate I live in. Just for kicks I grabbed an Orlic Novarossi head I had in my part stash and it bolts right on.testing will begin in May.
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Larry. What engine is that? Was any machine work required to make the outb version?
Sent from my SM-N920V using Tapatalk
 
Alan,

The link Brad posted will take you to Rody’s website. Their is now a water cooled version of this engine available as shown in the link. Mine came with a buggy size air cooled head that I swapped out for a water jacket made for a Novarossi that just happens to fit. Carb is a OS 21D off an inboard engine that OS used to produce. The engine has been heat cycled through a few tanks of fuel but I have not had it in the water yet. -2F right now at my house and last week when I was out on the lake fishing there was about 11” of ice. Performance analysis will have to wait...

Till about May.
 
I have an OS based engine I got from Rody over in France to test after the ice is off the lakes. It came with a huge air cooled head that dont usually work well in the cooler climate I live in. Just for kicks I grabbed an Orlic Novarossi head I had in my part stash and it bolts right on.testing will begin in May.
attachicon.gif
2826C96C-4117-4EE8-A0DA-954A09935835.jpeg
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F41D572D-0B77-4CC4-8D30-90278F4DB588.jpeg
That`s a great engine, you won`t be disapointed. However you may need to modify your headbutton to allow some tighter squish. I was not able to get any tighter squish than 0,80 mm, makes it very lazy ;-)
 
I have an OS based engine I got from Rody over in France to test after the ice is off the lakes. It came with a huge air cooled head that dont usually work well in the cooler climate I live in. Just for kicks I grabbed an Orlic Novarossi head I had in my part stash and it bolts right on.testing will begin in May.
attachicon.gif
2826C96C-4117-4EE8-A0DA-954A09935835.jpeg
attachicon.gif
F41D572D-0B77-4CC4-8D30-90278F4DB588.jpeg
That`s a great engine, you won`t be disapointed. However you may need to modify your headbutton to allow some tighter squish. I was not able to get any tighter squish than 0,80 mm, makes it very lazy ;-)
Mine is set at .006” A fellow TCMBC member raced one of our September races with the water cooled version on a Vision and it was running very strong. If memory serves me right he was running a Silver Bullet pipe and a CMB carb. I don’t know what he had for squish clearance.
 
Brad, how are you doing on your newbuilt engine?

Im about to check out several OS engines my self, just for fun and maybe be lucky enough to find a good match.

The old 21 RX is almost the same as 21 XM.

The RX offroad engine and XM outboard use the same P/L.

I just ordered a P/L for the RX-R on-road engine just to check out how it works, it will fit the 21 XM engine as well as the RX.

About the RX-M I dont know if it has the same timing as RX-R, but probably not since they dont share the parts number.

Will soon check out a VZ-M as well, if I can do an easy outboard convertion.
 
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Hey Joern,

I haven't had a chance to run a boat in a while now, I am very keen to test the RZ OB though.

That RX outboard project sounds very exciting. Those RX parts are getting rare, glad to hear you could get onto a P/L.

A 14mm OB crankshaft for the VZM with the correct stroke will be the stickler. I have fitted a VZB/VZM p/l to a 21xm case. Took a lot of machine work to get it done.
 
Larry

Can I get more info on the Novarossi water jacket you used. I'd like to buy one for my Rody OS

Perhaps a part number or?

any other ideas for a carb other than the OS 21D carb
 
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