Prop shearing on 1975 25hp Evinrude

[poolshark38759]

my prop pin shears when i run at WOT after a few minutes of running...motor sounds like its running too fast (dont have a tach but would like one..dont know what size prop is on it but seems like needs to be bigger or have more bite....i have it on a 14' PolarCraft (looks like a BassTracker PanFish 16 except live well on the side)...any suggestions??? speed it not important to me..

 

[rickdb1boat]

Re: Prop shearing on 1975 25hp Evinrude

Poolshark<br />From what I can figure using the charts, you should be running a 9 1/4" X 11" Prop. That would be considering a medium load in the boat. The range for Props is in the 9" X 10"-9 1/4" X 12".

 

[steelespike]

Re: Prop shearing on 1975 25hp Evinrude

Not sure what you mean by shearing.<br />You could have a problem with a spun hub.<br /> The rubber hub in the prop meant to protect the drive if you hit something.<br />Take prop off and mark the hub and prop with a line(paint or indeleble<br />marker)drive the boat and see if line changes.<br />A prop shop can replace hub.<br /> It could also be cavitation, cavitation plate<br /> (just above prop)Should be approximately even with the bottom of the boat.If too high prop<br />could be cavitating.

 

[G DANE]

Re: Prop shearing on 1975 25hp Evinrude

Hi poolshark<br /><br />Sheering often occurs when propeller nut is turqued too much. Nut only have to be a little turqued and secured with split pin

 

[poolshark38759]

Re: Prop shearing on 1975 25hp Evinrude

thanx everyone...<br /><br />the pin shears only at sustained WOT...you can back off the throttle to say 3/4 throttle and it wont do it...

 

[G DANE]

Re: Prop shearing on 1975 25hp Evinrude

Oh yes, but overturquing probably is the reason anyway, they only needs to be turques a bit, almost fingertight. Too tight and it will break within minutes. I always ran WOT with my 25 HP - always - my brother in law always run WOT with it now, done for 6 yrs now and its an old 73. Iddles smooth with not a sound almost, even with hood off - wonderfull motors. Been there- done that.

 

[poolshark38759]

Re: Prop shearing on 1975 25hp Evinrude

thanx <br /><br />i will loosen the nut and see how that does..<br /><br />i love these old rudes and johns...<br /><br />however i do have one of each for sale..<br /><br />78 Evinrude 25hp...no cowl or foot, and not running...<br /><br />75 Johnson 25hp on 14' Polarcraft..running but need fuel line from pump to carb and good tune-up and TLC..