1993 (Rebuilt) 120HP Evinrude, V4 - Rough running only after startup

[dnyelator]

I have a 120HP V4 Evinrude that typically runs pretty good, except after it's set for awhile. When I first start it, it sounds fine, but when I go to open to full throttle it acts as if I've only sped it up just a little over idle. It sounds like it's throttled up, but I'm only going about 5 mph (when full throttle is 30+ mph). I have tried maxing and then backing off the throttle, several times, back and forth and it just refuses to open up. So I'll set it at full throttle and let it putt along, sometimes for 10 minutes (if it's the first time out for the year), and all of the sudden it just takes off. Then it will run great the rest of the day. It's done this for the past 2 years now. Usually when I run it day after day, it will run fine, except for the first day of a trip, but I did have one instance recently where it acted up two days in a row. I treat every tank of gas with Sta-bil. I've recently replaced the fuel line. Does this sounds like maybe a fuel pump or something else? Thanks in advance. Great forum. Have been reading for years.

 

[dnyelator]

Folks - bumping this in hopes that someone that can help will chime in. I am still having this issue. It only happens after the boat has been laid up awhile. Could it be a coil going out, maybe a fuel pump? I just have no idea where to start with this since it's inconsistent and only occurs after a couple weeks being laid up.

 

[ondarvr]

Occasionally a sticky float needle can do this, it will stick after sitting for a while, but once it's loose will work well until not used for a time.

Check for spark when it's acting up, this will tell you where to start looking.

 

[dnyelator]

ondarvr - thanks for the reply! I didn't seem to get an email from your post, so I just thought no one had replied to my post, so SORRY, and THANK YOU! So do you suggest that I pop the top off the carb and replace the float needle? I assume I'd have to buy an entire carb kit, but it would be worth it if it works. So you don't believe it could be a coil or fuel pump problem? I guess I don't think so either since it runs fine once I get past the first 5-10 minutes of idling. I'm not sure what checking the spark will do for me???? In my simple mind I must have spark or I wouldn't think it would run at all???

 

[jakedaawg]

While ondarvr is prolly right it qould not hurt to do the basics.

While issue is occuring do a open air gap spark check, compression test, and fuel sample. Also preform a cylinder drop teat under load while issue is occuring, with insulated pliers pull plug leads off one at a time and report back changes/results

 

[racerone]

?----The ignition system on your motor is not the same as a 283 Chevrolet engine.---On your motor each cylinder has it's own coil.----Best to test for that spark when motor has sat for a few weeks.-----And if it is a carburetor problem you should not be running this motor.-----No fuel going in means NO OIL to the cylinder with the bad carburetor.---Testing will get the answer every time.

 

[Faztbullet]

Agree with racer and which carb are you going to assume is acting up as it has 4 carbs?? More likely a timer base or pack problem....

 

[dnyelator]

Thanks for the responses folks!!! Much appreciated!!! I'm waiting for the OMC oil and new drain plugs to come from Amazon, once I get that back in the lower unit, I'll fire it up and do a spark check and report back. So is it normal for a timer base or pack to only act up once in awhile (which is my case....boat only acts this way after a long layup, runs great once it snaps out of it's funk and then runs good the rest of the trip normally).

 

[interalian]

Usually it's the opposite - electronics malfunction more when warmed up or heat soaked. Another thing to try would be to check connectors when it's acting up - moving cables and wiggling connectors would simulate the vibration that may be acting to make a bad connection OK.

 

[dnyelator]

interalian - my thoughts exactly. Thanks for the suggestion to move the cables around. If this happened all the time, it would be a lot easier to troubleshoot, but when it only happens after a layup, it's hard to figure out. My fear is one day on a long trip out of state is when it won't snap out of it, and then I'll be stuck on a trip without my boat. I did have the dealer that put a seal kit in last year look into this problem and their answer was it ran well for them.... :blue:

 

[ondarvr]

Make sure the timing is advancing when you throttle up, pull the cowl off and and check. It may be sticking when it hasn't been used in a while.

 

[kofkorn]

I recently had a very similar issue with a 70 hp Johnson. It was only running on two cylinders until it warmed up. I would start it, and put it in gear at about 1/2 throttle. It would trudge along for about 5 min and then you could feel the last cylinder kick in every once in a while. Then all of a sudden, it would catch and run great the rest of the day. I could shut it down, come back 3hrs later and it still ran great. But go out the next morning and try it, and same thing would happen. I ran a few checks and determined that the trigger was ok, but the pack wasn't sending to the coil. I replaced the power pack and everything was fine.

Normally I agree that electronics usually go the other way, failing once warmed up, but in my case it was the opposite.

Good luck!

 

[scout-j-m]

I recently had a very similar issue with a 70 hp Johnson. It was only running on two cylinders until it warmed up. I would start it, and put it in gear at about 1/2 throttle. It would trudge along for about 5 min and then you could feel the last cylinder kick in every once in a while. Then all of a sudden, it would catch and run great the rest of the day. I could shut it down, come back 3hrs later and it still ran great. But go out the next morning and try it, and same thing would happen. I ran a few checks and determined that the trigger was ok, but the pack wasn't sending to the coil. I replaced the power pack and everything was fine.

Normally I agree that electronics usually go the other way, failing once warmed up, but in my case it was the opposite.

Good luck!

That's strange but good info. To the OP, a cylinder drop test will confirm if you have a similar issue. You can also use a timing light instead, although it may still work if you if fact have spark, but weak spark.

 

[dnyelator]

Still waiting for my lower unit oil from Amazon. When it gets here and I can fill up the lower unit, I'll run the above checks. I'm not sure sitting in the driveway without a load on that it will act up, but hopefully the drop test, spark test, moving wires around, one of those things will tell us something. Again, thank you all for the advice and helping an amateur like myself do some basic troubleshooting. This is an awesome forum!

 

[dnyelator]

Good morning folks, got my oil in the lower unit so I could finally run the cylinder drop test. The top two cylinders are firing fine, engine almost dies when I pull the plug wire. When I pull the wire on the bottom 2 cylinders the engine runs just the same, so it appears neither one is firing. So should I order up a power pack, or is there another test first? I forgot to wiggle the wires to see if it was a loose connection somewhere. Saw in kofkorn's post something about checking the "trigger", not sure what that is.

 

[ondarvr]

Did you check for spark, or just pull the wires off?

 

[jakedaawg]

Really should just do the basics first. Compression test, open air gap spark test, fuel sample. Those will tell you wether to chase mechanical, electrical, or carbs/fuel. If you start at the beggining it saves time in the end.

 

[dnyelator]

OK, so went out this afternoon to run the spark test and the fuel test (I don't have a compression gauge - yet). Just my luck, everything is running fine now. Just like my original post, I ran it yesterday afternoon for a while as I was troubleshooting, came back today to check spark, had good spark to all 4 cylinders, and when I did the load test, every cylinder dropped like it should, so there was no need to check the fuel since it's running good. Not sure what to do now, time here in NE to get it winterized, so I did that today. Might just have to buy the power pack and hope that's why it does this so intermittently. Looks like the pack is about $190. Is that something a backyard mechanic can do?