OMC Cobra Prop Differences

[knvj]

I have a 1992 OMC 3.0L with a cobra sterndrive. I currently run a 15x17 aluminum propeller, part number 391200. I found a stainless steel prop on e-bay, which according to the parts list, should be the correct upgrade, part number 391290. However, there is a difference in the prop hubs. There is a greater distance between the back face of the prop and the hub on the aluminum prop. When the aluminum prop is mounted the thrust bushing fully seats into the prop, when mounting the stainless prop there is not enough clearance for the bushing to fully seat into the prop, however, the thrust bushing does appear to align to the hub and inserts approximately the depth of the chamfer when torqued to the proper amount. When rotating the prop it feels secure, but I am still concerned about these differences and what will happen when I am at high speed. Any body out there aware of this? Your help is appreciated. Thanks.

 

[chiefalen]

Re: OMC Cobra Prop Differences

You looked it up ?

You say it's the right prop for the setup cause i didn't look it up ?

Different makes of props from different manufactures, sit a little different on the shaft.

Heres a site i use.

http://www.piranha.com/prop_search.php

Good luck !

 

[Boatin Bob]

Re: OMC Cobra Prop Differences

I have that exact same PN on my right hand drive and one time when I had it re-hubbed as it started to slip the prop shop put the rubber hub too far up inside the prop which wouldn't allow the thrust bushing to sit down all the way. This made the whole prop sit farther back on the shaft to the point where after I put the spacer on the nut wouldn't grab any of the threads. I had to take it back and get them to put another hub in correctly.

 

[chiefalen]

Re: OMC Cobra Prop Differences

I thought i read correctly, the nut is securing the prop the washer under the nut doesn't go down as far as the other prop.

I got maybe 6 props for my POS none sit like the next one.

If the nut is secure and the teeth engage, cause the nut is one thread back or forth makes no difference.

You still can get the cotter in correct ?

 

[Boatin Bob]

Re: OMC Cobra Prop Differences

If you put the spacer on and then can start the nut and get it turned enough to put the cotter pin in then you should be good to go! I couldn't even start my nut so back it went for another hub.

 

[knvj]

Re: OMC Cobra Prop Differences

Thank you for your help.

I am actually concerned about the thrust washer in the attachment, item number 64, not seating totally into the prop. Yes, I can screw the nut on fully to insert the cotter pin and the prop does feel secure.

 

[Boatin Bob]

Re: OMC Cobra Prop Differences

As far as I know OMC only had that 1 thrust bushing for those props so the only thing I can think of is the prop might have been re-hubbed like mine and they never checked it with the thrust bushing, I wouldn't worry about.

 

[a70eliminator]

Re: OMC Cobra Prop Differences

I replaced the original aluminum prop on my OMC with a SS. The thrust washer set into a recess on the original aluminum, but on the SS there is no recess for it set into, it slightly effected the depth of the spline engagement (width of the thrust washer) less spline into toothed spacer on the nut end, I was a little concerned but just torqed it all down and installed castle pin, so far so good.

 

[knvj]

Re: OMC Cobra Prop Differences

Thanks for your help! I'm ready for the ice to thaw!