66 Rude 40HP Carb question

[spratt]

I have successfully taken my boat out twice now, and it ran like a dream both times. However, on the second trip, after running around for about an hour, we were returning to the dock, and when I took it down to low idle to tie up, the engine died. It would only restart after choking it and then ran roughly like it wanted to die again, and it did after taking choke off. I crippled back to the dock, and when I got it home, I removed the cowling, and found a screw, possibly the Mixture Screw right above the carb, almost falling out. I pushed it back in and the engine started and ran fine. Why would that screw come out? Does it thread in, or just ?? I haven't had a chance to look it up in the manual yet, and since there are so many geniuses out there with a sure ready answer, and I am at work, it seemed to be the best thing to do is ask...so...???

 

[AMD Rules]

Re: 66 Rude 40HP Carb question

The screw you mentioned is likely the low speed needle valve, that is threaded into a hole in the face of the carb. Typically that is screwed in all the way GENTLY, and then backed out 7/8 turn or so to provide a smooth idle.<br /><br />In order to prevent it from coming loose during operation, you need to tighten the packing nut (hex nut) which holds the compression packing tighly around the valve screw. That needs to be tight enough to let you turn it, but not loose enough to allow it to vibrate out over time.<br /><br />Ideally you want to have about 650 rpm at idle, with the boat in gear. Adjust for smoothest performance, while keeping it as slow as possible to avoid undue stress on the gears.<br /><br />If you're lucky enough to still have the indicator knob screwed into the end of the valve screw, then reposition it after you have found the 'sweet spot' so that it points straight up. That gives you a point of reference to go by. Adjust lean or rich accordingly as required.<br /><br />Hope this helps.

 

[JB]

Re: 66 Rude 40HP Carb question

That "screw" is an adjustable jet needle, spratt.<br /><br />The brass fitting that it goes through should be compressing packing to keep it stable. Check that the packing is still in there and tighten up the brass fitting until the jet needle can still be adjusted but is firmly held in place when the engine is running.<br /><br />Good luck.

 

[spratt]

Re: 66 Rude 40HP Carb question

Ahhh, the plot thickens...the screw goes in and I can feel the "packing" but there is no brass nut to tighten down on it Therein is the problem...and no, AMD, the indicator is probably LOOOOONG gone...I have owned this boat for two weeks now, and had it out only twice. So I guess I will be looking for some used parts, and a carb overhaul kit...

 

[AMD Rules]

Re: 66 Rude 40HP Carb question

When I first had my motor, a '69 40hp Lark I had a very similar experience where the needle almost fell out. You will need to get a packing nut in order to keep it from happening again. Make sure you check down below, the nut has probably fallen out and may be under the power head. I found a few surprises when I opened up the mid-section. It is a nice place for fallen items to collect over time.<br /><br />Like you, my indicator on the end is looong gone.

 

[spratt]

Re: 66 Rude 40HP Carb question

Yeah, I will be overhauling the lower unit soon adn will have it all open then...no telling what is in there, you are right...