25 hp Evinrude dropping out of forward?

[Beek14]

So I recently got my 78 25 hp up and running and everything seems to be good. Got it running nice so I get it out on the lake to try it out. Runs good at low and mid speed, but once it gets going pretty fast, after a little while a sudden thud happens. Feels like i'm hitting a rock or something. The motor kinda jolts like it wants to tilt up and revs up when it happens. It only lasts for a second and goes away. But it can be very violent and dangerous. What I'm wondering is if it almost feels like it's dropping from forward to neutral (which would explain high rev and sudden jolt). So I checked the linkage to make sure it was tight and not slipping and it seems to be fine, nice and tight. So now I'm left confused. But that makes me wonder if it could be a problem in the gearcase, maybe a bad forward gear or clutch dog. But I wanted some input before I tear into the gearcase. Any ideas?

 

[HighTrim]

Re: 25 hp Evinrude dropping out of forward?

You are describing the classic symptoms of a worn clutch dog, feels like you hit a stump. Unfortunately they are not cheap.

 

[Beek14]

Re: 25 hp Evinrude dropping out of forward?

Well that was kind of to be honest what I was hoping because I have a parts LU for this motor lying around and can swap these out. Could someone describe how the bad clutch dog causes this problem?

 

[jasper60103]

Re: 25 hp Evinrude dropping out of forward?

Well that was kind of to be honest what I was hoping because I have a parts LU for this motor lying around and can swap these out. Could someone describe how the bad clutch dog causes this problem?

Here's a video that explains how it works. The clutch dog have ears that engage into the Forward or Reverse gears. When these ears become worn, the clutch dog can slip out of gear causing the violent reaction you described.

http://www.youtube.com/watch?v=vuAc...=videodirectlink&id=7&feature=player_embedded

 

[Beek14]

Re: 25 hp Evinrude dropping out of forward?

Cool video! So it would be the ears of the clutch dog that would be worn. I am hopefully tearing into the gearcase tomorrow and I will definitely post what i've found. Thanks!

 

[reddaddy]

Re: 25 hp Evinrude dropping out of forward?

does the boat actually plain or does it seam under powered on top end and just fall short. also does it only happen on top end.mine was doing the same thing.turned out i was loading the prop (to much pressure to long).my carb wasn't performing.and the felt like it was on the edge of plaining.rebuilt carb ,boat plained easily,and no more clunk. mine was violent to but nomore.

 

[jimdd810]

Re: 25 hp Evinrude dropping out of forward?

id also check your prop to see if it is slipping before tearing down the lower unit. Draw a line from the outer hub across the prop shaft run it and come back and check your line if it is moved then prop is spun. get a new prop. Usually if a clutch dog is worn out you will get some grinding sounds as well.

 

[Beek14]

Re: 25 hp Evinrude dropping out of forward?

Well top end is very good, it gets the boat right up to plane, this outboard has a lot of power. It is definitely not lacking there, and I've just had the prop rebuilt from the prop shop. That is also perfect. I clutch dog seems to make the most sense. I'll double check before getting into it, but that's kind of what I was thinking it was as well.

 

[Beek14]

Re: 25 hp Evinrude dropping out of forward?

So let's take a look at the clutch dog shall we. The corners of the ears have very little wear, I'm not sure if it's even obvious in the pictures. But one side has a groove wore into it which can obviously seen in the pics. It's not supposed to be like that right? I'm assuming that's a worn clutch dog? Opinions?

 

[wilde1j]

Re: 25 hp Evinrude dropping out of forward?

Sure looks worn to me. There should be almost no rounding on the contact faces. That's why it would stay engaged. Fwd gear is also likely worn as well.

 

[Beek14]

Re: 25 hp Evinrude dropping out of forward?

It might be pretty tough to see through these pictures, but there is some very slight rounding on the corners of the gear ears in about the same spot as the rounded worn parts of the dog. Would that be enough to need a new one.? (I kinda have a feeling that i'll need a new one)

 

[wilde1j]

Re: 25 hp Evinrude dropping out of forward?

There are only two reasons for the symptom you observed: Wear of the gearcase metal or improper shift adjustment. Unless someone messed with the shift linkage, that reduces to just one cause. It doesn't take much wear (usually caused by 'gentle' shifting or just a very old motor).

It's easier to see the wear on the gear ... it's NOT slight!

 

[Beek14]

Re: 25 hp Evinrude dropping out of forward?

So are you saying the forward gear looks alright? It would need more wear than that to be shot?

 

[wilde1j]

Re: 25 hp Evinrude dropping out of forward?

No! Not alright.

 

[Beek14]

Re: 25 hp Evinrude dropping out of forward?

Oh sorry misread your post! Yeah that's what I was afraid of.

 

[jasper60103]

Re: 25 hp Evinrude dropping out of forward?

So let's take a look at the clutch dog shall we. The corners of the ears have very little wear, I'm not sure if it's even obvious in the pictures. But one side has a groove wore into it which can obviously seen in the pics. It's not supposed to be like that right? I'm assuming that's a worn clutch dog? Opinions?

Just an FYI. The groove is not wear. Its a point of reference. The manual states the groove side of clutch dog should face front of gear case. If you need the manual, PM me your email address. I can send you the lower unit section.

 

[Beek14]

Re: 25 hp Evinrude dropping out of forward?

Thanks for the help. When I removed it, it was facing the reverse gear. So that was facing backwards?

 

[jasper60103]

Re: 25 hp Evinrude dropping out of forward?

Thanks for the help. When I removed it, it was facing the reverse gear. So that was facing backwards?

It's likely someone worked on it before and did the cheap fix by reversing the clutch dog.

 

[Beek14]

Re: 25 hp Evinrude dropping out of forward?

ah it's all starting to pan out now. I haven't had the motor for a year, and still have not successfully had it on the water for use. I've gotten through all of it except for this. It's kind of a bummer because i've put a lot of work into this outboard, and I know it runs great! So I thought everything was good until I wound up to high speeds. It doesn't really seem like something you can test without having it running on the boat.

 

[wilde1j]

Re: 25 hp Evinrude dropping out of forward?

That's the only way to test a motor. You can't tell much running on a hose or in a barrel, other than the motor will run.