8hp Evinrude running poorly.

[dieselfuelonly]

Took carb apart cleaned it up, put it back together with all the original parts, fixed whatever was causing the idling issues. Think it might have been the new line that runs from the nozzle well to the idle orifice had a pinhole or something. Put the old one on idles fine now.

Ordered a OEM nozzle well. Will see what shows up and if it makes a difference. Curious to see what number it is and if there's any correlation to the idle restriction, and how it will compare to the other two I have.

 

[saltchuckmatt]

Took carb apart cleaned it up, put it back together with all the original parts, fixed whatever was causing the idling issues. Think it might have been the new line that runs from the nozzle well to the idle orifice had a pinhole or something. Put the old one on idles fine now.

Ordered a OEM nozzle well. Will see what shows up and if it makes a difference. Curious to see what number it is and if there's any correlation to the idle restriction, and how it will compare to the other two I have.

Fits 6, 8, 9.9 and 15.

Probably won't matter much.

 

[saltchuckmatt]

Fits 6, 8, 9.9 and 15.

Probably won't matter much.

Check that, I might have received the wrong info....fits 6 and 8. Same part number

 

[dieselfuelonly]

Check that, I might have received the wrong info....fits 6 and 8. Same part number

Makes sense, hopefully the two that I have are the wrong one and the one coming is right. No part numbers on either of the ones I have other than the "2" and "4" molded in the bottom.

I wonder what else in the carb, possibly incorrect parts, would explain fuel delivery issues making it run so rich.

 

[saltchuckmatt]

Check that, I might have received the wrong info....fits 6 and 8. Same part number

9.9 and 15 also. Just a plastic container. Next part?

 

[dieselfuelonly]

9.9 and 15 also. Just a plastic container. Next part?

Here's some video of it running on the lake. First part of the video the idle circuit was still working. The carb was using the nozzle well with #4 molded in the bottom, this was NOT the nozzle the carb on the motor came with, I got this one with the other carb I bought off eBay.

Second part of the video at around 1:10, something happened that plugged the idle circuit, or maybe the little idle circuit tube that connects to the nozzle well got a pinhole in it - either way, it was not working. The engine would not idle at all. But it ran fantastic, it was no longer running too rich.

Here's a picture of the size difference between the two. #4 on left #2 on right. I wonder if either of these is the right one for this motor? I'm trying to wrap my head around what else could be causing the carb to give the engine so much fuel and run so rich.

 

[dieselfuelonly]

What is strange about this whole thing is that from looking at the passages in the carb body, the top cover, etc., it leads me to believe that even if a well was used with too large of a idle passage, the idle fuel mixture delivered behind the throttle butterfly is 100% controlled by the idle mixture screw.

As I understand it the idle circuit is always in play on these carbs, and that's why there is only one mixture screw, but it has an effect throughout the entire RPM range. When shining a flashlight down the barrel of the carb running at above-idle RPM you can even see fuel coming through the idle circuit from behind the throttle butterfly, as well as getting sucked up through the emulsion tube in the venturi.

What else could cause the carb to be providing too much fuel? Something that could cause it to provide too much vacuum through the carb and pull too much fuel? I can't wrap my head around that at least.

I always tend to run the carb dry when I'm shutting down the engine, and I have noticed that the engine leans out and runs much better just as it's running out of fuel in the bowl. Could I have something crazy off in my setting of the float??? I've been doing it by the book as far as I know.

 

[dieselfuelonly]

Makes me wonder if maybe someone threw a different carb on there, like from a 9.9 or something. If that was the case, could it be fueling too much? The only number I have from the two carbs I have are the numbers stamped on the bodies of the carbs:

The one that came with the engine is MX338528, and the other used carb I bought is a MX340835. Not sure if that provides any useful information. Can't find much from looking up those numbers on google.

 

[saltchuckmatt]

Makes me wonder if maybe someone threw a different carb on there, like from a 9.9 or something. If that was the case, could it be fueling too much? The only number I have from the two carbs I have are the numbers stamped on the bodies of the carbs:

The one that came with the engine is MX338528, and the other used carb I bought is a MX340835. Not sure if that provides any useful information. Can't find much from looking up those numbers on google.

What about the whole piston skirt thing? Did you disprove that?

 

[dieselfuelonly]

What about the whole piston skirt thing? Did you disprove that?

I haven't torn the engine completely down to inspect, but here's what I was able to see through the exhaust ports and borescope through the ports to the cylinder walls.

 

[dieselfuelonly]

Almost positive this is an 8 hp carb...anyhow, it has a number 3 on it.

The OEM nozzle well arrived today, and you are right, it is supposed to be a #3.

The carb on this engine when I bought it had a #2 in it. The other eBay carb I bought had a #4.

#3 is what this carb is supposed to have. #2 appears to be the largest, and as the number molded on the bottom of the well goes up, the idle orifice size gets smaller. See pics at the end.

Is it possible this will resolve my issues? Maybe, though I doubt it. I would have thought the tiny #4 nozzle would have, but it didn't appear to have much effect. Mind you it plugged up immediately out on the lake and I no longer had much of an idle circuit LOL. Sure ran great after that, minus not idling though!

So the plan is:

Install #3 well in original carb. Test and see if I'm still 4-stroking at mid to high RPM. If that doesn't work, swap all good known carb parts over to the eBay carb. Re-test. If same behavior, I will pull the cylinder head and inspect the cylinder walls closer. If they show signs of skirt damage, will tear the engine completely down. Sound like a plan?

 

[saltchuckmatt]

The OEM nozzle well arrived today, and you are right, it is supposed to be a #3.

The carb on this engine when I bought it had a #2 in it. The other eBay carb I bought had a #4.

#3 is what this carb is supposed to have. #2 appears to be the largest, and as the number molded on the bottom of the well goes up, the idle orifice size gets smaller. See pics at the end.

Is it possible this will resolve my issues? Maybe, though I doubt it. I would have thought the tiny #4 nozzle would have, but it didn't appear to have much effect. Mind you it plugged up immediately out on the lake and I no longer had much of an idle circuit LOL. Sure ran great after that, minus not idling though!

So the plan is:

Install #3 well in original carb. Test and see if I'm still 4-stroking at mid to high RPM. If that doesn't work, swap all good known carb parts over to the eBay carb. Re-test. If same behavior, I will pull the cylinder head and inspect the cylinder walls closer. If they show signs of skirt damage, will tear the engine completely down. Sound like a plan?

Okay, post number 72 and rising!!!

Interesting. So the little hole on the right gets smaller on the larger number size, is that correct. To bad they don't list them that way.

Finicky little sob.

I don't think that's going to correct the mid range stuff but we shall see.

Still a dime a dozen around here.....

 

[dieselfuelonly]

Interesting. So the little hole on the right gets smaller on the larger number size, is that correct. To bad they don't list them that way.

Yep, larger number, smaller hole. I doubt its going to fix anything anyway, but I could see it letting too much fuel into the idle circuit with too large of a orifice, so we'll try and see what happens!

 

[ct1762@gmail.com]

Makes sense, hopefully the two that I have are the wrong one and the one coming is right. No part numbers on either of the ones I have other than the "2" and "4" molded in the bottom.

I wonder what else in the carb, possibly incorrect parts, would explain fuel delivery issues making it run so rich.

the 6hp carb has a MUCH smaller venturi/throat on the older style 6-8hp but look identical. just went through another 8hp for a customer yesterday and checked for you. are you 100% sure yours is an 8hp? do you have the part # on the block? very easy for a frisky previous owner to swap out the more common 6hp block if the original powerhead blew.

 

[dieselfuelonly]

the 6hp carb has a MUCH smaller venturi/throat on the older style 6-8hp but look identical. just went through another 8hp for a customer yesterday and checked for you. are you 100% sure yours is an 8hp? do you have the part # on the block? very easy for a frisky previous owner to swap out the more common 6hp block if the original powerhead blew.

I'm 99% sure it's an 8HP. The freeze plug on the block is stamped with E8RERE which from the serial decoder things I've found mean its a 1994 8HP. Looking at the paint on the engine where it meets the lower housing I didn't see any signs of the powerhead having been removed before.

I don't know of any other #s on the block, I can look though.

So I put the OEM nozzle well in the carb, no change. Tried using both the carb I got with the engine, and the one I bought off eBay, swapping the nozzle in between. No big changes between the two. Towards the end of my testing it was running like absolute garbage. Wouldn't idle at all, could barely keep it running at speed. I've probably fouled out the plugs.

Pulled the cylinder head off. Don't see any signs of damaged skirts, although I haven't split the crankcase and looked at the skirts themselves.. Felt the cylinder walls, there is absolutely nothing I can feel with my fingertips in terms of scoring. The scratching I do see on the walls seems pretty normal for the age of this engine and the crosshatching overall looks good. Nothing stuck out to me as a sign of worn skirts. Threw it in the garage and I've been using my little 4HP Yamaha instead, lol. It runs like a champ.

I'm stumped. I feel like it could very well still be a carb issue. When I pulled the head off, you could just see how much fuel was everywhere in the cylinders. Maybe I've got two garbage carbs.

Ya'll got any more ideas?? What else could cause the rich fuel mixture other than a bad carb?

Here's a video of what the cylinders look like.

 

[saltchuckmatt]

I'm 99% sure it's an 8HP. The freeze plug on the block is stamped with E8RERE which from the serial decoder things I've found mean its a 1994 8HP. Looking at the paint on the engine where it meets the lower housing I didn't see any signs of the powerhead having been removed before.

I don't know of any other #s on the block, I can look though.

So I put the OEM nozzle well in the carb, no change. Tried using both the carb I got with the engine, and the one I bought off eBay, swapping the nozzle in between. No big changes between the two. Towards the end of my testing it was running like absolute garbage. Wouldn't idle at all, could barely keep it running at speed. I've probably fouled out the plugs.

Pulled the cylinder head off. Don't see any signs of damaged skirts, although I haven't split the crankcase and looked at the skirts themselves.. Felt the cylinder walls, there is absolutely nothing I can feel with my fingertips in terms of scoring. The scratching I do see on the walls seems pretty normal for the age of this engine and the crosshatching overall looks good. Nothing stuck out to me as a sign of worn skirts. Threw it in the garage and I've been using my little 4HP Yamaha instead, lol. It runs like a champ.

I'm stumped. I feel like it could very well still be a carb issue. When I pulled the head off, you could just see how much fuel was everywhere in the cylinders. Maybe I've got two garbage carbs.

Ya'll got any more ideas?? What else could cause the rich fuel mixture other than a bad carb?

Here's a video of what the cylinders look like.

The 6 HP and the 8 hp have the same block so it wouldn't matter. They just let the motor spin up more with carberation and intake.

Are you using your 4 on the rubber boat? I still think all the barrell running and lugging it on the rubber boat has fouled it up. It's either that or you have the worst luck of all time.

 

[dieselfuelonly]

The 6 HP and the 8 hp have the same block so it wouldn't matter. They just let the motor spin up more with carberation and intake.

Are you using your 4 on the rubber boat? I still think all the barrell running and lugging it on the rubber boat has fouled it up. It's either that or you have the worst luck of all time.

Yeah I've been using the 4 horse on the inflatable, had it out today actually. That little Yamaha runs great, although it really struggles to get that boat up on plane, but usually I'm just out there to fish so I'm happy to putz along at 1/3 throttle anyway and take my time.

I don't know if you saw the video I posted above, but here is the Evinrude 8 on the same boat out on the lake from a few weeks ago. This was before I put the correct nozzle well in, this was with the well with the smallest orifice in it that I'm guessing is usually paired with the 6HP carb.

It 4 stroked like crazy until the idle circuit clogged up, then it would no longer idle, but it ran fantastic when wound up. Skip to about 1:15 in the video and you'll see it running when it's not getting so much fuel.

It all seems fuel/carb related. I'm just not sure what else could cause it besides the carb, and I can't justify taking a gamble on another unknown used carb only to end up right back here.

 

[ct1762@gmail.com]

The 6 HP and the 8 hp have the same block so it wouldn't matter. They just let the motor spin up more with carberation and intake.

Are you using your 4 on the rubber boat? I still think all the barrell running and lugging it on the rubber boat has fouled it up. It's either that or you have the worst luck of all time.

i fogot this is the newer block. 1990 and earlier had different intake/reeds and heads. The blocks on the old 8hp's are ported differently in both intake and exhaust as well if memory serves.
there are different part #'s for the 6's and 8's of this era, however. are you sure they are ported the same? the 8hp seems to have a TON more power than the 6's up top, of course easily explained by the larger carb.

 

[ct1762@gmail.com]

i fogot this is the newer block. 1990 and earlier had different intake/reeds and heads. The blocks on the old 8hp's are ported differently in both intake and exhaust as well if memory serves.
there are different part #'s for the 6's and 8's of this era, however. are you sure they are ported the same? the 8hp seems to have a TON more power than the 6's up top, of course easily explained by the larger carb.

 

[ct1762@gmail.com]

Yeah I've been using the 4 horse on the inflatable, had it out today actually. That little Yamaha runs great, although it really struggles to get that boat up on plane, but usually I'm just out there to fish so I'm happy to putz along at 1/3 throttle anyway and take my time.

I don't know if you saw the video I posted above, but here is the Evinrude 8 on the same boat out on the lake from a few weeks ago. This was before I put the correct nozzle well in, this was with the well with the smallest orifice in it that I'm guessing is usually paired with the 6HP carb.

It 4 stroked like crazy until the idle circuit clogged up, then it would no longer idle, but it ran fantastic when wound up. Skip to about 1:15 in the video and you'll see it running when it's not getting so much fuel.

It all seems fuel/carb related. I'm just not sure what else could cause it besides the carb, and I can't justify taking a gamble on another unknown used carb only to end up right back here.

sorry for the previous double-post. I do see you have an aftermarket double coil. in my experience, they are horrible. Ive had 4 just this season go bad in under an hour of running. it still might be ignition related. the sensor coil was tested? one easy thing to do to rule out ignition is get a set of coil extenders from stevens electronics or CDI. hook a dva meter up to it. voltage should be a steady 200-400v. if its dipping/breaking up, you know its probably the pack, ignition coil, or sensor coil. sometimes issues like that are as simple as a bad plug or plug wire as well. all easy to test and will show up with the coil extenders.