Problems with my 1973 Johnson 25hp

[outlawfox13]

Ok, well I picked up this motor for $250, and the PO hadnt run it so had no idea how it ran. I did a compression test and got 135 on top and 133 on bottom so I was pleased and bought it. I replace the impeller and rebuilt the carbs, new plugs and gapped to .030 also replaced thermostat and changed lower unit fluid. I was gonna pull the flywheel, but the ignition coils and wires looked new so I havent pulled it yet, got it running great in a bucket, then took it out today for its initial run. It idled great, and started to pick up power well, then all of a sudden the motor jolted before I got up on plane and knocked the motor out of gear. so I put it back in gear and held it down as I throttled up, then it jolted again and I could feel the motor pick up just a hair then slow down a lil and maintain, then about ten seconds go by and it does the same. so for the whole test ride it does this about every ten seconds or so. I am thinking that the points may be off so I will check later, does any one know what this could be? It is a pretty heavy jolt like I hit somthing, oh and what needs to be adjusted or repaced to keep the gear selector down, Im thinking somthing is worn down for it to pop out of gear when the motor jolted.

Thanks in advance Mike

 

[kfa4303]

Re: Problems with my 1973 Johnson 25hp

Hi outlawfox13. Welcome to iboats. Glad you got your motor running again. The sudden jolt you described sounds like you may have a worn clutch dog and/or you may need to readjust the shift rod linkage. I would start with re-adjusting the shift rod, then running the boat again. If that doesn't do it then you'll probably need to look at the clutch dog. It only takes a little bit of wear for them to start to fail. Here's a link to a parts catalog with exploded diagrams of your motor just click on your particular model.


http://www.marineengine.com/parts/johnson-evinrude-parts.php?year=1973&hp=25

 

[outlawfox13]

Re: Problems with my 1973 Johnson 25hp

Thanks for the tip and the welcome, I am quite familiar with this site as I used aot of info and the top secret folders to get my 68 18hp evinrude running. I went to the site and put in my model # now what is a clutch dog? I have heard of them before but dont know what it is. Thanks

 

[F_R]

Re: Problems with my 1973 Johnson 25hp

The clutch dog is the part that slides back and forth on the propeller shaft, engaging either the forward or reverse gears. Yours is worn out, which is what is kicking it out of gear. It is also what is making it bang like you hit something.

 

[Larry Glady]

Re: Problems with my 1973 Johnson 25hp

could it be a lean sneeze carb ajustment???

 

[F_R]

Re: Problems with my 1973 Johnson 25hp

That might be, if it were at idle speed. He is describing a bang like he hit something at high speed and kicking it out of gear. Clutch dog for certain. Probably the forward gear too. And if it has continued long enough, it may have destroyed the shifter lever inside, under the powerhead. Sounds like it has been going on for a long time. It didn't get that way overnight.

 

[outlawfox13]

Re: Problems with my 1973 Johnson 25hp

Well, that sucks, i was worried it would be a problem with the gear case. Is it a hard fix? I have done points n coils as well as rebuild a set of carbs but never really messed with the LU. Also what year LU's will fit my motor. I am asking because i have a 68 evinrude 18hp that i am switching out for the 25 any ways.

 

[kfa4303]

Re: Problems with my 1973 Johnson 25hp

Hello again outlaw. Here'sa pic that shows you how/where the clutch dog is. Thankfully, it's a very easy fix. You just slide the old one off and slide the new one on. You will have to open the gear case, but it's not as bad as you may think and you'll learn lots about your motor in the process. You may as well reseal the LU while your at it. It's a quick cheap (about $25 available right here at iboats) job that will keep the LU watertight for years to come. There are lots of threads here the forums that can walk your through the job, or just holler if you get stuck.

How to reseal a Lower unit: http://forums.iboats.com/showthread.php?t=277190&highlight=lower+unit+seal+kit+installation


Gear case cut away:

Great overall tune up link(s): http://www.duckworksmagazine.com/07/columns/max/index1.htm
http://www.outboard-boat-motor-repa...on 3 HP 1952-1967 Ignition System Tune-up.htm

Exploded Parts diagram for your motor. Just click on your particular model: http://www.marineengine.com/parts/johnson-evinrude-parts.php?year=1973&hp=25

 

[F_R]

Re: Problems with my 1973 Johnson 25hp

Or, the 18hp will fit, if you want to go that way.

 

[kfa4303]

Re: Problems with my 1973 Johnson 25hp

you may want to look for a donor motor/LU, you may actually be able to get one cheaper than buying a brand new clutch dog.

 

[outlawfox13]

Re: Problems with my 1973 Johnson 25hp

Thats my plan, but for now I am just gonna use my LU from my 18hp till I get a donor or a new clutch dog. Thanks for all the help!!!

 

[outlawfox13]

Re: Problems with my 1973 Johnson 25hp

Ok I swapped the LU's as a quick fix and all is good on that term, but I still want to repair the other LU. I found a set of gears from a 66 Johnson 20hp, but all the part #'s are different. I know as a whole unit they are interchangeable(as it is working now) but are the internal gears interchangeable(if I use all from same motor)? Thanks Please let me know asap as I have found a good deal on a set of used gears. Thanks Mike