Have prop, need help

C

charles.manifold

Cadet
Joined
May 16, 2013
Messages
25
Hi all,

I recently acquired my first boat. It has an OMC 3.0 cobra i/o with a tri-blade prop that's all beat to hell... I found one at a garage sale down the road that I picked up for 2 bucks. It looks like its the same as the one I have on there now, but I cant be certain because its so chewed up... So my question is how (if at all) can I determine if this new prop will work on my boat?

Sorry if this is a stupid question, I'm new to boating.

Thanks in advance for any help!
 
jestor68

jestor68

Commander
Joined
Jun 12, 2012
Messages
2,308
Re: Have prop, need help

Depending on what year your boat/stern drive is, it would have the earlier 13 tooth spline shaft or the later 15 tooth spline shaft. I believe 1990 was the year of the change over to the larger hub(15 spline).

Remove the old prop and locate the size numbers usually stamped on the hub. The "new" prop should have some numbers stamped somewhere on the hub also; something like 14 X 19 for example.

Measure the diameter of the old prop's hub; "new" prop must be the same. Early ones were 4-1/4" diameter; later ones are 4-3/4" diameter.
 
S

steelespike

Supreme Mariner
Joined
Apr 26, 2002
Messages
19,069
Re: Have prop, need help

Did they say it was for a OMC Cobra? If not the odds are against it fitting the OMC.
OMC is the odd man out in the I/O world;I think they stopped production in the 90s.
But stranger things have happened.Hope it works for you.
In a pinch you might be able to have the old prop repaired though I would be inclined to get a new one
just to get a known working prop, possibly with the latest technology, designed to work best on your setup.
 
C

charles.manifold

Cadet
Joined
May 16, 2013
Messages
25
Re: Have prop, need help

It is an OMC, I have to run the serial numbers but I think it's an '86-'87... I didn't get a chance to look at the splines on the current one before I left for work, that will obviously be the first thing to check.
I was more so curious about the pitch... It's hard to tell for sure if the pitch is the same on the "new" one. How is that determined?
 
S

steelespike

Supreme Mariner
Joined
Apr 26, 2002
Messages
19,069
Re: Have prop, need help

Look for numbers under the prop nut or near the base of the blades. Diameter X pitch.
A prop shop can measure it/them for you.
 
You must log in or register to reply here.
Top