Johnson RD-17 1955 25 hp Carb Nozzle gasket ?

[outboardnut]

The RD-17 carb I have came with an o ring around the nozzle but if memory serves me correctly on other big twins I have worked on there is suppose to be a cork gasket. The cork gasket is not shown on the part diagram. Does anyone have the part number for the cork gasket?

[seakaye12]

I believe it is the standard OMC “Boss Gasket” PN 0344037. Not made of cork anymore but something similar that does not break down. Interesting that your parts diagram does not show a gasket used there. I recall discussions here about it. Hopefully someone with better knowledge that I will chime in and explain why that is.

• This reply was modified 5 years, 5 months ago by seakaye12.
• This reply was modified 5 years, 5 months ago by seakaye12.

[Mumbles]

The older Big Twin/RD motors didn’t use a gasket in this location. Instead they relied on the machining of the parts to prevent leakage here. Also, any leakage here might not be noticable considering the amount of fuel these motors use.

[adam1961]

There was no nozzle gasket on those motors from the factory. The smaller motors had one to ensure that all of the fuel has to pass through the high speed jet. You can add a gasket, it will just make the high speed adjustment more sensitive. I often add it when I have one in a kit. I don’t have a part number handy. The gasket was in the kits for later engines.

[garry-in-michigan]

The cork gasket was used on the smaller motors at that time. It was thought the amount of leakage could easily be compensated for with the carburetor adjustment on those high horse power gas guzzlers. Not so on the smaller models which used less fuel. A 3 horse without the gasket could run rich with the high speed mixture needle valve screwed all the way in. The lack of this gasket bothered some who used the gasket from the smaller outboards, since all high speed nozzels are all the same diameter. You can put one in, but it is really not needed. The part number was 302984 – that may have changed . . .

• This reply was modified 5 years, 5 months ago by garry-in-michigan.
• This reply was modified 5 years, 5 months ago by garry-in-michigan.

[frankr]

What Garry said, not needed on that motor. IS needed on 40hp motors, similar carb but with fixed high speed jet

[garry-in-michigan]

[/B]There was a service bulletin on this – what was also not needed was the rubber elbow on the air silencer – also the quarter inch drain hole in the lower front motor cover should be enlarged to two inches. This eliminated the air restrictions that limited the horse power to 23. You get back the power with no noticeable increase in noise. ENJOY !

[outboardnut]

well – while waiting for an answer from you guys I found a cork gasket and installed it.Looks like I will keep it in there.

[outbdnut2]

I once added a gasket from a kit for a smaller motor to a 35 HP RD, but had to section it thinner to make it work. That was before I knew it wasn’t needed.
Dave

[reivertom]

That’s what got me started working on my own motors back in the late 70s. I took my ’67 Yachtwin to an “expert” at a local marina to get it running right, and it came back running not much better. When I took it back to him, he said it was too old and just wouldn’t run right because it was worn out……I knew that was BS because I knew the history of the motor…it was like brand new. I took it apart and found that gasket missing, I put one in and it ran perfect. I never took an older motor back to a marina….they just don’t care, but they will still take you money.

• This reply was modified 5 years, 5 months ago by reivertom.

[Author]

Posts