8hp Evinrude running poorly.

[oldboat1]

Carb kits include two or three gaskets for different models. Pick the one that fits your configuration -- possible to block openings with an incorrect gasket. Also, the fuel pump gasket should be supple. If it is stiff and holds a set, it needs to be replaced.

 

[dieselfuelonly]

the exhaust is a wet water-cooled exhaust so it will look milky when freshly mixed with water. if it wasn't cooled by a "wall of water" it would get so hot paint would melt off the midsection. while your in there id replace the gaskets... which is sort of more of a pain on those as it has an adapter plate. doesnt seem bad to me though. i still think your issue is the carb. 6 turns out seems quite rich. what does the manual say? i believe its around 4 turns. you arent gonna get a bad lean sneeze from plastic topped motors generally the needles are more sluggish. run it full throttle for a couple minutes then quickly back off till you get it to sneeze, then richen (counterclockwise) until it just stops sneezing, then back off 1/8 to prevent a lean idle in neutral. id try one of the older carbs as i mentioned.

I'm back at it again after getting the powerhead seal kit.

I removed the old lower crank seal and installed the new one. I also installed the new gaskets for the side covers over the exhaust ports. I didn't replace any of the other gaskets as they were in decent enough shape to throw back on there and see if it runs any better. I know I should replace that exhaust housing gasket, which I will do if I ever get this thing figured out.

Put the carb back on, in the drum it goes, got it running and... seems to run exactly the same - like garbage. I gave up and that was it for last night.

Today, the carb I ordered from eBay came in. There were a couple differences (on the top of the aluminum housing there were 2 tiny holes instead of 3, for example), but other than that it seemed nearly identical to my carb. It needed a good cleaning and I threw it on the motor after swapping a few missing linkages and the bowl from the original carb (this carb appears to have a drain in the bowl which is missing a plug).

On this new carb, the mixture screw is much closer to the "3 turns out" position than on my old carb when I got it idling happy.

And again, the motor still runs like garbage in the midrange and struggles to get into the higher end.

It was getting dark and I was shining my flashlight into the mouth of the carb just watching. I swear in the right light I could see fuel reflecting off the flashlight that wasn't getting sucked out the top of the emulsion tube. It more appeared to be coming out from below the top of the tube, kind of where it goes into the aluminum base of the carb.

Is it possible that on BOTH these carbs I have now, the tube is not sealing to the body of the carb and sucking fuel past?

Would this explain the poor midrange and 4-stroking, as apparently NOTHING else I do will?

I watched in the carb at idle. No fuel coming up through the tube, so running completely off the idle circuit I'm assuming.

At mid throttle, fuel would start coming out the tube (as well as I believe from around the tube) and the engine would bog and bit and generally seem like it was running really rich. If I cranked the throttle wide open for a brief second it would smooth out some once it got some more RPM built up, but I can't really let it go full bore inside my drum.

As I try to wrap my head around yet another failure to find out why this thing won't run right, I wonder if that could be it. At idle, its running off the idle circuit not pulling fuel. Wide open, it can burn almost all the fuel its sucking out of the tube and from around it, and runs okay-ish. At mid range, the vacuum is strong enough to pull fuel from both through and around the tube which makes the engine run extremely rich. Of course, this would mean I also have managed to get two carbs with exactly the same problem. Which is definitely probable considering the cursed nature of this motor.

So that begs my next question - how do I attempt to seal off the tube and see if that makes a difference?

 

[dieselfuelonly]

I apparently missed this in one of your posts ct1762 -

but you can just put some thread locker around the base to rule it out.

Will the threadlocker hold up against the fuel, or is this just a temp fix to test? Also, any particular, blue, red?

 

[saltchuckmatt]

I apparently missed this in one of your posts ct1762 -



Will the threadlocker hold up against the fuel, or is this just a temp fix to test? Also, any particular, blue, red?

First of all, I think you should change the posting name to "How can I fix this motor for twice as much as getting a new one!"

I'll tell you, I thought I was bad but sheesh.

Gotta tell you though I'm giving you straight A's for persistence!

Ok, straight from the omc book testing for leaks at the emulsion tube and carb body.

Invert carb body and fill idle circuit with isopropyl alcohol.

Check for leaks.

If leaks occur, blow dry and apply a drop of omc ultra lock at point of connection.

 

[saltchuckmatt]

I apparently missed this in one of your posts ct1762 -



Will the threadlocker hold up against the fuel, or is this just a temp fix to test? Also, any particular, blue, red?

 

[dieselfuelonly]

First of all, I think you should change the posting name to "How can I fix this motor for twice as much as getting a new one!"

I'll tell you, I thought I was bad but sheesh.

Gotta tell you though I'm giving you straight A's for persistence!

LOL well other than a lot of my time I can't say I've spent a bunch of money on this thing for unnecessary parts, though jury is still out on whether the eBay carb was worth it or if its just as junk as the first one. If nothing else got the plastic cover from it which is in great shape.

Definitely needed the ignition coil with weak spark on one cylinder, sensor voltage was way out of spec but who knows if there was actually anything wrong with it. Idles better with the new one? Needed the powerhead gasket kit after removing the exhaust covers to inspect the skirts and cylinders, and that came with the crank seals too which the upper definitely needs to be replaced, can't say for sure about the lower, but it's on there anyway.

The price of my sanity though... how much is that worth? Don't know if I'll ever be able to afford getting that back after this thing. Will loctite the carb and report back??!

 

[saltchuckmatt]

LOL well other than a lot of my time I can't say I've spent a bunch of money on this thing for unnecessary parts, though jury is still out on whether the eBay carb was worth it or if its just as junk as the first one. If nothing else got the plastic cover from it which is in great shape.

Definitely needed the ignition coil with weak spark on one cylinder, sensor voltage was way out of spec but who knows if there was actually anything wrong with it. Idles better with the new one? Needed the powerhead gasket kit after removing the exhaust covers to inspect the skirts and cylinders, and that came with the crank seals too which the upper definitely needs to be replaced, can't say for sure about the lower, but it's on there anyway.

The price of my sanity though... how much is that worth? Don't know if I'll ever be able to afford getting that back after this thing. Will loctite the carb and report back??!

Where I'm from there is 2 to 3 a week for sale on Craigs....

But what fun is that!

 

[dieselfuelonly]

Where I'm from there is 2 to 3 a week for sale on Craigs....

But what fun is that!

Wish the market here was that good! I'd have just bought another lol

 

[dieselfuelonly]

the exhaust is a wet water-cooled exhaust so it will look milky when freshly mixed with water. if it wasn't cooled by a "wall of water" it would get so hot paint would melt off the midsection. while your in there id replace the gaskets... which is sort of more of a pain on those as it has an adapter plate. doesnt seem bad to me though. i still think your issue is the carb. 6 turns out seems quite rich. what does the manual say? i believe its around 4 turns. you arent gonna get a bad lean sneeze from plastic topped motors generally the needles are more sluggish. run it full throttle for a couple minutes then quickly back off till you get it to sneeze, then richen (counterclockwise) until it just stops sneezing, then back off 1/8 to prevent a lean idle in neutral. id try one of the older carbs as i mentioned.

After what I've seen today I'm now with you 100% that the issue lies with the carb.

See if you can explain this to me:

Rebuild the carb with the good Sierra gasket kit that took 2 weeks to get here. New needle and seat, set float height, replaced all gaskets, new rubber tube to idle circuit from the fuel well. Cleaned and blew air and carb cleaner through everything while I was in there. Used the plastic top cover from the used carb I bought as when idling the idle screw seemed to be in a much more "normal" position of around 2 1/2-3 turns out at just a hair richer than max idle speed. Red loctite around top (and bottom) of emulsion tube. Made sure little air intake screen and tube that inlets right at the bottom side of the emulsion tube is clear. Put my finger over top of the emulsion tube and over the screen and blew down around the tube. Can't make any air escape around it, pretty confident its sealed.

Engine idles good. Still runs like crap midrange, 4 strokes, smokes a lot, running extremely rich. Hard to get up to full speed. Same thing its been doing all along.

I took a tiny flathead screwdriver and stuck it in the venturi and covered up the top of the emulsion tube while running the engine up in RPM. Runs 100% better. Smooths out, stops running so rich.

HOW? How can it be pulling all the fuel it needs to run up in RPM, under load, through the idle circuit?? Where else could it be coming from? I can look in the barrel of the carb when I've got the tube covered up, and no fuel is coming out from the top while its covered with the screwdriver, OR from around it?

And what are the chances that BOTH the carb I got with the engine and the used one I bought have this SAME problem????

I am BEYOND confused.

 

[dieselfuelonly]

Interesting development!!

I was comparing carbs again. Looked at the fuel well. Carb that came with the motor has a much larger idle restriction/jet/whatever you want to call it in the plastic well than the old carb. Both are #50 for the main jet, but the little brass tube that connects to the tube for the idle circuit with the small piece of fuel hose is smaller on this other well. Maybe it's the wrong one? Maybe that's allowing it to suck too much fuel through the idle circuit!?! Swapping them out and... fingers crossed for a change.

 

[dieselfuelonly]

Its running.... 100% better. Holy crap, that might have been it. Someone replaced the well with one from a different carb that had a bigger idle restriction tube in it. I never tried running the well from the eBay carb, I always just used the one that the carb the engine came with had in it. Can't verify from the parts page WHAT the number is supposed to be on bottom of the well. Either way, HEADED TO THE LAKE FOR A TEST RUN!!

 

[dieselfuelonly]

Update from the lake. Still running rich. Been playing with the carb a bunch. Finally took the silencer off and found it runs a ton better with air getting rammed into the carb once you get moving. Got some video. Will upload when I get back. I really wish I had a known good carb specific to this exact year and model of engine to test with.

 

[oldboat1]

Look for an adjustment needle on or near the top of the powerhead -- would allow you to adjust the mix leaner (clockwise).

 

[dieselfuelonly]

Look for an adjustment needle on or near the top of the powerhead -- would allow you to adjust the mix leaner (clockwise).

Uhh on top of the powerhead? These only have one adjustment that is on the plastic cover on top of the carb . Am I missing something?

 

[saltchuckmatt]

Uhh on top of the powerhead? These only have one adjustment that is on the plastic cover on top of the carb . Am I missing something?

No, your not. Not sure what he's talking about

 

[dieselfuelonly]

No, your not. Not sure what he's talking about

Good to know, lol.

So here's where I'm at now:

Out on the lake, at first it started right up and idled well, would run fine through the lower-mid rpms, and then start 4-stroking as soon as it got into the higher-mid RPM range, and couldn't build up enough RPM to get up on plane it was 4-stroking so bad.

After a while of messing around I took the silencer box off and was going to cover the emulsion tube to see if it was getting too much fuel through the idle circuit at WOT. It started refusing to idle after that (whether that's related, or perhaps the idle circuit somehow got clogged with some debris, I don't know yet), but what happened next was very interesting - with the silencer box off, the engine would run so much better at full RPM. No more 4-stroking, it would easily get the boat up on plane and I think I saw 16-18MPH on the Garmin. But it refused to idle after that.

One part of me says that with the silencer box off, it was getting much more air rammed into the barrel of the carb which helped lean the mixture out and made it run better. This wouldn't explain why the engine would no longer idle though.

Another part of me says it's just a fluke and having the silencer box off is completely unrelated, but the idle circuit got clogged, and that was what caused the mixture to lean out. This would explain why it would no longer idle. It ran great at higher RPM now because the mixture was much leaner.

But I keep coming back to... why??

Is the carb just configured completely wrong for this engine?

My carb uses this little "nozzle well" that sits in the center of the bowl. It has a main jet with #50 stamped on it (Evinrude calls this the "high speed orifice" on the parts page), and which matches the parts page saying the 8HP should have a 50, while the smaller 6HP would use a 38.

On the bottom of the nozzle well, there is a #2 molded into the plastic next to the idle orifice. I swapped this nozzle well with the one from the carb I bought off of eBay which had #4 molded into it, and it had a smaller idle orifice. That was the one I ran on the lake today, thinking that the smaller orifice might introduce less fuel though the idle circuit and help lean things out.

It did make a difference compared to how this thing has been running lately, however it still seems too rich.

Can anyone confirm what number should be stamped on the bottom of the nozzle well for the 8HP? Here is a picture of the "#2" nozzle that was in the carb the engine came with.

I can order a new one for $35, but before I go spending $35 on a 8 cent piece of plastic with a 10 cent brass tube molded into it, I figured I might ask here in case I already have the right one.

 

[saltchuckmatt]

Good to know, lol.

So here's where I'm at now:

Out on the lake, at first it started right up and idled well, would run fine through the lower-mid rpms, and then start 4-stroking as soon as it got into the higher-mid RPM range, and couldn't build up enough RPM to get up on plane it was 4-stroking so bad.

After a while of messing around I took the silencer box off and was going to cover the emulsion tube to see if it was getting too much fuel through the idle circuit at WOT. It started refusing to idle after that (whether that's related, or perhaps the idle circuit somehow got clogged with some debris, I don't know yet), but what happened next was very interesting - with the silencer box off, the engine would run so much better at full RPM. No more 4-stroking, it would easily get the boat up on plane and I think I saw 16-18MPH on the Garmin. But it refused to idle after that.

One part of me says that with the silencer box off, it was getting much more air rammed into the barrel of the carb which helped lean the mixture out and made it run better. This wouldn't explain why the engine would no longer idle though.

Another part of me says it's just a fluke and having the silencer box off is completely unrelated, but the idle circuit got clogged, and that was what caused the mixture to lean out. This would explain why it would no longer idle. It ran great at higher RPM now because the mixture was much leaner.

But I keep coming back to... why??

Is the carb just configured completely wrong for this engine?

My carb uses this little "nozzle well" that sits in the center of the bowl. It has a main jet with #50 stamped on it (Evinrude calls this the "high speed orifice" on the parts page), and which matches the parts page saying the 8HP should have a 50, while the smaller 6HP would use a 38.

On the bottom of the nozzle well, there is a #2 molded into the plastic next to the idle orifice. I swapped this nozzle well with the one from the carb I bought off of eBay which had #4 molded into it, and it had a smaller idle orifice. That was the one I ran on the lake today, thinking that the smaller orifice might introduce less fuel though the idle circuit and help lean things out.

It did make a difference compared to how this thing has been running lately, however it still seems too rich.

Can anyone confirm what number should be stamped on the bottom of the nozzle well for the 8HP? Here is a picture of the "#2" nozzle that was in the carb the engine came with.

I can order a new one for $35, but before I go spending $35 on a 8 cent piece of plastic with a 10 cent brass tube molded into it, I figured I might ask here in case I already have the right one.

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

 

[dieselfuelonly]

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

Interesting... I have a 2 and a 4. Wonder if the 3 is in between or if there's no correlation.

 

[saltchuckmatt]

Interesting... I have a 2 and a 4. Wonder if the 3 is in between or if there's no correlation.

It's a conundrum. Do you have your little rubber gasket in the bottom of the bowl that goes up against it?

 

[dieselfuelonly]

It's a conundrum. Do you have your little rubber gasket in the bottom of the bowl that goes up against it?

Yep, got one on bottom and a ring on top that seal it to the aluminum body.