RDS-20 restoration update

[rebars1]

(see my previous posts for history) 1958 Johnson RDS-20 35hp project. I was able to get the sparks equal and strong on both cylinders, and it is running more smoothly now. However, I am still getting unburned fuel coming out from somewhere below the powerhead. I know there is a bypass valve that releases extra fuel from the crankcase at low speeds. Could this be the source of what I am seeing (running on muffs?) Does this go away at higher speeds, or is it just not noticable when under way on the lake? I can't see the actual hole the fuel is dripping out of. I cleaned the valve and re-installed it with a new gasket.

 

[rebars1]

Re: RDS-20 restoration update

Bump

 

[Paul Moir]

Re: RDS-20 restoration update

If it's appearing in the cowling area, then it's not from the fuel drain valve. The fuel drain valve empties out just beside the bottom of the crankshaft, so it drips down the driveshaft and goes out with the exhaust.<br />It's not coming from the oil recirculation hose is it? (the hose that runs from the bottom of the block up to the top)

 

[rebars1]

Re: RDS-20 restoration update

Thanks for the response Paul Moir. The cowling area is dry. The fuel shows up on the flange of the lower unit just below the lower outer cover.

 

[Paul Moir]

Re: RDS-20 restoration update

Hmm, you shouldn't be getting fuel there from the fuel drain either. I'm picturing that the fuel is coming down bewteen the outer cover and landing on the flange, is that correct?

 

[racinmason]

Re: RDS-20 restoration update

Sorry to butt in guys,but I'm having the same problem on the '59 RDS-21 35hp that I'm getting running.It looks on mine like it's running down the inside of the driveshaft tube or the driveshaft itself.There's enough that it pools around the water pump,and then runs out the parting line between the lower unit and the mid section,especially if the motor's up.I have'nt had it running long enough to get the low and high speed adjusted exactly right,but I'm thinking (hoping!)the excess fuel & oil is from a too rich carb - racinmason

 

[R.Johnson]

Re: RDS-20 restoration update

As I recall, there is a carbon seal with an inner O-ring held in place by a spring, and snap ring. This carbon ring may be broken. Are you having to turn out the low speed idle screw quite a ways to keep the engine running? That seal is located around the lower crankshaft.

 

[CATransplant]

Re: RDS-20 restoration update

rebars,<br /><br />How much of this unburned fuel are you talking about here? That could make a difference in the reason you're seeing it.

 

[rebars1]

Re: RDS-20 restoration update

CATransplant: There is not so much fuel that a stream is dripping onto the ground, but enough that the lower unit flange stays covered. I'm wondering if the condition would go away at speeds higher than at idle? The manual mentions that at idle, some unburned fuel may come out and "form a slick on the water", I'm just not sure how much I should be seeing when on the muffs. <br /><br />racinmason: maybe my fuel is taking the same path as yours. I can't see where it's coming from.

 

[CATransplant]

Re: RDS-20 restoration update

I wouldn't worry about this at all. You may be running a bit rich, I suppose, but I'd get it out on the water and do your carb adjustments, and see how it does after all of that.<br /><br />These are rather piggy outboards when it comes to fuel. Further, if you're running this in a barrel, you'll pick up a lot of unburnt fuel and oil from the water surface.<br /><br />Mine does pretty much the same thing, but slowed down after I got the carb adjusted correctly. I just don't worry about it.