1976 Evinrude 25hp Lower unit pinion gear trouble

[BTF112989]

Hello! A few months ago I was driving my 25hp motor around on the lake when it felt like it was going too slow for the engine speed. I immediately stopped the engine and used my trolling motor to get back to the boat ramp. I assumed it was bad gas or something, but I had always noticed a drop or two of gear oil under the engine after I would store it for about a week. I always kept an eye on the oil and I had noticed it got milky a little too fast. So after this incident happened, I decided to drain the oil out and see how it looked. When I drained it, one drop of oil and 2 drops of water came out. BASICALLY NO OIL. I filled it up and drained the next batch of oil too. It came out black with a silver sheen to it but with NO chunks of metal in the LU oil. I'm assuming I just ruined my lower unit, but I decided to just try filling the lower unit back up with oil and see if it will work(doubtful). I launch my boat and try and shift it into forward. Shifts perfectly!!!!!

So now I thought I had just beaten the odds and caught my lower unit just in time before I blew it up. I ran it for another month or so(never going further than a mile from the boat ramp) until one day when I heard a "POP." The engine continued to run but would not go into gear at all. So now I admit defeat and decide I have grenaded my entire lower unit.

I assume I need a new lower unit, but I decide to open it up just because I'm curious to see how much damage I did. When I opened it up, the forward & reverse gears, clutch dog, and bearings looked to be in great shape! I then looked at the pinion gear and it was completely stripped out(picture attached). So I found the pinion gear I need on ebay for $45 dollars.

Since the rest of the gear assembly is in great shape, is there any way I can just buy that new pinion gear and a lower unit seal kit and get back on the water? Do I have to reshim and set the gear tolerances again if I have not disassembled the main gear assembly and I'm just changing the pinion gear out?


Thanks,
Ben

 

[G DANE]

Re: 1976 Evinrude 25hp Lower unit pinion gear trouble

Normally, these gears are run in in sets, but since you can get the pinion gear for a fair price, I se no reason why you shouldnt give it a try. No shimming needed, just put all parts back in the order they were in. Be gentle to it the first 5 - 10 hours. Post your results back, interesting. Be sure no chunks - absolutely nothing is left in your gearcase, or the joy will be short.

 

[G DANE]

Re: 1976 Evinrude 25hp Lower unit pinion gear trouble

BTW change the seals, its easy on that one. I might have a gearcase floating around somewhere, but i know its missing a pinion gear, too, just in case you need anything else.

 

[14ftgrumman]

Re: 1976 Evinrude 25hp Lower unit pinion gear trouble

You have nothing to loose, I don't know about you, but I've spent $45.00 more foolishly. Check the ears on your clutch dog, and the mating tabs on the foreward and reverse gears. If they look good, you are home free. If you remove the clutch dog, be aware that there is a neutral detent. There is a spring with 2 steel balls inside the dog that helps keep it in neutral. Be careful taking it out., very slowly and catch the balls and the spring or you will be chasing them all over your floor. Don't ask how I know this.

 

[F_R]

Re: 1976 Evinrude 25hp Lower unit pinion gear trouble

You have nothing to loose, I don't know about you, but I've spent $45.00 more foolishly. Check the ears on your clutch dog, and the mating tabs on the foreward and reverse gears. If they look good, you are home free. If you remove the clutch dog, be aware that there is a neutral detent. There is a spring with 2 steel balls inside the dog that helps keep it in neutral. Be careful taking it out., very slowly and catch the balls and the spring or you will be chasing them all over your floor. Don't ask how I know this.

Be sure to check the bushings for the forward gear and pinion. They are usually the first thing to go from lack of oil. If they are worn, the gears won't last. The pinion bushing is not replaceable.

 

[BTF112989]

Re: 1976 Evinrude 25hp Lower unit pinion gear trouble

I probably won't remove the clutch dog since the whole assembly looks like its in good shape. I don't want to disassemble it and screw something else up.

F_R, can you explain which bushings you are talking about? There is a washer type disk with rollers on it in front of the forward gear. Is that what you mean by the bushings?

Also can someone else confirm whether or not I will have to relash and reshim the gears in the lower unit since I did not take anything apart in the main gear "bundle" ?

 

[F_R]

Re: 1976 Evinrude 25hp Lower unit pinion gear trouble

I probably won't remove the clutch dog since the whole assembly looks like its in good shape. I don't want to disassemble it and screw something else up.

F_R, can you explain which bushings you are talking about? There is a washer type disk with rollers on it in front of the forward gear. Is that what you mean by the bushings?

Also can someone else confirm whether or not I will have to relash and reshim the gears in the lower unit since I did not take anything apart in the main gear "bundle" ?

Do whatever you want to do. But if you want to do it right and without future failure, you need to take it completely apart and clean everything spotless and give every part a critical examination.

That lower unit was built for over 20 years and I have never seen one with roller bearings in it. The forward gear thrust bearing is part number 302496 and probably is made of sintered metal, though some old ones were brass. Any wear of the thrust face increases the gear lash and will lead to failure. The same holds true for the pinion bushing, which is a bronze bushing cast into the case and is not replaceable.

I can't tell well enough by looking at the greasy pictures, but I'm not so sure the forward gear isn't worn. Again, a new gear against a worn one is asking for failure.

There are no shims or lash adjustments. It is all built in when it was machined at the factory. If the parts are to specs, the gear clearance is automatic.

 

[G DANE]

Re: 1976 Evinrude 25hp Lower unit pinion gear trouble

It could look like it has the roller bearing trust washer, between the forward gear, and the bearing, which means it is not a 1976, but 1978 or newer, are you sure about vintage ? The pinion gear is different for the two gearcases, the later one has needle bearings for the pinion gear as I remember, and the shaft on the gear is longer.

 

[F_R]

Re: 1976 Evinrude 25hp Lower unit pinion gear trouble

It could look like it has the roller bearing trust washer, between the forward gear, and the bearing, which means it is not a 1976, but 1978 or newer, are you sure about vintage ? The pinion gear is different for the two gearcases, the later one has needle bearings for the pinion gear as I remember, and the shaft on the gear is longer.

1978 parts book still shows the bushing and no replaceable pinion bearing. However, 1979 does indeed show roller bearings in those areas.

 

[BTF112989]

Re: 1976 Evinrude 25hp Lower unit pinion gear trouble

I believe I was wrong when I said it was a roller bearing. It is indeed the back part of 302496 that I was referring to. It looked like there was a bearing in between the forward gear and behind 302496. I am fairly certain it is a 1976. It is model number 25652E.

So bottomline, what are my chances for success on this repair if there is at most very light wear on the forward gear and no or possibly very light wear on the pinion gear I purchased?

 

[F_R]

Re: 1976 Evinrude 25hp Lower unit pinion gear trouble

I believe I was wrong when I said it was a roller bearing. It is indeed the back part of 302496 that I was referring to. It looked like there was a bearing in between the forward gear and behind 302496. I am fairly certain it is a 1976. It is model number 25652E.

So bottomline, what are my chances for success on this repair if there is at most very light wear on the forward gear and no or possibly very light wear on the pinion gear I purchased?

It is a try-it-and see situation. It may last for years and it may not. The biggest problem is the wear is not from each other and won't match. Bearing wear is just as important, or even more important than the gear wear.

If you were paying me as a pro to do the job, I wouldn't use any worn parts. However, since it is a DIY project, like somebody said, what have you got to lose?

 

[BTF112989]

Re: 1976 Evinrude 25hp Lower unit pinion gear trouble

I understand what you are saying exactly. I received my pinion gear off of ebay today, and it looks like it has been lightly used before (some of the finish is worn off of all the gear teeth & it has a slight gear oil smell). So, I do not think it is brand new. Do you think I have a better chance now that the pinion gear I have received might have been broken in some already? The pictures are not the greatest, but I'm trying to show the wear on the new gear. The black areas are the non-worn areas, and the bronze-looking areas are the worn areas.

 

[R.Johnson]

Re: 1976 Evinrude 25hp Lower unit pinion gear trouble

Beside's the gears, take a look at the upper pinion bearing. That gearcase ate a glass hard pinion gear. Things had to get a little crowded in there.

 

[Tim Frank]

Re: 1976 Evinrude 25hp Lower unit pinion gear trouble

Do whatever you want to do. But if you want to do it right and without future failure, you need to take it completely apart and clean everything spotless and give every part a critical examination.

^^....100%

 

[BTF112989]

Re: 1976 Evinrude 25hp Lower unit pinion gear trouble

Where is the upper pinion bearing located inside the lower unit?

 

[84 johnson]

Re: 1976 Evinrude 25hp Lower unit pinion gear trouble

You have nothing to loose, I don't know about you, but I've spent $45.00 more foolishly. Check the ears on your clutch dog, and the mating tabs on the foreward and reverse gears. If they look good, you are home free. If you remove the clutch dog, be aware that there is a neutral detent. There is a spring with 2 steel balls inside the dog that helps keep it in neutral. Be careful taking it out., very slowly and catch the balls and the spring or you will be chasing them all over your floor. Don't ask how I know this.

Your comment may have answered a question of mine regarding my 84 johnson 25hp.
Is the spring detent located within the clutch dog? If the clutch dog is not removed from the prop shaft, the spring detent will remain in place? Is this correct?