1971 Evinrude 125 - Smoking When Cold

I recently came into possesion of a 1971 Winner 17' Runabout Bimini. It has an original (as far as I can tell) 125 hp Evinrude. The compression in all 4 cyl is OK. There are no obvious leaks, etc. The engine runs great, however, until it warms up it smokes like a WWI trench warfare SMOKE GRENADE!
It idles, runs, powers up, etc. but until it warms up it smokes...Once it warms up it goes back to normal o/b operating smoke. Does anyone have an idea of why it is smoking soo much at start-up?

Re: 1971 Evinrude 125 - Smoking When Cold

The carb float valve may be leaking slightly.Try unhooking the gas line while the engine is off.

Re: 1971 Evinrude 125 - Smoking When Cold

gotta say rebuild the carbs and make sure mixture of oil is right usually 40:1

Re: 1971 Evinrude 125 - Smoking When Cold

This should be a simple fix.

99% of the time it's the choke solenoid warm up circuit. The choke stays somewhat closed until the motor heats up. The fix is to disconnect this function. It's not needed and later units eliminated it. The choke will then be only on or off - controlled by your choke switch - nothing in the middle.

The choke solenoid - the thing that clicks when choke is applied has 3 wires. An upper black that is an obvious ground, plus 2 wires coming out near the bottom of the solenoid.

As I recall both bottom wires only differ by a stripe. I don't have a schematic for it, but I know Joe Reeves does and knows this Mod every which way from Sunday.

The repair will remove one wire at the terminal block and add it to another terminal. Both wires involved are from the solenoid.

I can walk you through it, but it'll get a bit wordy as I don't have the color codes.

The "repair" itself takes about 1 minute.

Let's see if Joe can jump in here and I'll also look for the diagram.

Re: 1971 Evinrude 125 - Smoking When Cold

Here it is.....


(Temperature Actuated Choke Solenoid Conversion)
(J. Reeves)
Various OMC engines that were manufactured in the later 1960s thru the early 1970s, for example the 1969 55hp Evinrude/Johnson incorporated a dual stage choke solenoid...... easy to identify as they have two wires leading to the solenoid, one purple/white, one purple/yellow.

The purple/yellow is attached at the engine wiring terminal strip to another purple/yellow wire that led to a heat sensor. The initial stage, with the key ON, (purple/yellow), when cold, would keep the choke pulled in half way until the engine warmed up, at which time it would release and open the choke butterfly.

The second stage (purple/white) is attached to another purple/white wire at the engine terminal strip which leads to the choke switch. When the switch was engaged, the choke closed etc.

The problem with this setup is that as the engine got older, the thermostat acted up, water pump became weak, whatever, the heat sensor failed to operate properly and the choke would not release from that half closed position. This would cause the engine to run in a rich fuel mixture condition (flooding, loading up).

The cure to this problem, via a service bulletin from OMC was to remove the solenoid purple/yellow wire from its original location and connect both of the solenoid wires (purple/yellow & purple/white) to the engine wiring harness purple/white wire at the engine terminal strip.

The above change would allow both solenoid wires to be energized when the choke switch is engaged, pulling the choke butterfly in firmly..... and only when the choke switch is engaged.