shear pin breaking-25 hp

cowfish17

Recruit
Joined
Mar 26, 2006
Messages
2
I have a 1977 25 hp evinrude and the shear pin breaks frequently when I go from an idle into gear. Someone suggested to me that my idle should be adjusted. Any ideas?
 

OBJ

Supreme Mariner
Joined
Dec 27, 2002
Messages
10,161
Re: shear pin breaking-25 hp

Just how fast is it idling cowfish? Welcome aboard!<br /><br />You should be idling down around 650 to 750 rpms. Does it "clunk" when you shift into gear? If so, the idle is high and can cause undue stress on the shear pin causing it to break often.<br /><br />Can you get a timing light with tach capabilities to take a look or maybe a tiny tach?
 

ezeke

Supreme Mariner
Joined
Sep 19, 2003
Messages
12,532
Re: shear pin breaking-25 hp

The shear pin is just taking as much of the shock as it can, which it is designed to do to keep the gears from being ripped apart. When you shift that motor you have to reduce the speed completely back to shift (idle), then from neutral, shift firmly into gear.
 

DHPMARINE

Captain
Joined
Dec 16, 2003
Messages
3,688
Re: shear pin breaking-25 hp

Also be sure you are using the right pins.OMC used different metals for different motors.<br /><br />DHP
 

rodbolt

Supreme Mariner
Joined
Sep 1, 2003
Messages
20,066
Re: shear pin breaking-25 hp

and if the engine is idling correctly check the pin hole in the propshaft for wear and the drive slot in the prop hub for excessive wear, both can shear pins when placed in gear if to sloppy.
 

G DANE

Commander
Joined
Nov 24, 2001
Messages
2,476
Re: shear pin breaking-25 hp

I had that problem untill I discovered that I was overtightening propnut. That nut should only be just tight, and turned to cutterpin holes are aligned, and locked with a cutterpin. If you overtighten you will notice the broken pins looks a bit bent ( though in pieces ) when you take them out. Take it easy.
 

cowfish17

Recruit
Joined
Mar 26, 2006
Messages
2
Re: shear pin breaking-25 hp

thanks guys, you have been very helpful. This is a great discussion board that you have going here
 
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