1973 Evinrude 25HP, Breaking Shear Pins??

[johndreid]

I have a 73 25hp evinrude that runs great....untill you get up past an idle. At that point the engine jerks/misses hard about every 3-5 seconds. It jerks pretty hard. After jerking/missing or whatever it's doing a few times the shear pin for the prop breaks. I'm assuming its because the prop is slowing down and trying to catch up to speed too fast......???

I've changed a coil pack that was cracked and installed all new points and condensers with no change in the miss.

My brother used the NEW gas tank out of the boat and said that his boat, which runs perfect, started doing about the same thing. He did however forget to open the vent on the tank........so again....Not sure. I may have to try another tank...I'm just not convinced of that being the problem yet.

Someone else mentioned the gears in the lower end. The forward and reverse gear looks fine although I haven't completely removed them from the unit. There was alot of finely ground metal flakes in the oil...about like the size of black pepper.......

Any ideas as to what could be going on?

Thanks in advance,
John

 

[F_R]

Re: 1973 Evinrude 25HP, Breaking Shear Pins??

I have a 73 25hp evinrude that runs great....untill you get up past an idle. At that point the engine jerks/misses hard about every 3-5 seconds. It jerks pretty hard. After jerking/missing or whatever it's doing a few times the shear pin for the prop breaks. I'm assuming its because the prop is slowing down and trying to catch up to speed too fast......???

I've changed a coil pack that was cracked and installed all new points and condensers with no change in the miss.

My brother used the NEW gas tank out of the boat and said that his boat, which runs perfect, started doing about the same thing. He did however forget to open the vent on the tank........so again....Not sure. I may have to try another tank...I'm just not convinced of that being the problem yet.

Someone else mentioned the gears in the lower end. The forward and reverse gear looks fine although I haven't completely removed them from the unit. There was alot of finely ground metal flakes in the oil...about like the size of black pepper.......

Any ideas as to what could be going on?

Thanks in advance,
John

No doubt about it, the clutch dog and forward gear are totally worn out. Possibly the shift linkage too, because one damages the other. What you are experiencing is it jumps out of gear, rotates 1/2 turn and slams back into gear. Then it does it again, and again....

It will happen long before it gets anywhere near as bad as the one in this picture.

 

[johndreid]

Re: 1973 Evinrude 25HP, Breaking Shear Pins??

One of the ears on the clutch dog that engages forward gear is slightly rounded on one corner...but...........I found another problem....

You know how the engine pretty much throttles up and down with the timing at low speeds?....I don't know what you call it but, the peice under the flywheel that turns clockwise against the throttle lever to push open the throttle untill you get up to speed......well it wasnt adjusted correctly and the throttle on the carb. was not being used untill the timing advanced all the way as far as it would go. I'm assuming that this means I was not getting the correct ammount of fuel into the engine to match the timing...........

Could that explain my miss?

I don't want to pull the gears just yet if that could have been the problem.

Thanks,
John