Idle quality and general performance

[fl.graderman]

I bought my motor from a guy in Kentucky back in December and overall it runs pretty decent, (in my opinion), but I do have a couple "issues" that I've been trying to correct and need a little insight.
First, it's a 1996 Evinrude 25hp 3 cylinder 2 stroke. Model number is E25RMLEDC.
Since I bought it I have replaced the impeller, fuel filter, spark plugs and prop. I also added a marine tiny tach, (so I could accurately upgrade the prop).
The two main issues I have are one, it seems to idle rough. It shakes around pretty good at anything less than about 1300 rpms. I don't know if it has a miss or if this is normal for this motor.
And two, I've got, (what seems like), a lot of oil passing through the exhaust unburnt.
When I changed the plugs, I noticed some carbon on the top of the top piston, so today I dumped a can of seafoam in with about 3 gallons of gas and let it idle at about 1500 rpms for about 30 minutes thinking it would break down the carbon. While I was doing this, I took the induction wire from the tiny tach and switched from plug wire to plug wire trying to determine if all three were firing consistently. This is where it gets weird...
On the top wire, the tach seems to read properly at about 1500. On either of the other two, it was showing 2800 to 3200 rpms. I have the tach set for 360°. Is it possible that the engine was running at the higher rpm and the top cylinder is only firing 50% of the time and that is why I have so much unburnt oil coming through the exhaust?
Also FWIW, at WOT, it's showing me 5700-5800 on the top wire which is about where I need to be.
Here is a link to a short video of it idling to show how much it shakes and the oil blowing by...
https://youtu.be/ap76y2n7m_M

Any thoughts, opinions, advise are appreciated.

Edit to add...I should note that even though I disconnect the fuel line and run the gas out after every trip, it never takes more than two pulls to start and it has never stalled on me at any time.

2015 Tracker Grizzly 1448 MVX
1996 Evinrude 25hp 3 cylinder looper

 

[JMichael]

I'll wait for the professionals to answer your questions, but I wanted to ask if it clunks very hard when you put it in gear (fwd or rev). I was also wondering if those multi carb engines had vacuum ports for each carb so a sync tool could be connected.

 

[fl.graderman]

It goes into gear firm and smooth, no clunking. I'm not sure how a sync tool works, but I read the procedure in the service manual and it's synchronized mechanically. No mention of any special tool.

2015 Tracker Grizzly 1448 MVX
1996 Evinrude 25hp 3 cylinder looper

 

[JMichael]

Yes, the sync would be accomplished mechanically via the throttle linkage but the sync tool is attached via vacuum ports. I have to sync my 4 cyl 4 carb vintage motorcycle because the vast majority of the time none of the standard motorcycle shops will work on one over 10 years old. There are several styles of carb sync tools out there but the type used really doesn't mater that much. With all the johnnyrude guys on the forum, I would have expected one of them to jump in here by now. BTW, synchronizing the carbs is very critical to the smooth running and overall performance of a multi carb engine. It makes all the cylinders work/pull evenly, instead of one cylinder pulling most of the load and being overworked and getting hot as well as poor fuel mileage.

 

[JL8Jeff]

I had a 99 Johnson 40 hp that needed the idle air screws adjusted to get rid of the stutter/shaking. This seems to be the most common adjustment for outboards, both my Mercurys needed adjustment as well. Not sure about your tach reading, does the engine have multiple coils (one for each cylinder) that could be swapped around to see if the problem moves with it?

 

[fl.graderman]

I had a 99 Johnson 40 hp that needed the idle air screws adjusted to get rid of the stutter/shaking. This seems to be the most common adjustment for outboards, both my Mercurys needed adjustment as well. Not sure about your tach reading, does the engine have multiple coils (one for each cylinder) that could be swapped around to see if the problem moves with it?

Yes it has three coils, one per cylinder, and the top one has a much lower reading than the other two. I believe the top one is correct because when it says 1500 rpms, the motor sounds like it's at about 1500...not 2800 to 3200 like the other two claim. Plus WOT puts me between 5700 and 5800 where the manual says its supposed to be. I'm less concerned about the crazy tach readings than I am about the fuel/oil blowby.
The idle air screws are covered in a white silicone - type stuff as though someone had it tuned up and didn't want the screws messed with.

Edit to add picture

Is it normal for 2 strokes to lose this much unburnt fuel through the exhaust? I may be just over analyzing things because when she pops up on plane and takes off, it's hard to imagine it could have a serious problem...

Plus I was just reading that a characteristic of looper motors is a rougher idle.

2015 Tracker Grizzly 1448 MVX
1996 Evinrude 25hp 3 cylinder looper

 

[JL8Jeff]

I wonder if one of the floats is set too high allowing excess fuel/oil. I assume you're running pre-mix, what ratio are you using? My 94 Mercury 60/45 had the oil injection pump go bad so I pre-mix synthetic at 80:1 and still get an initial puff of smoke when starting it. I think one of my carb floats is off, but it runs pretty good so I really don't want to make it worse. If you're running regular 2 stroke at 50:1, you could try switching to synthetic and run 80 or 100:1 which should reduce the smoke a bit. I've run synthetic in several motors now and haven't had any issues, but I usually don't run around at WOT either.

 

[fl.graderman]

I wonder if one of the floats is set too high allowing excess fuel/oil. I assume you're running pre-mix, what ratio are you using? My 94 Mercury 60/45 had the oil injection pump go bad so I pre-mix synthetic at 80:1 and still get an initial puff of smoke when starting it. I think one of my carb floats is off, but it runs pretty good so I really don't want to make it worse. If you're running regular 2 stroke at 50:1, you could try switching to synthetic and run 80 or 100:1 which should reduce the smoke a bit. I've run synthetic in several motors now and haven't had any issues, but I usually don't run around at WOT either.

I am running Evinrude synthetic, however, I'm still mixing it 50:1. I wasn't aware you could reduce the amount of oil by switching to synthetic. Also it doesn't always smoke like it was in the video...when I recorded that video I was running seafoam through it. That was causing most of the smoke.

On a side note, I was reading about stuck rings. I did see carbon buildup on top of one of my pistons when I changed spark plugs. What are your thoughts on removing the plugs with the engine tilted up and pouring seafoam in the cylinders and letting it soak for a day or two. I would of course tilt it back down and pull the rope a couple times without the plugs in to clear it out before I started it. Do you think this would sufficiently clean the Pistons and free up any rings that might be sticking?

I would like to eliminate any of the simple stuff before I start messing with idle mixture screws and float levels and such...

2015 Tracker Grizzly 1448 MVX
1996 Evinrude 25hp 3 cylinder looper

 

[JL8Jeff]

It will take running time to clean out the carbon but you won't get rid of all of it. You need run time at higher engine speeds to truly burn off deposits so give it a couple of tanks of gas and then see what it looks like. I wouldn't pour any excessive fluids into the cylinders. You could pull the plugs and spray some seafoam into each cylinder and let it sit for a couple of days to help break down the carbon, but I would just run it first.

 

[perchjerker]

thats really weird someone would put silicone on the mixture screws. Makes me think someone has been messing with those carbs that doesnt know what they are doing. Can you tell if they have springs on them?

I have a '94 200 hp on my Grady White, its a big pig and idles like that. Yours looks like it but cut in half lol

Do that motor have VRO on it?

Mine does, they can cause issues but mine works fine

what do your spark plugs look like? I missed that if you already mentioned it

 

[fl.graderman]

thats really weird someone would put silicone on the mixture screws. Makes me think someone has been messing with those carbs that doesnt know what they are doing. Can you tell if they have springs on them?

I have a '94 200 hp on my Grady White, its a big pig and idles like that. Yours looks like it but cut in half lol

Do that motor have VRO on it?

Mine does, they can cause issues but mine works fine

what do your spark plugs look like? I missed that if you already mentioned it

Yes I can see the springs around the screw threads.

The plugs that were in it when I got it were dark brown to black and wet plus they were autolite plugs. I changed them to the recommended champion QL86C plugs and noticed an instant improvement in performance but I haven't checked them again for fouling..

No there is no VRO on it. Obviously removed by PO. I would have done the same however after what I've read about them.
2015 Tracker Grizzly 1448 MVX
1996 Evinrude 25hp 3 cylinder looper

 

[perchjerker]

The no VRO could be part of the problem. You may have to play with the fuel/oil ratio. I also use XD100 (I get it in bulk from the dealer and its not that expensive that way) might be overkill but its very clean burning

The motor is designed for the VRO, that might be why its not liking idling. You say its running fine off idle? Syncing and timing the engine properly is also real important (at least on my V6 it is)

This is just a guess, this is the only VRO motor I have ever had

You may want to go over the The Continuous Wave (boston whaler forum) and ask about it. There are a few guys on there who really know these motors, plus you may be able to find something in their tech files.

 

[richg99]

Great recommendation on Continous Wave. Those Boston Whalers guys have been around for a long time and do know their stuff. Lots of times, when I Google something, up comes a C.W. thread with the answer. richg99

 

[NautiBuoys]

You may want to get a copy of that engine's Service manual on Ebay. They're relatively cheap and tell you how to set up the carbs, linkages, etc, etc.

You may also want to do a search on Pappy; per his bio he spent 4 years in OMC (Johnson /Evinrude) Engineering and 22 more as a Johnson/Evinrude Factory Tech Rep in Florida. He owns 3 or 4 of those 3 cylinder 25/35 outboards and has said on this site its one of the best ever built, save that constant (50:1) oil mixer unit (it is not a VRO). Best thing that other guy ever did was to pull that out. Pappy may have previously stated some ideas and if not, may jump in to help you.

They are known to be one of the smoothest, quietest idling 2 stroke engines ever built. I have a 1998 35hp (pulled the oil mixer as Pappy suggested), and to which I can attest to how smooth and quiet it is.

 

[fl.graderman]

You don't have to lurk around this site too long to hear about Pappy and figure out he's an evinrude guru. I was actually hoping he would see this thread. I didn't know he was a fellow florida boy though. I'll start sifting some his posts tonight and see what I can find that may pertain to my motor. Thanks for the suggestion. Great idea!

2015 Tracker Grizzly 1448 MVX
1996 Evinrude 25hp 3 cylinder looper