Is this dog ok? Johnson 1955 RD-17 25hp sneezing & gears

[osaga]

1955 RD-17 Sea Horse 25hp

I had an issue with the engine "sneezing" and jerking violently under load and at idle. I believe the issue loosened the upper shift linkage because the forward gear wouldn't engage and left me stranded yesterday up the Willamette. With the shift linkage coupler access panel off, using some needle nose pliers, I have about 1/4" worth of play on the upper shift rod. I'm guessing that's too loose? I'm planning to take the powerhead off to tighten whatever shift linkage is hidden under the motor. While I wait for gaskets in the mail, I've decided to re-seal and inspect the lower unit, which leads me to this question:

Is the shift dog and forward gear in the attached photo still usable / within wear tolerances? I don't mind buying the dog on eBay ($14), but the forward gear is $51.

Regarding the sneezing. I've read that it can be caused by: 1. Dirty points 2. Improper fuel/air ratio due to throttle cam position. 3. Vacuum leak in the carburetor, possibly at slow and high speed needle packing washers.

This sneezing began after I rebuilt the magneto AND cleaned the carburetor. When cleaning the carb I was pretty thorough and removed and replaced the packing washers for the high and low speed adjustment needles. I'm hoping that I just need to re-pack them to cure the issue. However any other insights would be appreciated.

Cheers

 

[Joe Reeves]

The shifter dog is shot... replace it.

The gear would cause a new dog to wear quickly..... have a machine shop dress up the worn areas evenly on both worn lobes , that is if their charges are less than a new gear... otherwise, replace the gear too.

The jerking violently you speak of at a high rpm was due to the engine jumping out of and back into gear.

The condition/wear that exists on that dog is usually caused by shifting into gear slowly, thinking one is taking it easy on the lower unit parts... nothing could be further from the truth as that allows the lobes on the dog to clash many times with each other before the dog lobes actually engages the lobes of the gear.

The proper manner of shifting into gear, whether it's forward or reverse is to SNAP it in gear as fast as possible. Think about it!

NOTE: Examine the new shifter dog thoroughly. Some can be installed in either direction... HOWEVER... many must be installed in one direction only. There may be small print inscribed stating "Prop End"... or there may be score marks on one face of the dog which indicates the forward end of the dog. A shifter dog so marked and installed backwards will have the unit jumping out of gear immediately even if everything else is perfect.

The spitting back condition is normally due to a lean fuel setting of the carburetor... wrong jets, jets installed wrong, adjustable needle valve adjusted improperly, air leak at carburetor to intake manifold gasket, something of that nature.It is not an ignition problem.

 

[harringtondav]

I'd go with the $14 dog. The gear looks amazingly great for a 59 yr old gear. The clutch teeth in the gear look good enough to fine. That dog doesn't owe you a dime. The wear on the dog's teeth is the issue. Dog and gear clutch teeth are 0 degree up to 6 degree positive rake for hold-in under load. That dog is worn negative rake to a point where it won't hold.

 

[flyingscott]

I agree with Joe repair or replace that gear or you will have more problems.

 

[osaga]

Thanks for the replies. Joe I'm hoping you're right that it's just been jumping out of gear the whole time, I'm not sure why I assumed the jerking was a misfire.

The parts catalog only shows a part number for the gear and pinion group, fortunately I came across the individual part numbers by chance and found some on ebay much cheaper.

Part numbers in case it's helpful for others:
375816 - gears assembly in 1955 parts catalog
375759 - forward gear with brass bush pressed in
302517 - reverse gear no brass bush (bushing floats, is not pressed)

Parts catalog:
1955 Johnson 25 HP RDE-17 Parts.pdf

I found this cheap one but it's covered in rust or old grease, I can't tell:

I'll report back after I get this back together. Thanks again!

 

[F_R]

As you already know, that slop in the shift rod must be corrected, or you won't have fixed anything.

 

[Joe Reeves]

As you already know, that slop in the shift rod must be corrected, or you won't have fixed anything.

Osaga.... The above quote from F_R is Gospel of which I am in full agreement with! That needs to be taken care of for sure or your problem will be repeated.

 

[lindy46]

Thanks for the replies. Joe I'm hoping you're right that it's just been jumping out of gear the whole time, I'm not sure why I assumed the jerking was a misfire.

The parts catalog only shows a part number for the gear and pinion group, fortunately I came across the individual part numbers by chance and found some on ebay much cheaper.

Part numbers in case it's helpful for others:
375816 - gears assembly in 1955 parts catalog
375759 - forward gear with brass bush pressed in
302517 - reverse gear no brass bush (bushing floats, is not pressed)

Parts catalog:
1955 Johnson 25 HP RDE-17 Parts.pdf

I found this cheap one but it's covered in rust or old grease, I can't tell:

I'll report back after I get this back together. Thanks again!

Looks like a little surface rust - should clean up. $10 is a steal. Go for it.

 

[osaga]

I finally got all the replacement parts I ordered from various eBay sellers to put the lower unit back together. I ended up replacing the clutch dog, forward gear, all the seals, impeller, and the brass drive shaft sleeve/bushing because the old one was a tad loose/sloppy on the drive shaft.

Now that it's back together, it is very difficult to rotate. I can't rotate the drive shaft by hand, but I can rotate everything by grabbing the propeller The prop shaft and gears turned smoothly prior to inserting the drive shaft. I had to tap the drive shaft into the lower unit gear splines gently with a hammer. Is it normal for the drive shaft to be so stiff/difficult to turn? My fear is that either the drive shaft or lower unit may be slightly bent, causing a lot of friction on the drive shaft where is meets the new brass sleeve/bushing located just below the impeller housing.

If this is normal, I'll just run it and hope it loosens up over time. If not, I'll disassemble and inspect, which will be a pita due to the 3m sealant I just used.

Planning to take the powerhead off and tackle the sloppy shift linkage issue this weekend.

Thanks again

 

[flyingscott]

Sounds like the gears are binding look to them.

 

[F_R]

Had to pound the drive shaft in with a hammer???? Almost a sure bet the gearcase is bent.

EDIT: Take it apart and take the gearcase to a machine shop and have their QC guy check the parallelism of the top and bottom surfaces. Easy job for him.

 

[osaga]

Damn. I'm thinking the lower unit housing is very slightly bent. Which would explain why the old drive shaft bushing was worn, probably to about 1/32" or an inch worth of slop. Impossible to tell visually, so I'll take it apart and take it to a machine shop. ugh

 

[racerone]

Never heard of having to use a hammer on one of those.-------Something is wrong here.

 

[osaga]

I took it to a reputable machine shop and the owner, who has fond memories of working on his childhood Elgin outboard, essentially told me the following: The lower unit housing is cast aluminum and unlikely to have been bent without cracking and that the new drive shaft bushing needs to be worn in. I asked if they could check to see if the machined top and bottom surfaces are parallel, and he said that that wouldn't necessarily determine the issue. He said that it will eventually loosen up with use. I asked if I should put the old brass drive shaft bushing back on, and he said he wouldn't bother doing that.

I guess I'll just put it back together, re-seal it, and see what happens

 

[F_R]

Well the factory service manuals certainly think they get bent. Ever see a guy launching a boat off a trailer without tilting the motor? Whole dadgum boat jamming the lower unit into the mud or rocks.

 

[F_R]

They bend in the skinny portion above the "bullet". Makes the case "curved". Preferred method of checking is on a surface plate and height gage (what the machinist would have done, if he would). You can also check it on a drill press table, using the spindle as a gage, but that method is subject to errors.

 

[racerone]

We will now get comments from those who will say----" how could those big parts be bent " ----I am waiting.

 

[osaga]

Spent the last couple hours working on it. Using a tape measure on each side I get near perfect measurements, or as perfect as a tape measure can be. Surprising, because I've definitely hit the motor on the ground a few times backing up my driveway.

I went ahead and pulled the top oil retainer to access the shaft bushing and found that all the friction and binding was occurring at the bushing. The new one is so tight against the shaft that it's difficult to turn by hand. That bushing also directs the shaft about 1/8" off center from the pinion gear splines. This offset is parallel to the prop shaft, which means the lower unit isn't bent side to side at least, but perhaps front to back. I went ahead and tried the old bushing which has about 1/32" play in it, and everything feels very smooth with no major friction. I'm going to just re-install the old one.

The machinist told me that Mercedes used to age their cast aluminum engine blocks 10 years before machining them. Apparently aluminum becomes denser or less malleable just with age.

 

[racerone]

No-----Aluminum casting have a lot of internal stresses.-----If not properly treated / stress relieved before machining you end up with problems.----Used to work in a shop where aluminum parts were " aged " by putting them on the roof in spring.----Parts warmed up during the day and cooled off at night.-----Parts were there for a month or more , no labour costs involved.-----Also used a freezer and boiling water in stages of this aging / stress relieving process------.And there are many different aluminum alloys and not all of them behave the same.

 

[F_R]

At least you acknowledge that the case is distorted and the bushing and pinion are out of alignment. What you do about it is up to you.

Over and out.