Home › Forum › Ask A Member › Random questions about my 1958 Johnson RDS 20
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crosbyman.
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November 19, 2024 at 3:24 pm #292180
As I work through bringing this old motor back to life I have a few questions on the work I have done and also propeller selection. I went through the carb with an OEM carb kit. It still had the float needle without the clip in it. Is it worth it to order a newer style with the clip? I assume the previous design had issues sticking more compared to the new design?
I also went through the ignition, new coils, wires, points condensors and am getting weak spark on the top cylinder according to the spark testers that light up. Before I go double check all my work, would there be common culprits for this?
Lastly is prop selection, I really have a hard time trying to decipher which one to get. The 35hp motor will be going on a 14′ runabout aluminum, a very light boat. Our lake is 10 miles across and we would plan on longer trips with the boat so top end would be appreciated more than accelleration. Any suggestions here?
Thank you
November 19, 2024 at 10:34 pm #292193the clip is usefull but if I am not wrong it was the help out the sticky teflon coated needles come back down to let fuel in … some folks like to keep and reuse the older non teflon needles .. just make certain the passage is clean.
as to weakspark reclean the points and if no improvement switch condensers as a test.
what is the Kohms value on your 2 coil secondaries . for some reason I prefer the ones with 4-8 kohms max.
prop.. it depends… motor is a 4500 rpm engine so prop needs to matched to the load
amazon has cheap RPM readers…you can use to confirm the best choice or… just check what you have now !
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November 20, 2024 at 11:22 am #292204At the link below, scroll down until you find your motor in the left column – be sure it says “pin Drive”. You will find props up to 14 inch pitch. Higher pitch = more speed as long as the load isn’t heavy enough to make the motor lug down. Note the “Application” column with abbreviations defined at the top of the chart. For your light boat, you probably want the 13-1/4 or 14 inch pitch. I’d start with the 13-1/4 because the 14s are often used for dual motor setups. Like Crosbyman said, using a tachometer to see where you are at is best way, but not everyone has several props laying around to try out.
https://propcomarinepropellers.com/pages/evinrude-johnson-propeller-specifications
Here is a link to cheap, easy to hook up and use tachs Crosbyman mentioned:
November 20, 2024 at 11:57 am #292207Soft needle tips need the clip. Plain metal tipped needles do not need the clip.
13-1/4 prop will be fine. 14 is just too much for a 35hp on all but the lightest boats and loads.
November 20, 2024 at 12:17 pm #292208Unless you own an oil company you probably will be running it a lot on fuel saver (Cruise) throttle anyway.
November 20, 2024 at 12:35 pm #292209hum… kids skiing should be good for 4 gal/h plus oil !!!
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November 21, 2024 at 8:02 am #292225Thanks all for the responses. The coils I put on read right around 8k each. My first step will to clean the points, if that doesn’t work I will take the coil back out and re-seat the plug wire again.
I had no idea hooking up an rpm gauge would be that easy and cheap. I have one ordered from Amazon now. I also learned they have GPS speedometers, I thought those were pretty neat so I ordered one as well.
For the prop, thanks I have saved the links. Unfortunately the first snow just fell in Michigan so it will be a while before I can water test this thing. So the strategy is to measure rpm’s at WOT with typical load then adjust from there.
For the oil – yes I think the cheapest tcw3 oil I found is from walmart at $20 a gallon. I may have to have the oil truck just stop by my place once a week. 🙂
One more question – when I was replacing ignition components I noticed the timing was off. The carb linkage was engaging about 1/4″ before the line on the throttle cam. I have worked on a couple 50’s 10hp and this is easily adjusted with the adjustment screw. On this motor though, the cam is all the way pushed in and still engages 1/4″ too soon. I’m assuming this should be dead on the line the same time the carb linkage starts to engage?
BTW, this is the project I am working on https://www.aomci.org/forums/topic/1963-mirrocraft-with-1958-johnson-rds-20/#post-292224 and attached is a picture of a 10hp we went through that now runs amazing for my sons boat.
November 21, 2024 at 8:45 am #292228WRONG. There is an upward pointing pointer on the intake manifold, to the left of the carburetor. The throttle should be just ready to start opening when the line on the cam is aligned with the pointer, not with the roller.
November 21, 2024 at 9:35 am #292229Thank you for that. I will check when I get the flywheel off.
November 21, 2024 at 10:39 am #292230if you don’t have the bible (sorry to repeat myself) but if you work oldies u need this book
https://watercraftmanuals.com/outboard/johnson/manuals/johnson-302231.htm
download and print double sided 400 pages + covers all oldies late 40s (TD TNs to mid 60s
Evinrudes & johnsons are cousins anyway see page copy from the bible… 🙂
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