1971 Evinrude 50173S reverse slipping

Hello everyone, I've read the previous posts regarding this motor, and I can't find what I'm looking for regarding this issue. Last season I changed the lower unit oil (type C) as usual, before launching my boat. The motor started & shifted into reverse with no problem at idle. However, when I raised the rpm even a little, it slipped out of gear. I nursed it while out for the day, by only using reverse in idle to accomplish whatever manuevers were needed. When I got the boat back home, I drained the LU oil again & refilled with new Type C ... from the bottom drain plug until it flowed from the upper vent plug. The next time I launched I had the same problem in reverse when the rpm was raised slightly. Forward & nuetral work fine, and shifting into reverse works fine. It is only slipping out of reverse. There are no signs of debris or metal in the drained fluid, and no signs of water/oil. Could this be a weak solinoid, or a damaged reverse gear, or.....? I'm set on keeping this motor, regardless of "some" of the negative feedback. However, I hope that doesn't turn off anyone's suggestions & help. Thanks in advance

Re: 1971 Evinrude 50173S reverse slipping

I'm hoping to get some help on this issue from you guys. I posted this problem last year as well, but haven't recieved any responses! Am I wording things wrong?

Re: 1971 Evinrude 50173S reverse slipping

Sounds like a bad clutch dog and reverse gear or an oil pump screen in the lower unit that is clogged up.

Re: 1971 Evinrude 50173S reverse slipping

Thanks. Looks like I'm going to tear it down and investigate. I just bought a service manual. I intend to rework the powerhead as well.

Re: 1971 Evinrude 50173S reverse slipping

Thanks boobie. You were right on the clutch dog & reverse gear. The oil pump screen looks dirty, but I just replaced it for safe measure. I'm not sure what caused the wear on the clutch dog & reverse gear. In the process, I replaced the clutch spring, dog, & reverse gear. I also did an ohm test on the solenoids. The manual said they should be between 5-6 ohms. It takes both solenoids to activate reverse. The upper solenoid was 5.2 ohms, the lower was 4.8 ohms. I suspect a weak lower solenoid caused insufficient extension of the plunger to the pump. I replaced the solenoid. I resealed the lower unit, while replacing the upper driveshaft bearing, and the prop shaft bearings. A new water pump impeller was done as well. Tank test in water was good. Launched for the moment of truth....and all is well under load. It was a successful learning experience. Just thought I would pass the info on to those interested.

Re: 1971 Evinrude 50173S reverse slipping

Back to square one! I put the boat back in the water to go fishing, first time since lower unit repair/rebuild. I started having the same problems with reverse. It will go into reverse at low idle, but not with slightly higher RPMs. While in reverse, it will pop out of gear when RPMs are increased. I pulled the boat out of the water, checked fluid for evidence of water - none, level - full. I know that I followed the service manual recommendations for adjusting the solenoids & plunger heights, "not more than 1/64" below top surface of solenoid". Are there any adjustments I can make to improve the engagement of reverse?

Re: 1971 Evinrude 50173S reverse slipping

I thought I had it all figured out when I rebuilt the lower unit, and took it for a test ride. All seemed to be corrected and working properly. However, I put it back in the water on Sat, for a fishing trip, and it started having the same problems again. I can only shift into Rev gear @ very very low RPMs, and if I increase speed while in rev gear...it will jump out of gear. I don't want to keep trying to "baby" it while in use, because I'm sure it will eventually wear our the reverse gear again. Is there any adjustments that you know of that will help engage the reverse gear? I replaced the screen on the oil pump, the reverse gear, clutch dog & spring. Could the oil pump be dirty or worn out? Is there a cleansing solution that I could run temporarily (@ idle)through the lower unit in place of the Type C fluid? Is there an adjustment I can make to the solenoids & plungers. I set the plungers to the recommended service manual tolerance..."not more than 1/64" below the surface of the solenoid". Would an increase or decrease in that height make an improvement? I'm getting stumped and frustrated!