1957 Johnson RD-19 Siezed Lower Unit

Hi,
I am new to the vintage restoration of OMC's but so far I am enjoying what I am doing. I have 2 RD-19 motors. One with electric start and one without. Of course I got the one without the electric start running great, but the electric start motor is giving me headaches. First problem is I have no spark so I am replacing the coils, points and condensors. Once that is done I expect for the thing to start up with maybe a carb cleaning or not.
The problem is the motor was sitting for the past several years with water in the lower unit. The lower unit is siezed. I pulled the unit out and the transmission gears still look like they are in great shape and spin freely, but the bushings and bearing for the drive shaft are rusty and stuck in the lower unit. I was wondering if anyone has any good advice on how to loosen these things up so I can get them out and replace them, or is it a lost cause and scrap the lower unit and but a new one.
If I go the second route and buy a used lower unit what other models will fit onto my powerhead?
Thanks,
Brode

Re: 1957 Johnson RD-19 Siezed Lower Unit

I would say make a mix of 50/50 acetone and atf brush it on the parts and keep doing so for a week. Air blow off the dirty stuff and apply new each day, then tap and try to turn the shaft a little at a time. Patience is the key.

Re: 1957 Johnson RD-19 Siezed Lower Unit

If the motor without electric start runs great, then I would just transfer the starter and stuff over to it and either fix up the other one at your leisure or use it for parts.

As far as a replacement lower unit goes, you can get a lower unit from the Big Twin/Rd's form 1956 on up to work on that. The 1955 and older 25's would fit, but the gears are smaller and won't hold up to a 35hp powerhead. The 28's and 33's have lower units that will work. The lower units from the Super Quiet 35's and 40's may or may not work, because of the dual water tube set up, so you would have to change the waterpump assembly. They built the single wall style exhaust housing on the big twin style motors clear up into the 70's, up to 40hp and that is the style of lower unit I would stick with.

Re: 1957 Johnson RD-19 Siezed Lower Unit

The Super Quiets will NOT work - different bolt pattern.

As for the bearing race - it'll come out with heat to the housing. It is a press fit, and the aluminum housing expands more than the steel race. A propane torch to the outside of the housing near the bearing race, and it SHOULD fall right out with some gentle tapping of the housing on a wooden bench. Might be able to find a banged up unit with a good race for cheap... Lightly grease the rollers with vaseline or assembly grease to hold them in place while you install the pinion gear.

Re: 1957 Johnson RD-19 Siezed Lower Unit

Cool Avitare Chinewalker. Is that a Mark 20H? Or Mark 25H? The Mark 25's is one of my favorite Mercs.

So, it looks like you'll want to stay with the lower units from the old single wall 30's and 35's till 1958 and the later 28's, and 33's. I found that the later 40's, 1969 and later had the single wall style mid section, but the drive shaft is a little different, where it goes in the powerhead, so watch out there. If it does work, you'll need to use your old drive shaft.

Re: 1957 Johnson RD-19 Siezed Lower Unit

Where are you located? If anywhere near me I can help you out. If not, post a wanted ad on the webvertize of the aomci.org

Re: 1957 Johnson RD-19 Siezed Lower Unit

Thanks for the advice. I little bit of soaking in PB and then some heat with gentle persuasion loosened everything up. Now to buy the new bearings and put it back together.

Brode