Mix lower unit gears and gearcase halves?

[1946zephyr]

Yea, I believe 1956 was when they changed the gears in those. They also did in many other models as well

[olcah]

Holding the pinion and gears loose in my hands they do appear to mesh OK. The pinion is from a 1954 Evinrude Big Twin and the gears are from 1956 RD18. Thank you for the heads up.

[garry-in-michigan]

The 375861 gear set was used in Evinrude Big Twins through 1956. The 376996 gear set was used in 1957 and later Big Twins. I assume that would also be true of RD Johnsons. . . 🙂

[1946zephyr]

quote Garry in Tampa:

The 375861 gear set was used in Evinrude Big Twins through 1956. The 376996 gear set was used in 1957 and later Big Twins. I assume that would also be true of RD Johnsons. . . 🙂

I believe so too, sir.

[olcah]

Thank you Garry, Checking the 1957 Johnson parts list confirms the gear changes you identified. Looks like there was a lot of change to the gearbox in 1957. The 1957 parts list even includes adding a needle bearing for the drive shaft. That makes the 1955 and 1956 Big Twins somewhat unique.

[dan-in-tn]

According to the way I am reading the 1970 Johnson Common Parts Reference Guide the only difference between #375861 gear set for RD-10 thru 19, RDE-16 thru 19M & RJE-18 was the pinion gear #375835 with tapered bearing, shim and cup.
The RD-19, RDE-19, & 19M & RJE-19 took gear set #376996 with the only thing different being the pinion gear #308692. Forward gear #375759 & reverse gear #302517 stayed the same in both gear sets. The #308693 pinion gear dropped the tapered roller bearing and went to the larger gear stub with full radial bearings. That newer pinion gear is used into the 1970s 40hp according to the guide.
Just another tip: the forward gear & reverse can be swapped in position if the forward gear bushing is pressed out (a little heat helps) and pressed back into the reverse gear. The reverse gear bushing is easily removable. Once this is done the gears can continue to be used in spite of shifter wear at the lugs. Similar to turning the shifter around.
I just finished building a 1955 Big Twin with these fixes. The only odd thing I ran into was a small driveshaft bearing under the water pump. It was pressed into the housing. Luckily I had a bearing of same part number to replace it with. I think it was a Torrington 1012-BH. I have not found this bearing illustrated in my parts break downs, but don’t have every book?
Any comments appreciated?

Dan in TN

[vintin]

If the shift dog is reversed in orientation it presents it’s same surfaces to the gears. Like Dan said the bushings can be pushed out and swapped and this puts the lessor worn reverse gear in the forward position and vice versa. Unfortunately the shift dog still contacts the gears on their already worn location. Of course the reverse gear and dog contact area is most likely less worn then the forward gear and dog interface. It would be neat if it didn’t work out like this but I’m pretty sure it does.

I’ve only done this on one motor foot, a 1957 RDE.

Later prop shafts were drilled and had two ball bearing and a spring that indexed into a dog designed for such.

[dan-in-tn]

Yes it does & you can drill the older shaft for the detent spring, balls, & later shifters. Works out real well. The later shifters have much larger lugs, but of course the edges are what has to be taken care of. The detent springs do help the shifter pop into gear and stay there.
As mentioned in earlier post, if you put a 2 to 5 degree lead in angle on the shifter & gear lugs then old gears can be repaired. It is time consuming to do this by hand. It is important that both shifter lugs pull evenly against the gear lugs.

Dan in TN

[vintin]

Hey Dan any chance of you having the OMC jig for guiding the drill when drilling the shaft?

[wbeaton]

I have interchanged gear sets from 25-30-35 hp and into the early 40 hp OMC’s in several motors. There are a few differences, but they will swap. I often swap out the keyed propshafts for the threaded propshafts so I can use a threaded prop nut. My 1954 25 hp has a 1957 35 hp gear set minus the pinion, of course. I’ve also only had one mismatched skeg section that wouldn’t mate.

Wayne
Upper Canada Chapter

uccaomci.com

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