Old Evinrude 4HP Lightwin

[agesilaus]

I picked up a 12 ft jon boat, trailer and 4 HP Evinrude. I mainly got it to allow us to get to some of the local springs on the Santa Fe and other local rivers that don't have land access.

The motor is pre-1970 I think but is excellent shape functionally and cosmetically. However it has some mystery controls. Besides the throttle lever and choke there are two knobs. One I think I've figured out- it has a RICHER -> label with arrow so I'm thinking it controls the air/fuel mix.

The other one above the richer knob just has four markings: 1,3,5 and 7. One number in each quadrant of the knob. The plate that would have labels for these is gone.

That has me stumped. Any ideas out there?

I assume I should set the air/fuel mix to rich when starting and turn it down to lean once the motor heats up. Is that correct?

The motor starts on the first pull right now. It will stall if I move the mystery knob up from 1 to 7.

Thanks for any suggestions

 

[BRT]

The choke should take care of cold enrichment. I wonder if the 2 knobs are low and high speed adjustments. Many small engines, and almost all 2 strokes have them as screws but now they put limiters on them for emissions. We have to get the limiters off anytime anybody has a carb problem. The other possibility is one is the idle control but I don't think so because in that case moving from 1 to 7 would raise the idle speed.

If the knobs are what we call low and high speed adjustments one will have more mixture effect at low speed and one will have more effect at high speed but they both will affect both somewhat.

 

[Scubadude_LA]

Top controls the slow speed jet on the carb, bottom controls the high speed jet. See below for some plagiarized info.

Initial settings are: Bottom high speed = seat gently, then open 1 turn out. Top slow speed = seat gently, then open 1-1/2 turns.

Setting the high and low needle valves properly:

NOTE: For engines that DO NOT have a shift selection, obviously there is no NEUTRAL position. Simply lower the rpms to the lowest setting to obtain the low speed needle va /lve adjustment.

(High Speed) Start engine (it will run pretty rough), shift into forward gear, take up to full throttle. In segments of 1/8 turn, wating for the engine to respond between turns, start turning in the bottom high speed needle valve. You'll reach a point whereas the engine will either start to die out or spit back (sounds like a mild backfire). At that point, back out the needle valve 1/4 turn. Within that 1/4 turn, you'll find the smoothest setting.

(Low Speed) Slow the engine down to where it just stays running. Shift into neutral. Again in segments of 1/8 turns, start to turn the top needle valve in. Wait a few seconds for the engine to respond. As you turn the valve in, the rpms will increase. Lower the rpms again to where the engine will just stay running. Eventually you'll hit the point where the engine wants to die out or it will spit back. Again, at that point, back out the valve 1/4 turn. Within that 1/4 turn, you'll find the smoothest slow speed setting.

 

[agesilaus]

Thanks to both of you! I'm going to print this out. I looked at an even older Evinrude yesterday and figured out that the slow/fast speed as suggested by BRT. But that didn't tell me what to do with them.

 

[Scubadude_LA]

No problem, glad to help. I have a 4hp LightTwin myself, run it completely out of fuel when you store it seems very reliable.

BRT has a great point on the damn emmsion stuff. I have gas trimmers etc now with the stupid anti-tamper jet screws and I end up throwing away the trimmer that won't run right, then go buy another one made in china and shipped over here on a heavy fuel oil burning cargo ship when all I need to do is turn a screw 1/6 of a turn on a device that burns a total of about 1 gallon of gas annually. How bout that for emissions?? Just venting

You cave diving with that boat??

 

[agesilaus]

"You cave diving with that boat??"

Not yet, I haven't quite got to 25 dives yet. I plan to take caverns next fall/winter when I get well over 50 dives. But there are a lot of OW springs around here that you can't get to by land. I think we will have to dive off the shore not off this boat tho, it's probably to unstable to dive directly off of. I do have a 21 foot Mirage sail boat that we are going to get back into the water and use for diving offshore.