Evinrude 140 low on power random sputter at idle

[SilverSS07]

Hey guys. I've got a 1983 Evinrude 140. Has 110 lbs compression on all cylinders and good spark (jumps 7/16's gap on all 4). It had been down on power since I changed the prop (went from 17p to 19p because hub was starting to slip on the 17) and I just assumed it was overpropped. Wasn't reaching high enough rpm, slow holeshot, etc. Then it started sputtering at idle occasionally. I finally got another 17p prop and put it on and hit the water ready to take off fast like it used to and it still didn't. Checked the coils and found one dead. Replaced it and went out again today and still doesn't have the fast holeshot and random sputtering/missing at idle. Sounds like it is spitting back through the carbs. Not sure where to go from here. I got the motor last year and went through it and replaced everything- all fuel lines, rebuilt carbs, fuel pump, water pump, head gaskets, etc. Plugs look good- maybe been out 6 times since new. It ran great until I switched to the 19p prop. I always use non ethanol, synthetic oil (premix), and star tron in every tank. Thanks for the help.

 

[Bosunsmate]

Check timing
do a drop test on each cylinder see if you can isolate it down to a particular cylinder/carb

 

[SilverSS07]

Thanks I should be able to do that tomorrow. I was also wondering if I should do a decarb since it wasn't reaching proper rpm and was also running on 3 cylinders for a bit. Could the exhaust ports be blocked from the extra fuel being dumped in?

 

[Bosunsmate]

Check your primer bulb holds firm with the engine off. If it does then there most likely isnt an excess fuel problem
You can pull out all the plugs and see if any look different

 

[SilverSS07]

Sorry it took a few days the outboard decided it didn't want to start. Bulb is firm when shut off. Both plugs on the starboard side are darker than both plugs on the port side. Timing is good. Drop test had about the same rpm drop with each cylinder disconnected. I took the carbs apart just to check them real quick and everything was good.

 

[SilverSS07]

I took the ohm readings from the power pack. If I read the service manual right it's supposed to read resistance in one direction and infinite in the other. The power pack on the port side read about 25 ohms one direction and 1.8 the other way. Safe to assume this is the problem?

 

[SilverSS07]

I took the ohm readings from the power pack. If I read the service manual right it's supposed to read resistance in one direction and infinite in the other. The power pack on the port side read about 25 ohms one direction and 1.8 the other way. Other pack reads 1.2 and infinite. Safe to assume this is the problem?

 

[SilverSS07]

I took the ohm readings from the power pack. If I read the service manual right it's supposed to read resistance in one direction and infinite in the other. The power pack on the port side read about 25 ohms one direction and 1.8 the other way. Other pack reads 1.2 and infinite. Safe to assume this is the problem?

 

[SilverSS07]

I took the ohm readings from the power pack. If I read the service manual right it's supposed to read resistance in one direction and infinite in the other. The power pack on the port side read about 25 ohms one direction and 1.8 the other way. Other pack reads 1.2 and infinite. Safe to assume this is the problem?

 

[emdsapmgr]

Regarding spitting back thru the carbs. Two possible scenarios. Sounds as if you have the #1 issue: 1. at idle a periodic miss could be a lean condition-commonly known as a "lean sneeze." A miss every few rpm's. This is a lean carb issue-restricted idle passages-not a spark issue. 2. Actual backfiring through the carbs is a much more dramatic symptom. Spark plug wires may be going to the wrong plugs. When you replaced the coil, you may have wired the power pack to the wrong coil.

 

[SilverSS07]

Thanks emdsapmgr. It's definitely not backfiring and the miss is random, sometimes it runs fine and sometimes it seems to miss a little. I double checked the wiring and it's all correct. It did that before and after I replaced the coil so it's not a new symptom. I ordered a power pack yesterday so I'm really hoping that solves the issue. Should be here Tuesday

 

[emdsapmgr]

Check for spark on each plugwire after the engine has run and is well warmed up. Two easy ways: 1. cyl drop test. When the engine is running, pull a spark plug wire off the plug with a set of insulated pliers. The rpm's should drop. Do this with each plugwire. If you pull one plugwire off and no rpm drop occurs, the plug may not be firing. 2. Check for spark when running with an inductive timing light. The flashes from the gun will show spark quality on each wire. Compare all 4. If you find a "no spark" condition, you can swap the dual matching power packs and see if the "no spark" problem moves to the other head.

 

[SilverSS07]

I did a drop test and had a drop on all cylinders. Engine was hot. Also used a timing light and all were equal. I think the problem only occurs under load when on the water but I can't duplicate the problem on the muffs. According to the FSM when connecting the ohmmeter to A and D leads on the power pack I should get a reading of resistance in one direction and infinite the other direction. On the port side power pack I had resistance both ways which indicates a faulty isolation diode. Unfortunately that's about the only test I can perform right now because all I have is a multimeter. The manual states it can cause a rough running engine but doesn't say anything about a loss of power at higher RPM. I'm hoping they're related.

 

[SilverSS07]

Finally got my new powerpack and took her out today. Didn't help. Just for something else to rule out I put in a new set of plugs even though the plugs that were in there looked good. I was on the water and putting the cowl on is a pain to do from in the boat so I left it off. Fired her up and hit the gas and almost threw myself out of the boat lol. Thing flies. So I went back to the dock and put the cowl back on. Took off again. Took off slow again. Looking at the cowl as best I can it looks like the bottom left (port) latch is touching the plug wire where it goes over the plug. The wires are new but I think it's grounding it out. Trying to think of a way (besides electrical tape) to insulate it. Also going to try adjusting the cowl and see if I can gain a little bit of clearance. Anybody ever had this problem before?

 

[jakedaawg]

Pretty common, Just have to route the plug wire so it doesn't hit the latch

 

[emdsapmgr]

A pretty good catch-the cowling latch grouding issue. Hard to detect, unless you run it on a dark night. Those engines came with special clips which would hold the plugwires away from the cowling latches and the block. If you look at a factory parts diagram, you will see these clips, which have a rubber coating on the clamping end. Held on by a water cover bolt, they spaced the spark plug high tension wire away from any metal part of the engine. Some of the part numbers and quantities installed at the factory were: 310439 (1), 310440 (2) and 309332 (5) They also kept the wires away from the heat of the engine. Hopefully your engine still has some of these. Check your factory parts list at: epc.brp.com

 

[SilverSS07]

Yes I still have some of those clips there to hold the wires away from it. I'm pretty sure the latch was touching or very close to the boot on the plug. Even with new wires apparently the spark would still jump. I tried loosening up the 2 bolts on the cowl to adjust the latch and of course even after soaking them in PB Blaster they both broke lol. I guess I should expect that on a 31 year old motor. Either way- I have more room around the plug boot now. I started it on the muffs and it wasn't doing any sputtering and was running smooth like it was with the cowl off yesterday so hopefully that was it. As soon as I can take the boat out again I'll let ya'll know. Thanks for the help!

 

[emdsapmgr]

If you think the spark plug to coil wire is old and may be contributing to the problem, Bombardier makes replacement spark plug to coil wire kits. Part number: 582365. Most dealers stock that part. Might be worth trying one or two on those bottom cyls.

 

[SilverSS07]

The plug wires were brand new. I got zapped one day with the old wires on so I replaced them all last year. That's why I ruled them out initially.

 

[emdsapmgr]

Did you replace those wires with the genuine factory wire kits I referred to?