8hp Evinrude running poorly.

[dieselfuelonly]

1994 Evinrude 8hp E8RERE:

Still fighting this motor to get it running right.

It starts easy cold or warm, when cold it seems to like 1 pull on choke, one or two pulls no-choke and fires right up.

Once warm starts easy with no choke and some throttle.

I have a service manual for this exact year, so I've been through a lot of that. Here is what I've done so far:

- Disassembled the carb completely twice. Clean as a whistle. The three little tiny tiny holes on the top of the aluminum carb housing are 100% clean and clear. Plastic top cover seems to be in good shape. The upper and lower gaskets around the well were in bad shape so those have been replaced. All other gaskets are in good shape. I have adjusted the mixture screw to find the highest idle RPM after warming the engine up and backed off 1/8th of a turn. You can go from idle to full throttle and the engine doesn't backfire or surge which to me seems to indicate the mixture is set in a good spot.

- New plugs, gapped .030, with maybe a couple hours on them between testing in a drum and at the lake
- Followed the link & sync procedure to a tee and made all appropriate adjustments.
- Compression is good - 116 and 117 lbs, cold, after running the carb dry and engine sat overnight.
- Checked fuel pump screen, clean as can be
- No leaks from fuel lines, replaced fuel line quick connect as the one I got with the motor was leaking when squeezing the bulb to prime.
- Adjusted float level so it's level with the carb housing when the housing is upside down, and the bottom hangs 1 1/4" below the carb housing when measured holding the carb right-side up. Primes fine and stops letting fuel in when bowl is full.

To do the following electronic tests I've used a Fluke 88V in peak MIN/MAX mode to take the voltage readings. I'm not sure how this compares to the DVA Evinrude suggests using, but it takes a reading at 250 micro-seconds which from what I have read is perfectly acceptable for ignition voltage readings. My findings mirror the figures in the service manual so I'm inclined to believe it's accurate for these tests.


- Tested the stator voltage - 312v when cranking
- Tested the stator for shorts - no shorts when cranking, or when twisting the throttle handle
- Tested stator resistance - 950 ohms

- Tested sensor coil for shorts - no shorts when cranking, or when twisting the throttle handle
- Tested sensor coil voltage - can't remember what it read, but it was WAY above the 1.5 volt minimum. Want to say I got 20-30+ volts.
- Tested sensor coil resistance - 42 ohms

- Tested ignition coil primary resistance - 0.1 ohms on both 1 and 2
- Tested ignition coil secondary resistance - around 300 ohms both 1 and 2

- Tested spark plug wires - tested good near 0 ohms, checked while wiggling wires to make sure no shorts.

- There were some tests on the power pack that looked like they need some special equipment to do, so I took a chance and ordered a new CDI one. I hate throwing parts at a problem, but at least now I have a spare. No change.

- The one test I haven't done yet that I would like to do is testing the spark with a gap tester to make sure it can jump the 1/2" gap the service manual suggests. Not sure where I left my tester and haven't found it yet.

Issues I am having with the engine (see video below):

The engine seems to have a miss or be "4-stroking" a lot. Seems to idle well to my ear, but at mid/high RPMs in the test drum it does not seem to be running as smooth as it should. On the lake _IF_ it can get my small inflatable up on plane it runs well at higher RPM, but it struggles the whole time to get it up on plane and seems low on power due to the rough running. Mid-range RPM results in some rough running.

It's difficult to get the idle speed below around 850 RPM while in gear without stalling. It will do it, but going from a higher RPM back idle set below this point will generally cause the engine to stall unless the throttle is brought down VERY slowly.

I pulled the flywheel and checked out the stator and the sensor underneath, didn't see any issues with the wiring. The upper crankcase seal does seem to be weeping a bit, but I sprayed it with some soap and spun the motor over and no bubbles, so I can't see it being a major enough of a leak to cause this bad of running issues. Not sure how I'd go about testing the lower seal without pulling the whole powerhead.

At the bottom is a link to a video of the engine running in a drum.

I would really appreciate any further advice. Happy to do whatever testing I can with the tools I have available to provide further information, I'm a truck mechanic. I have a timing light although I am unsure how well it will work with the high RPM of the 2-stroke.

Thanks!!

 

[saltchuckmatt]

1994 Evinrude 8hp E8RERE:

Still fighting this motor to get it running right.

It starts easy cold or warm, when cold it seems to like 1 pull on choke, one or two pulls no-choke and fires right up.

Once warm starts easy with no choke and some throttle.

I have a service manual for this exact year, so I've been through a lot of that. Here is what I've done so far:

- Disassembled the carb completely twice. Clean as a whistle. The three little tiny tiny holes on the top of the aluminum carb housing are 100% clean and clear. Plastic top cover seems to be in good shape. The upper and lower gaskets around the well were in bad shape so those have been replaced. All other gaskets are in good shape. I have adjusted the mixture screw to find the highest idle RPM after warming the engine up and backed off 1/8th of a turn. You can go from idle to full throttle and the engine doesn't backfire or surge which to me seems to indicate the mixture is set in a good spot.

- New plugs, gapped .030, with maybe a couple hours on them between testing in a drum and at the lake
- Followed the link & sync procedure to a tee and made all appropriate adjustments.
- Compression is good - 116 and 117 lbs, cold, after running the carb dry and engine sat overnight.
- Checked fuel pump screen, clean as can be
- No leaks from fuel lines, replaced fuel line quick connect as the one I got with the motor was leaking when squeezing the bulb to prime.
- Adjusted float level so it's level with the carb housing when the housing is upside down, and the bottom hangs 1 1/4" below the carb housing when measured holding the carb right-side up. Primes fine and stops letting fuel in when bowl is full.

To do the following electronic tests I've used a Fluke 88V in peak MIN/MAX mode to take the voltage readings. I'm not sure how this compares to the DVA Evinrude suggests using, but it takes a reading at 250 micro-seconds which from what I have read is perfectly acceptable for ignition voltage readings. My findings mirror the figures in the service manual so I'm inclined to believe it's accurate for these tests.


- Tested the stator voltage - 312v when cranking
- Tested the stator for shorts - no shorts when cranking, or when twisting the throttle handle
- Tested stator resistance - 950 ohms

- Tested sensor coil for shorts - no shorts when cranking, or when twisting the throttle handle
- Tested sensor coil voltage - can't remember what it read, but it was WAY above the 1.5 volt minimum. Want to say I got 20-30+ volts.
- Tested sensor coil resistance - 42 ohms

- Tested ignition coil primary resistance - 0.1 ohms on both 1 and 2
- Tested ignition coil secondary resistance - around 300 ohms both 1 and 2

- Tested spark plug wires - tested good near 0 ohms, checked while wiggling wires to make sure no shorts.

- There were some tests on the power pack that looked like they need some special equipment to do, so I took a chance and ordered a new CDI one. I hate throwing parts at a problem, but at least now I have a spare. No change.

- The one test I haven't done yet that I would like to do is testing the spark with a gap tester to make sure it can jump the 1/2" gap the service manual suggests. Not sure where I left my tester and haven't found it yet.

Issues I am having with the engine (see video below):

The engine seems to have a miss or be "4-stroking" a lot. Seems to idle well to my ear, but at mid/high RPMs in the test drum it does not seem to be running as smooth as it should. On the lake _IF_ it can get my small inflatable up on plane it runs well at higher RPM, but it struggles the whole time to get it up on plane and seems low on power due to the rough running. Mid-range RPM results in some rough running.

It's difficult to get the idle speed below around 850 RPM while in gear without stalling. It will do it, but going from a higher RPM back idle set below this point will generally cause the engine to stall unless the throttle is brought down VERY slowly.

I pulled the flywheel and checked out the stator and the sensor underneath, didn't see any issues with the wiring. The upper crankcase seal does seem to be weeping a bit, but I sprayed it with some soap and spun the motor over and no bubbles, so I can't see it being a major enough of a leak to cause this bad of running issues. Not sure how I'd go about testing the lower seal without pulling the whole powerhead.

At the bottom is a link to a video of the engine running in a drum.

I would really appreciate any further advice. Happy to do whatever testing I can with the tools I have available to provide further information, I'm a truck mechanic. I have a timing light although I am unsure how well it will work with the high RPM of the 2-stroke.

Thanks!!

Have you tested it on a boat? Your revving it way to high in that barrel.

 

[dieselfuelonly]

Have you tested it on a boat? Your revving it way to high in that barrel.

Yeah had it out on the water. Same rough running, seems to idle OK and if it can get up on plane, smooths out at high RPM. But anywhere in between is rough.

 

[saltchuckmatt]

Yeah had it out on the water. Same rough running, seems to idle OK and if it can get up on plane, smooths out at high RPM. But anywhere in between is rough.

I have a 92 that I bought in 92 brand new and it purrs like a kitten. I'm not sure about your meter but my ear says you idling about right. Pretty sure your bogging that thing down to much when you crank it up in the barrel...not made to do that. Big test tank maybe.

The inflatable? Is it a hard bottom? Some inflatables have quite a bit of resistance and you look like a big guy so not sure there. I have a 12 alum boat and it kicks right along but I have to move way forward to get it up on a plane and wind it up.

You've done a lot that's for sure....any compression numbers?

 

[saltchuckmatt]

I have a 92 that I bought in 92 brand new and it purrs like a kitten. I'm not sure about your meter but my ear says you idling about right. Pretty sure your bogging that thing down to much when you crank it up in the barrel...not made to do that. Big test tank maybe.

The inflatable? Is it a hard bottom? Some inflatables have quite a bit of resistance and you look like a big guy so not sure there. I have a 12 alum boat and it kicks right along but I have to move way forward to get it up on a plane and wind it up.

You've done a lot that's for sure....any compression numbers?

I see your compression numbers so skip that. They look good.

 

[dieselfuelonly]

I have a 92 that I bought in 92 brand new and it purrs like a kitten. I'm not sure about your meter but my ear says you idling about right. Pretty sure your bogging that thing down to much when you crank it up in the barrel...not made to do that. Big test tank maybe.

The inflatable? Is it a hard bottom? Some inflatables have quite a bit of resistance and you look like a big guy so not sure there. I have a 12 alum boat and it kicks right along but I have to move way forward to get it up on a plane and wind it up.

You've done a lot that's for sure....any compression numbers?

Yeah I realize the barrel is not ideal for testing. Unfortunately the lake isn't close by, and the engine acts up in the mid-higher RPM ranges, and the barrel isn't exactly good for that. Even though its bogging, I feel like it shouldn't start missing/4-stroking? I'll link a video of it running at the lake at the end of this post. This was before I did the link & sync procedure and some more work on the carb.

The inflatable is a SIB, has an inflatable keel. 8' 6". I'm not really a big guy, probably around 160-170 or so. I've watched a few videos of other 8's and they seem to be running so much smoother than mine through the midrange.

Here's a video of this engine, and below it is a video of someone else's that seems to be running much better. I realize comparing the inflatable to an aluminum flat bottom is apples to oranges, but listening to how his engine runs compared to mine I know mine isn't running right.

I've got a DVA adapter coming so I can make 100% sure the readings from my Fluke meter are accurate - like I said I'm not sure how the peak readings the Fluke takes compare to an actual DVA.

The only ignition component that tests weird right now is the sensor. If I take a peak reading it produces around 15-20 volts, if I take a normal reading like you would with any other voltmeter I see about 0.5 volts. Spec in the manual seems to be a minimum of 1.5 volts with around 3 volts being average. Resistance on it is perfectly in spec. I'm not sure if I'm not getting this weird voltage reading because of the lack of a DVA, or because the sensor is bad. Got a new sensor on the way along with the DVA just in case it tests bad.

This engine on my inflatable -

Someone else's 8hp Evinrude for comparison -

 

[909]

I'd first start with your boat. Small inflatables are incredibly hard to plane.

Shift all your weight to the front as much as possible and move your gas tank there as well. Stretch your arm back to the tiller as far as you can reach.... while sitting as far forward as you possibly can.

Make sure your tubes and keel are inflated to 3psi at the very minimum. Especially your keel. The tubes and keel should be hard enough to stand on. You need structural rigidity , otherwise you lose performance, making it difficult to plane in your videos. You might want to try to raise the pin a notch. Or try and use shim to raise your outboard (experiment with different thicknesses) . Swap your prop to a lower pitch, it should not take that long to plane on an inflatable that essentially floats on the surface.

 

[dieselfuelonly]

Thanks for the reply, from what you saw/heard in the video do you think the engine seems to be running well, especially while under mid-range rpm? I unfortunately don't have much experience with 2-strokes to have a good ear for how one should run. It feels rough to me at times, but maybe that's just me.

 

[saltchuckmatt]

Yeah I realize the barrel is not ideal for testing. Unfortunately the lake isn't close by, and the engine acts up in the mid-higher RPM ranges, and the barrel isn't exactly good for that. Even though its bogging, I feel like it shouldn't start missing/4-stroking? I'll link a video of it running at the lake at the end of this post. This was before I did the link & sync procedure and some more work on the carb.

The inflatable is a SIB, has an inflatable keel. 8' 6". I'm not really a big guy, probably around 160-170 or so. I've watched a few videos of other 8's and they seem to be running so much smoother than mine through the midrange.

Here's a video of this engine, and below it is a video of someone else's that seems to be running much better. I realize comparing the inflatable to an aluminum flat bottom is apples to oranges, but listening to how his engine runs compared to mine I know mine isn't running right.

I've got a DVA adapter coming so I can make 100% sure the readings from my Fluke meter are accurate - like I said I'm not sure how the peak readings the Fluke takes compare to an actual DVA.

The only ignition component that tests weird right now is the sensor. If I take a peak reading it produces around 15-20 volts, if I take a normal reading like you would with any other voltmeter I see about 0.5 volts. Spec in the manual seems to be a minimum of 1.5 volts with around 3 volts being average. Resistance on it is perfectly in spec. I'm not sure if I'm not getting this weird voltage reading because of the lack of a DVA, or because the sensor is bad. Got a new sensor on the way along with the DVA just in case it tests bad.

This engine on my inflatable -

Someone else's 8hp Evinrude for comparison -

Boat is an issue but your right, might be something in the mid-range power. Or maybe not.

As far as it shutting down coming down from higher R's? I believe that is because it's bogging down and not recuperating before you bring it to a slow idle. When I bomb around with mine, I slow down in intervals before going to a slow troll.

 

[909]

Run the engine in gear at full throttle for one minute

Quickly reduce the speed to slow ( 700 -800 rpm ) + shift to neutral

The engine should continue to run smoothly

If the engine stalls or backfires , the idle mixture is too lean

 

[dieselfuelonly]

Run the engine in gear at full throttle for one minute

Quickly reduce the speed to slow ( 700 -800 rpm ) + shift to neutral

The engine should continue to run smoothly

If the engine stalls or backfires , the idle mixture is too lean

I saw that procedure in the service manual for the below 5HP models. For the 5-8HP models, this was the "test".

8. Start the engine and allow it to reach normal operating
temperature. Shift the motor into forward gear. Rapidly advance
throttle to wide open position. If the engine stalls or backfires, the
idle mixture is too lean. Turn the low-speed needle Va of a turn
counterclockwise. If necessary, repeat this procedure.

Wonder why the difference.

For what its worth, my engine doesn't backfire or stall or anything of the sort when doing the above test. However, going from high speed > low idle, especially with an idle set at around 700 RPM, it will stall. Its possible the DMM is reading the idle speed wrong and it's lower than it's actually reporting, but my engine seems to idle happy around 850 or so, below that and it will tend to stall coming down quickly from high throttle.

 

[ct1762@gmail.com]

this reeks of shot piston skirts to me. compression has nothing to do with it. Hope i'm wrong, but the issue with not being able to idle below 950rpm is a dead giveaway. these things should idle down in neutral a few hundered rpm lower than that without stalling. did you try squirting mixed fuel into the carb with a precise syringe when it wants to stall? its frustrating I know but when everything tests fine and all fuel systems are clean and it still wont run i'd put a borescope down the holes and take a peek.

 

[dieselfuelonly]

this reeks of shot piston skirts to me. compression has nothing to do with it. Hope i'm wrong, but the issue with not being able to idle below 950rpm is a dead giveaway. these things should idle down in neutral a few hundered rpm lower than that without stalling. did you try squirting mixed fuel into the carb with a precise syringe when it wants to stall? its frustrating I know but when everything tests fine and all fuel systems are clean and it still wont run i'd put a borescope down the holes and take a peek.

Interesting, I can put a scope down there and take a look. I'm not very familiar with these 2-strokes, especially on an outboard - I take it I can see the skirts through the exhaust ports? What covers, etc., need to come off to gain access? Haven't looked through the powerhead section of the service manual so sorry if my questions are answered there. I'm curious as to what effect the worn piston skirts have on a 2-stroke in terms of its running operation? Are there other symptoms besides not wanting to idle?

And lets say this thing does end up needing a rebuild, and assuming the block and crank are good, is it gonna be relatively easy to source new parts for this thing, or do I just cut my losses?

And to answer your question, I haven't tried squirting some fuel in. It will idle down to 700ish RPM, but it doesn't like to go from a running RPM down to that range without stalling. I have to take it down that low very slowly. The other possible issue is maybe my Fluke meter with the inductive pickup just doesn't read this thing accurately and the RPM is lower than I'm thinking it is when I'm trying to set it around 700. I haven't checked it against anything else. I will check it with a photo tach and see if I'm getting a similar reading.

 

[ct1762@gmail.com]

symptoms would be hard to start when warm, poor idle, rough idle, maybe an occasional pop, but will seem to run ok at higher rpms. Again hopefully not the case. You should be able to just look down the cylinders at the exhaust side especially to see any scoring. the exhaust cover would be better as you can see the skirts, or tiny parts of them. If you get the stevens load adapter, you can test the pack, and coil extenders to rule out ignition coil/pack. parts are pretty easy to find. i will say those plastic top carbs can cause issues so make sure its torqued in sequence on the plate, and its not worn where the needle sits. you said it has a primer system... all of these newer style 1991-up 6/8hp have a choke system as the primer caused issues. I've actually used older 6hp/7.5/8hp carbs on these and ran great, as the plastic tops are impossible to find for a sane price. note: there was a factory bulletin/upgraded plastic top for these i believe as the old ones had some issues. would be interesting to see if an old all-metal carb makes it behave properly. they are a dime a dozen, but youd need to make a choke linkage for it to work, and possible enlarge the main jet depending on what carb you got. i have a 1994 8hp with the old carb. can send pics.

 

[dieselfuelonly]

symptoms would be hard to start when warm, poor idle, rough idle, maybe an occasional pop, but will seem to run ok at higher rpms. Again hopefully not the case. You should be able to just look down the cylinders at the exhaust side especially to see any scoring. the exhaust cover would be better as you can see the skirts, or tiny parts of them. If you get the stevens load adapter, you can test the pack, and coil extenders to rule out ignition coil/pack. parts are pretty easy to find. i will say those plastic top carbs can cause issues so make sure its torqued in sequence on the plate, and its not worn where the needle sits. you said it has a primer system... all of these newer style 1991-up 6/8hp have a choke system as the primer caused issues. I've actually used older 6hp/7.5/8hp carbs on these and ran great, as the plastic tops are impossible to find for a sane price. note: there was a factory bulletin/upgraded plastic top for these i believe as the old ones had some issues. would be interesting to see if an old all-metal carb makes it behave properly. they are a dime a dozen, but youd need to make a choke linkage for it to work, and possible enlarge the main jet depending on what carb you got. i have a 1994 8hp with the old carb. can send pics.

Gotcha. I'll try to get another video of how its behaving. It does start great when warm. Is the exhaust cover under the plate that has the weep hose for the water pump attached?

Will try to get some verification of the actual idle speed I'm running at. I am guessing i can test the coil packs output under load, at least the test in the manual that mentioned seeing at least 200v at the primaries. Figure I can shove a wire up there, but the boot on, then hook the meter up to that.

 

[ct1762@gmail.com]

if you see 200v at the primaries with a coil extender, there is nothing wrong with the ignition. if a coil was shot, 9/10 youd hear it zapping to ground. exhaust cover is not underneath powerhead. port side where the indicator hose enters the block. that thing with a bunch of screws is what you want to remove.

 

[saltchuckmatt]

if you see 200v at the primaries with a coil extender, there is nothing wrong with the ignition. if a coil was shot, 9/10 youd hear it zapping to ground. exhaust cover is not underneath powerhead. port side where the indicator hose enters the block. that thing with a bunch of screws is what you want to remove.

Careful with those bolts, they like to break off. Also, there is two parts under there so you will need two gaskets.

 

[dieselfuelonly]

if you see 200v at the primaries with a coil extender, there is nothing wrong with the ignition. if a coil was shot, 9/10 youd hear it zapping to ground. exhaust cover is not underneath powerhead. port side where the indicator hose enters the block. that thing with a bunch of screws is what you want to remove.

Dumb question, I disconnected the plug wire on one cylinder when I was doing some testing. Forgot to ground the plug wire out. I could hear the zap coming from the coil while it was running. Shut it off as soon as I heard it and realized I forgot to ground it. The running issue has been going on since before this occured, but a. is it normal to hear this zap from the coil if the charge has nowhere to go?, and b. could I have damaged the coil when I let it run like this for a few seconds? Like I said, the running issue has existed before I did that, but I'm wondering if the zap could be a sign of a coil issue. With everything connected up and the motor running "normally", I don't hear the zap any more.

 

[ct1762@gmail.com]

Dumb question, I disconnected the plug wire on one cylinder when I was doing some testing. Forgot to ground the plug wire out. I could hear the zap coming from the coil while it was running. Shut it off as soon as I heard it and realized I forgot to ground it. The running issue has been going on since before this occured, but a. is it normal to hear this zap from the coil if the charge has nowhere to go?, and b. could I have damaged the coil when I let it run like this for a few seconds? Like I said, the running issue has existed before I did that, but I'm wondering if the zap could be a sign of a coil issue. With everything connected up and the motor running "normally", I don't hear the zap any more.

no if the plug wire was allowed to arc, it shouldnt damage the coil. Especially if its not doing that when running its fine im sure.

 

[dieselfuelonly]

no if the plug wire was allowed to arc, it shouldnt damage the coil. Especially if its not doing that when running its fine im sure.

I don't think it was arcing out the plug wire. I had it pulled out away where I was planning to hook a lead to it to ground it out, but forgot. I heard it arcing from somewhere, but I'm not sure where it was arcing to. Curious if it's normal to hear the coil discharge to something when it isn't grounded out through the plug wire, or that could indicate a possible issue with the coil. But yeah when its running now back together, I don't hear anything abnormal from the coil.

UPS says the DVA adapter arrived. I'll redo all my ignition tests with that to make sure they sync up with what I was getting with just the meter.