Topic: 1955 Big Twin – Antique Outboard Motor Club,Inc

This topic has 11 replies, 5 voices, and was last updated 6 years, 10 months ago by frankr.

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June 10, 2017 at 7:37 pm #7293
hmai
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Guys a few questions about my bigtwin.

1. Has anyone had any luck with the o rings to seal the lower unit craddle screw? Not sure of the proper name but as I snug it down it just pushes over the screw. Lower unit has been completely sealed but noticed some minor seeping after it has been used for a month now.

2. Is there any way to adjust the shift linkage on these? Out of no where was loosing foward gear. Lower unit looked new, no signs of any wear when I resealed and ran like new for the last month and a half. Very careful to replace all shims/washers exactly how it was when taken apart. Topped lower unit off last night and seen no signs of any leak/water besides the note above. Lower unit fluid appeared to remain full. With the lower unit dropped it shifted as expected. I am hoping i simply didn’t snug the shift coupler enough after the reseal. Just thought i would ask if anything else i should look for before i drive another hour to the lake. Ran great in barrel.

Aomci member
June 10, 2017 at 7:47 pm #59419
chris-p
Participant
1. The gaskets seal better than the o rings. As you noticed, the o rings simply slide out when tightening the pivot pin. Coat both sides of gasket with 3M 847, and you are good to go.

2. There are adjustments, however, if the lugs on the clutch dog, or gears are worn, you are just prolonging the inevitable. The wear can be hard to see, if you don’t know what to look for. Also, ensure that at the shift rod coupler, the detents in the rods are perfectly aligned with the holes in the coupler. There is then adjustment to do behind the shift handle. You loosen the bolts, and adjust so that it is centered between engagement in forward and engagement in reverse. I favour forward just a touch. Not a great explanation, but ill try to post a picture to better explain.
June 10, 2017 at 10:31 pm #59431
frankr
Participant
US Member
The o-ring is intended for the newer pivot pins with a groove under the head. The ones with a flat under the head take a gasket.
June 11, 2017 at 3:41 am #59450
garry-in-michigan
Participant
Lifetime Member
A fine looking outboard.There should be o 2" hole in the front lower motor cover. (Under the carboretor) They originally had a quarter inch hole and struggled to get enough air. As was previously posted, there is a bit of an adjustment at the shift lever. A tendency to jump out of gear can be helped by turning the dog clutch end for end. Since reverse isn’t used as much, that end is usually in better shape. Ware happens when the the edges of the dogs don’t quite catch and beat over the sharp edges. This reduces the area of contact which accelerates the ware. The secret to long shifter life is slow motor speed and fast shifting. Always shift into gear with a snap. . . 🙂
June 11, 2017 at 7:05 pm #59475
hmai
Participant
Thanks guys

I have done a number of these and am sure the clutch dog is fine. None of the glossy edges u expect to see on worn dog ears. I doubt the motor has more than a few hours on it. Prop and drive shaft was perfect not even a scratch from the bearing seats. Tested the adjustment and coupler ran in barrel for a 1/2 hour in and out of gear.
Usually run at 2/3rds throttle, plenty to put my 16ft utility on plane.

Now to test under load.
June 11, 2017 at 7:50 pm #59477
frankr
Participant
US Member
If the model number is RD-17S or RD-17R, pull the powerhead and replace the lower main bearing seal. Those seals were garbage and destroyed many a motor by letting water into the crankcase. RD-17 (no S or R) is ok.
June 11, 2017 at 8:43 pm #59481
hmai
Participant
It is a S. Thanks
June 11, 2017 at 8:44 pm #59482
hmai
Participant
Anyone know of the part number for the pivot pin gasket?

All i can find is the O ring.
June 11, 2017 at 8:55 pm #59483
frankr
Participant
US Member
Gasket is part number 304083. But it has been a long time since I’ve ordered one. A hole punch through a piece of gasket material and trim around it with a pair of scissors will make one.

Picture is of a 12/15hp, but same seal was used there
June 11, 2017 at 9:27 pm #59484
hmai
Participant
Frank,

Thanks again, would you happen to know the part number for the main bearing seal? The main bearing seal will be a winter project for me. I have been using this one every weekend.

Cant imagine how many of these u have worked on.
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