Any outboard mechanics?

[Stein]

I have a Yamaha 4MLH that runs like garbage at low idle - not so good for sockeye.  I drained all the gas, replaced it with fresh ethanol free treated with Seafoam and cleaned the carb (twice, the second time more thorough), changed the oil and cleaned and checked the plug gap.  The engine is a 2006 and looks to be pretty much unused. 

It idles extremely rough and bogs down a bit until it gets up in rpms and then seems to run great.  I ran the carb screw all the way in to all the way out and it doesn't seem to make any difference (did this out of gear in the driveway as well as under power in the boat at the lake).  It does much better since the carb clean and fresh gas, but it still isn't running that well.

I also took the fuel pump out and put it back together and checked it by pulling the starter cord.  I also placed the fuel tank high above the motor and it doesn't make any difference - I think the problem isn't there.

I can run the boat ok at 3 mph or greater but anything under that is not so great.  The guy I bought my boat from bought it new and said it never ran that well.  He has receipts for several tune ups but they didn't fix whatever is wrong.

Any ideas, my very limited knowledge has been used up?

[TheHunt]

The only thing I can think of is the fuel lines.  I would also wait to see what the experts say on this site.

[lokidog]

The only thing I can think of is the fuel lines.  I would also wait to see what the experts say on this site.

I would try new fuel lines as well, they tend to deteriorate from the inside when gas sits in them, especially with the ethanol.  I have had a dark sort of varnishy stuff in there as well as bits of rubber.   

Good luck. 

[Fishnclifff]

FUEL FILTER.

The new ones have a chitty element that melts and clogs up.

I change mine at least twice a year.

[Bmcox86]

Fuel filter.

[BigGoonTuna]

you might want to find someone who has an ultrasonic cleaner and run the (fully disassembled) carb through it, then do a full rebuild.  your issue sounds like a partially blocked idle circuit to me, something might be lodged in there.  it doesn't sound like a fuel filter, if that was an issue the problem would get worse as you throttled up.

[Stein]

you might want to find someone who has an ultrasonic cleaner and run the (fully disassembled) carb through it, then do a full rebuild.  your issue sounds like a partially blocked idle circuit to me, something might be lodged in there.  it doesn't sound like a fuel filter, if that was an issue the problem would get worse as you throttled up.

Thanks.  What parts are replaced during a rebuild, the seals and gaskets?  There aren't many parts in a 4 hp carb.

[L-ofalab]

you might want to find someone who has an ultrasonic cleaner and run the (fully disassembled) carb through it, then do a full rebuild.  your issue sounds like a partially blocked idle circuit to me, something might be lodged in there.  it doesn't sound like a fuel filter, if that was an issue the problem would get worse as you throttled up.

I agree with low speed circuit. I thought someone was recommending adding a fuel filter instead of it being dirty, either would be good to add or clean but because it runs OK at  higher RPM that would probably not be the problem. I used to work on lots of motors of all kinds and there used to be 2 carb needles, HI & LO. Many motors have gotten away from that design and frequently there are only pre set jets where there is no adjustment. Many carbs are sealed with plugs that are tough to remove without ruining the carb but your plugged LO speed passage could be where it is not cleanable and only a new carb would help.

[Stein]

Thanks everyone.  I picked up an ultrasonic cleaner on clearance at Midwayusa and we'll see if that works.  A new carb is $205, so I'm hoping that isn't the cure.

[L-ofalab]

A good quality ultra sonic cleaner would cost more than $200. If you didn't pay that much it probably won't work. I bought a couple from Harbor Freight and returned them after seeing how poor they worked. When you put stuff in a quality cleaner and turn it on it is easy to see the stuff coming out. We used to put wrist watch metal bands in ours and it was amazing how much dirt came out of the links.

[Stein]

We'll find out, Midway has a great return policy.  Should be here Friday.

[Kc_Kracker]

I was for 10 years. run whatever you want thru it, it wont matter, you need to strip the carb down and scrub it out. if theres junk in the jets and there usually is it wont idle down nice. if you need help yank the carb off and bring it to me.

[pilebuck]

Take it in and get it fixed unless its something simple boat motors are a pain to work on period.....Good chance the carb needs to be rebuilt. I have a Johnston 3 cylinder seahorse 70 hp with 3 carbs sent the motor in and got them all cleaned out and rebuilt and tuned again anything to do with boats r expensive break out another thousand =boat 

[Kc_Kracker]

outboards are the easiest thing on the planet to work on, take it into a shop right now you wont see it til after the season ends

[Gobble Doc]

KC,

I've got a 40 HP Yamaha and I too am intimidated to tear the carbs apart.  I took mine to BaySide and it was indeed expensive.   I think there are 3 carbs.  Are there timing adjustments to make when you reassemble?  Or is it really as easy as taking it all apart and cleaning and then just reassembling? 

[Kc_Kracker]

no timing adjustments to make. but they are synced, you want to tag them and install them back in the same place and dont swap any linkage around. just pull them off, strip them and clean them, except any linkage and butterflies there is no need to remove that stuff. in the bottom you will have a plug that holds the jet in, that plug has a hole in it the size of a hair, thats usually whats plugged.

[deltaops]

All of what KC has said so far. 

Mine is now doing the same thing and I am about ready to pull the carbs off and clean them. pretty easy and saves on the wallet.

[Kc_Kracker]

lord, do we need to have a hunt wa carb party? 

[quadrafire]

That would be for the dyslexic bunch that started out for the crab gathering

[Kc_Kracker]

i refuse to be a part of helping ya'll with yer CRABS

[Gobble Doc]

 

[JackOfAllTrades]

If the fuel mix adjustment does nothing... Idle circuit venturi or the jet is likely gummed up. Could still be a vaccume leak but it would probably idle high and stumble as you increased throttle. Butterfly adjustment?  I don't know why people are intimidated by carburetors. Note your steps to taking it apart. Right down to how many turns a screw takes to get out. Use your smart phone to take photos as you disassemble. Take it apart on a clean bench with a bath towel spread out. Don't lose any parts!
 
-Steve

[deltaops]

If the fuel mix adjustment does nothing... Idle circuit venturi or the jet is likely gummed up. Could still be a vaccume leak but it would probably idle high and stumble as you increased throttle. Butterfly adjustment?  I don't know why people are intimidated by carburetors. Note your steps to taking it apart. Right down to how many turns a screw takes to get out. Use your smart phone to take photos as you disassemble. Take it apart on a clean bench with a bath towel spread out. Don't lose any parts!
 
-Steve

 

I am not intimidated as I have taken quite a few a part myself. From cars to small engines, they are pretty easy to do. Just remember how you took them out and a part and reverse the order when putting them back together.

If you are unsure, take lots of pictures during the process. 

[pilebuck]

Yen take it in now and it will take forever maybe that's why u make sure way ahead of time its wrkin like going hunting opening day and sighting ur scope  And for easy to work on depends on the person I worked in the marine industry all my life and there r things I will do and things I won't. Outboards r a pain in the a__ period esp older ones where parts r hard to get.youtube helps 

[Stein]

My motor has been to the shop 3 times (previous owner).  I did a bunch of research and found that Krud Kutter is probably one of the better aluminum solvents to use and Lowes sells it.  I'm going to tear it apart all the way and put all the metal parts into the ultrasonic cleaner tomorrow night for several cycles, reassemble and see how that goes.  I'll post back with the results.

[L-ofalab]

Did your ultrasonic cleaner work? It has been a week I'm waiting to hear how well yours worked, the Harbor Freight ones were weak.

[Stein]

OK, looks like that did the trick.  I started with hot water and maybe 1-2 cups of Krud Kutter in 2 L total of solution.  The ultrasonic was just short of deep enough to submerge the carb.  I ran it for five 4 minute cycles per side and then noticed that the middle of the pan seemed to have better action.  So, I ran it a few more cycles in the middle.  Long story short, I ran it many, many cycles.

There were a few pieces of junk that floated out for sure.  All parts look like new.  Assemble and it fired right up.  At the lake, it ran great except the mixture screw has a tendency to back out, so the o-ring is probably worn and I need to replace that.

The only problem I had was when I tried to get it to idle crazy slow for sockeye. 

I also ran several other things through the cleaner.  I think it isn't the most powerful, but for the price it seems to work well.

[Kc_Kracker]

if it womnt idle crazy slow then its either that AFM o-ring leaking air, or you missed a plugged port in the carb, or adjustment, those are the only 2 things that really affect low idle, oh and good plugs

[bloodhound]

keep in mind if you do the carbs on your big motor youll have to buy a vacuum mate to set them up. its easy to do but the tool isnt too cheap.

for all those out there that recommended changing the fuel filter.......

 FUEL FILTERS DON'T FIX ENGINES!!!!!  IN ALL MY YEARS AS A MECHANIC AND I AM A OUTBOARD MECHANIC, NEVER EVER, EVER,EVER,EVER ECT HAVE I SEEN CHANGING A FUEL FILTER FIX A MOTOR ISSUE.

except.... on an optimax where the filter has a sensor in it and when the filter has to much water in it it will sound an alarm, changing the filter will shut off the alarm.

[Stein]

if it womnt idle crazy slow then its either that AFM o-ring leaking air, or you missed a plugged port in the carb, or adjustment, those are the only 2 things that really affect low idle, oh and good plugs

By "crazy low" I mean like 300 rpm.  I could see the blades in the prop spinning.  I was trying to get down to .5 mph with a slight wind.  It runs great at a more normal idle.

[Stein]

keep in mind if you do the carbs on your big motor youll have to buy a vacuum mate to set them up. its easy to do but the tool isnt too cheap.

Is that only needed on multi-carb setups (I hope)?  My 40 Merc has a single carb that is now sitting in pieces on my bench waiting for the rebuild kit to arrive.  I'm also rebuilding the fuel pump, checking the reed valves, replacing the fuel filter, fuel lines, fuel bulb and thermostat as well as new plugs.  It's a 2004, so rather than chase things for the next few years I figured I would go through most of what can be replaced easily and for just a few bucks.  I think I only spent about $100 for everything.

[bloodhound]

yah only multi carb setups

[BigGoonTuna]

FUEL FILTERS DON'T FIX ENGINES!!!!!  IN ALL MY YEARS AS A MECHANIC AND I AM A OUTBOARD MECHANIC, NEVER EVER, EVER,EVER,EVER ECT HAVE I SEEN CHANGING A FUEL FILTER FIX A MOTOR ISSUE.

except.... on an optimax where the filter has a sensor in it and when the filter has to much water in it it will sound an alarm, changing the filter will shut off the alarm.

my favorite quote by customers when i worked in the chainsaw repair business, "i think it just needs a tune up"   i always said there's two kinds of tune ups i'd do, the ones where someone says "give it a tune up"(meaning nothing was wrong and i was just gonna take their money to put a spark plug in) and "i think it needs a tune up" which meant it probably didn't run and could be anything from a fuel line to ignition coil or even a top end.

[Stein]

Well, I rebuilt the carb, replaced fuel lines & filter, new plugs, new thermostat & diaphragm and fuel line & bulb to the tank and....it runs about the same.  Actually, above 1500 rpm it runs like a sewing machine.  Below that, an 80's Harley.

I check the manual and ended up finding a problem with the top CDM, so I ordered a replacement that should be in Friday.  It actually makes sense because i was getting much worse fouling in the top cylinder at idle which would correspond to a bad CDM.

I don't know enough about CDMs but apparently there can be failure that only affects low rpm operation.