Logo
FULL SITE MENU

evinrude 1972 18 hp model 18202, shearing pins in reverse.

T

thomcheek

New member
Had motor this for the last 15 years. Given great service untill I changed the prop, some 5 years ago. Replaced the prop (9x10) for 9x9 as was listed in the parts diagram as a replacement. Since that time the shear pins (bought thru MarineEngine.com) will shear when I put in reverse, not every time but more often than not. I've tried proper shifting techniques as listed in the manual. I've inspected the new propeller and the machined surfaces that accomodate the shear pin and they are not worn and still have factory produced clean edges. The propeller nut seems tight to the shear pin with no play and the cotter pin fits the hole easily. Any hints would be appreciated.
 
Thanks for responding. I tried to use brass as that was the only thing available to me locally at the time. Of course that didn't work, so I broke down and ordered a quantity of (12) - OEM part no.
0307949 as recommended from Marine engine.com. So far, the last 6 times out has used 6 shear pins. I've checked for play in the gear case, no slop- nor has there been an incidence of jumping out of gear. I checked the forum and haven't found anyone with a similiar problem.

I'm a retired marine maintenance engineer ( large ships) and have experienced many strange things, but this one has me stumped. Hope you have an idea .
Thanx, Thom​
 
If it is shearing those stainless steel drive pins there has to be some problem of harsh shifting. I have no idea what it is though. Is the hole through the prop shaft worn out? Did you put a new prop on it, or an old one that the hub may be locked up in? Have to wonder why it doesn't shear when shifting to forward. Something mighty strange going on here. Prop blades hitting the exhaust outlet snout? Thinking outside the box now.
 
Thanx for the input, and yes my sons have had to be schooled on shifting, the hole in the shaft doesn't look worn, however the manuals give no specs on the size,so a snug fitting cotter pin has been installed. The cone was replaced with the new prop. Thinking that possibly the thrust washers may be the problem, one worn more than the other and causing the shear just in reverse. kimcrwbr1 has suggested a brass/stainless washer between the cone and the prop. I,ll try that first before tearing down the gearcase. If that the case, I hope my manuals will supply the tolerances.
Always happy to to entertain all ideas. Will repost my findings after finishing another "project boat" that's about 90% complete.
Have a great day!!!!!
 
thomcheek said:
Had motor this for the last 15 years. 5 years ago. Replaced the prop. Since that time the shear pins will shear when I put in reverse.
Click to expand...

The answer is in your initial statement/post... as listed above.

You indicate that the shifting prior to installing that new propeller was fine and that no problem existed. If so.........

The problem IS NOT the manner of shifting, nor the rpm of the engine. Something is very wrong with that propeller you installed UNLESS a internal malfunction exists within the gearcase (allows the propshaft to move back in reverse).

You didn't mention the reason for replacing the propeller!
 
The pin groove in the original propeller had worn and was slipping without shearing the pin. Replaced the cone also as it was looking ratty and cracked.
 
is there any vibration when running the motor in gear ?is the pin fitting as deep into the prop as it did in the old one?....unless i am having a brain fart the only difference in forward and reverse is the prop is trying to seat the pin deeper into the groove and trying to back off the pin in reverse..

just reread your last entry...the old prop was not fitting deep enough in the groove either in my opinion..
 
Back
Top