I have a 2004 90HP Honda outboard with 100hrs that runs rough at idle and intermediately misfires at idle and hire revolutions. I have installed new spark plugs, fuel filter inside the outboard, water/fuel separator filter and cleaned the carburetors; and I still have the same problem. Any suggestions/recommendations on what to check for? Thanks.
90HP Honda rough idle and misfire
- Thread starter akhamsi
- Start date
How old is the gas coming into the filters from the tanks? Is there any indication of water in it?
Have you checked the compression on all the cylinders? What was it and was it even from cylinder to cylinder?
Did all of the plugs you took out look the same?
Were any wet, carboned up or covered with oil, etc?
If you run the motor at night in the dark with the shroud off, can you see any evidence of shorting on the ignition wiring or plugs from observing blue flashes?
Did the carburetor clean-out involve a complete cleaning out of the jets, draining of the bowls, and replacement of any necessary gaskets? How about setting the float levels and adjusting the carburetor synchronization with vacuum gauges?
Does the missing occur only with the engine in gear (with a load on it), or in neutral as well at low and somewhat higher rpm?
I wonder if you could up a timing light on the motor and test to see if each plug is firing by moving the plug lead from plug to plug to see if the misfire can be seen as a non-flash in the sequence of flashes; e.g., when the misfire occurs, does the light not flash?
Have you run any carb cleaner and/or carbon cleaner through the engine, such as SeaFoam?
Do you have a Honda Shop Manual for your model? How difficult is it to check the engine timing?
Have you allowed the motor to warm up throughly to get any condensed water out of the electrical system, etc?
Many of our fellow C-Brast will also chime in on this, I'm sure!
Here's another source to ask:
Ask a Honda Mechanic
Honda.JustAnswer.com 8 Honda Mechanics Are Online! Ask a Question, Get an Answer ASAP.
Good Luck!
Maybe someone with a manual for your motor can suggest some more leads to follow up on...
Have you checked the compression on all the cylinders? What was it and was it even from cylinder to cylinder?
Did all of the plugs you took out look the same?
Were any wet, carboned up or covered with oil, etc?
If you run the motor at night in the dark with the shroud off, can you see any evidence of shorting on the ignition wiring or plugs from observing blue flashes?
Did the carburetor clean-out involve a complete cleaning out of the jets, draining of the bowls, and replacement of any necessary gaskets? How about setting the float levels and adjusting the carburetor synchronization with vacuum gauges?
Does the missing occur only with the engine in gear (with a load on it), or in neutral as well at low and somewhat higher rpm?
I wonder if you could up a timing light on the motor and test to see if each plug is firing by moving the plug lead from plug to plug to see if the misfire can be seen as a non-flash in the sequence of flashes; e.g., when the misfire occurs, does the light not flash?
Have you run any carb cleaner and/or carbon cleaner through the engine, such as SeaFoam?
Do you have a Honda Shop Manual for your model? How difficult is it to check the engine timing?
Have you allowed the motor to warm up throughly to get any condensed water out of the electrical system, etc?
Many of our fellow C-Brast will also chime in on this, I'm sure!
Here's another source to ask:
Ask a Honda Mechanic
Honda.JustAnswer.com 8 Honda Mechanics Are Online! Ask a Question, Get an Answer ASAP.
Good Luck!
Maybe someone with a manual for your motor can suggest some more leads to follow up on...
T.R. Bauer
New member
akhamsi":268v4odh said:
Well, you covered the simple stuff. How does it run on full throttle? It is still easily planes, has great power, and doesn't use oil, then it probably is not a serious engine problem. However, valve adjustments can cause what your engine is doing, but normally because they are too tight, not too loose. And, it happens right after someone adjust them. If nobody has messed with them lately, it probably is not the valves.
I would seriously look at your carbs again. They can be a pain and they are sensitive to dirty gas as well as old gas. The idle circuits are very small, and something most inexperienced people miss when cleaning a carb after the disassembly process. Often times, even when you try to clean them, they don't get as clean as you would hope and the engine runs horribly; especially at idle speeds.
But, probably the easiest thing that you could right now is run the engine with fresh gas with carb cleaner/fuel injection cleaner in the gas itself. Surprisingly, this actually works sometimes, but takes several hours to do its magic. I use this remedy first on one of my picky 45s that likes extra mechanical attention from me (I have a needy one) before I get out the wrenches.
With not seeing it and not being able to tinker with it, if this were Vegas I would bet the whole stack of chips on something related to fuel and dirty carbs.
Almas Only
New member
Any 2004 with just 100 hours has been sitting around a LOT, and can be expected to have some gunk in the fuel system. Here's what I suggest you do to begin with. Where you end up depends on what you find.
Remove the motor cover, and with the engine at idle, check to be sure that there are no major fuel leaks around the motor head. There probably aren't, or you'd have noticed a large explosion. But, check just to be sure.
Then, put on a pair of thick leather gloves, and beginning at the top, and working down, pull the spark plug caps from the plugs, one at a time, separating the cap from the plug by a couple of inches so the spark doesn't arc across the gap, and fire the plug.
If the rpm begins to fall off, put the cap back on right away - that plug was firing, and the fuel in that cylinder was burning. If the rpm is not affected by a cap being pulled, or if the rpm drop off is significantly less than that of the other cylinders, that cylinder was not firing anyway, and you have a spark or fuel problem associated with that cylinder.
Hopefully, once you've done this drill, you will know which cylinders are firing, and which are not. Repeat this drill a few times, and you will know whether the problem is consistent with one or more cylinders. Now, you can form a few conclusions.
First, the gas you're pulling from the tank is good. It is consistently burning in three of the four cylinders, and should be burning in the fourth.
If you changed the plugs, and are observing the same condition, you probably don't have a problem with the plugs. Although you could have an electrical problem with the spark to the affected cylinder or cylinders, I would probably look elsewhere, first. My reason is that you have a near new motor, and electrical problems don't generally result from low use. Fuel problems, on the other hand, seem to come with low use.
Assuming you have a fuel problem, I'd crack the drain screw at the bottom of the float chamber of the affected cylinder or cylinders, and let the fuel drain out onto a rag. Then retighten the screw. While you're there, you probably should drain the other three, given the low usage hours. Then reprime and restart the motor. If the problem goes away, you had some gunk or water in the bowl.
If the problem persists, figure you've got some plugging in the carb. Dump some Stabill (sp?) into the fuel, and run the motor for a few hours.
Let us know whether the problem goes away, and we'll go from there.
Good luck.
Remove the motor cover, and with the engine at idle, check to be sure that there are no major fuel leaks around the motor head. There probably aren't, or you'd have noticed a large explosion. But, check just to be sure.
Then, put on a pair of thick leather gloves, and beginning at the top, and working down, pull the spark plug caps from the plugs, one at a time, separating the cap from the plug by a couple of inches so the spark doesn't arc across the gap, and fire the plug.
If the rpm begins to fall off, put the cap back on right away - that plug was firing, and the fuel in that cylinder was burning. If the rpm is not affected by a cap being pulled, or if the rpm drop off is significantly less than that of the other cylinders, that cylinder was not firing anyway, and you have a spark or fuel problem associated with that cylinder.
Hopefully, once you've done this drill, you will know which cylinders are firing, and which are not. Repeat this drill a few times, and you will know whether the problem is consistent with one or more cylinders. Now, you can form a few conclusions.
First, the gas you're pulling from the tank is good. It is consistently burning in three of the four cylinders, and should be burning in the fourth.
If you changed the plugs, and are observing the same condition, you probably don't have a problem with the plugs. Although you could have an electrical problem with the spark to the affected cylinder or cylinders, I would probably look elsewhere, first. My reason is that you have a near new motor, and electrical problems don't generally result from low use. Fuel problems, on the other hand, seem to come with low use.
Assuming you have a fuel problem, I'd crack the drain screw at the bottom of the float chamber of the affected cylinder or cylinders, and let the fuel drain out onto a rag. Then retighten the screw. While you're there, you probably should drain the other three, given the low usage hours. Then reprime and restart the motor. If the problem goes away, you had some gunk or water in the bowl.
If the problem persists, figure you've got some plugging in the carb. Dump some Stabill (sp?) into the fuel, and run the motor for a few hours.
Let us know whether the problem goes away, and we'll go from there.
Good luck.
Matt Gurnsey
New member
We have a customer with a smaller carburated Suzuki with a similar problem. ANother low hour engine that had sat a lot. Corrosion in the carb was the culprit, and the carbs had to be replaced, as they could not be cleaned out.
We recommend running Sta-Bil marine (the blue stuff) all year long. Sta-Bil has a regular concentration and a winterization concentration. We figure it's cheap insurance, along with a fuel / water separator to maintain that motor on the back of the boat.
We recommend running Sta-Bil marine (the blue stuff) all year long. Sta-Bil has a regular concentration and a winterization concentration. We figure it's cheap insurance, along with a fuel / water separator to maintain that motor on the back of the boat.
cbull":1b8c7eks said:
(My use of red for emphasis.)
Very true! But unlike an auto, I don't think a specific engine can be easily retrofitted with fuel injection, since it's a complete computer controlled system, making the fuel injection fix simply to get a different, newer, more modern engine, which ='s $$$. (You probably know this, just pointing it out for anyone that doesn't.)
Joe. :teeth :thup
I should have said a brand new shiny fuel injected 90hp suzuki. The 10% ethanol is causing lots of problems. Star tron they say is helping. The shop says with my 90 they can not get the vacuum the same on all carbs. They also said ethanol causes any water is the tanks to suspend in the fuel causing it to by-pass the f/w separator. I do not buy this. I think there are many shops out there using the fuel issue to rebuild carbs prematurely. Always try sea foam treatment before taking to shop. This could save $$$$$$$$$$$$$$$$$$.
If it will run, I'd dump a can of SeaFoam (available at most auto stores, about 9 bucks) in 6 gallons of fresh gas and run it. If this treatment is going to work, you should get some indication of improvement after 15 or 20 minutes, but it may take a few hours running time to clean up completely. My 75 is pretty finicky if it's been getting little use, or sitting for more than about three weeks. The SeaFoam can reads like one of those impossible miracle cures, but amazingly it does work!
Mike
Mike
T.R. Bauer
New member
Sea Wolf":29vmfjeg said:
Joe, if you think retrofitting a honda auto (or just about any for that matter) that was originally a carb engine is easy to change to fuel injection, you have been grossly mislead. You are talking about a huge pile of fuel system parts, fuel tank modifications, fuel pumps, hard fuel line modifications, about 3500 bucks in sensors, and replacing the entire intake system. That is if any of it even bolts on as carb engines and EFI engines are normally apples and oranges. Why do I know this? Because I stuffed a Vortec 350 in my 1983 Toyota 4x4 pickup. And then, after that (which took almost a year) I put an EFI 460 in my 78 Ford F250. When I say "I", I literally mean I as I built these up and intalled them myself. It is a sick little hobby I have. I like to make slow things go fast. But, to the point; it wasn't cheap and it wasn't easy. And this was with engines that were designed to have fuel injection. In case you are wondering, the toyota is scary quick and fast as hell with 400 plus hp. Just like the outboard, it is easier and probably cheaper to just buy another car with fuel injection.
But with this said, the carb is not the problem. It is how you are storing it. If you drain them before you store it for prolong periods, then the likeliness of this happening to your outboard is very slim. It is also very wise to store fuel with a fuel stabilizer in it as it does go bad. Others have posted an ignition problem and you certainly could have one, but your symptoms reek or a fuel problem.
T.R. Bauer
New member
cbull":263f3yel said:
If they can't get the vacuum the same you have a problem. And, if you have good compression, you have a vacuum leak at the carb base gasket, or somewhere on the carb itself. There is no reason why the should not be able to synchro the carbs. In fact, if you have a problem, there is no point in even trying.
T.R. Bauer":1shih579 said:
No, I don't think it is an easy process, especially as systems become more complex and sophisticated. I know EFI with individual port injection and all the computer sensors, manifolds, and so forth is overwhelmingly difficult to add on to an existing engine.
I was told once by a mechanic at an RV dealership that he could add fuel injection to my 460 Ford motor in my motor home, but certainly wouldn't be a complex or carefully monitored system. More of a "Spray and Go" simplified system, so to speak, just substituting for the carburetor.
Surprisingly enough, the carburetor in the 460 never seems to give us any trouble, although part of this is understandable since we start it every 4-6 weeks to charge the batteries and heat the engine up to void condensation, etc.
This seems to contrast somewhat with some of the marine experiences with carburetors, but the size of the jets and other passages in the larger engine and the more frequent flushing from the starting intervals would account for some of the differences, as would the storage away from the marine environment.
Thanks for catching the over-generalization! I guess I'll have to start previewing my posts more carefully for those kinds of statements. Sometimes the rush to get it done and on to the next subject leaves the more casually made minor points unedited for complete technical correctness! :lol:
Fun talkin' with ya'!:wink
Joe. :teeth :thup
Check the tiny emulsion tubes in the carbs . When they clog , they split and the motor wont run right even after a "carb cleaning" Its not obvious unless you deal with alot of Hondas . Then you always look for it .Once its running right draining the carbs is the right answer ! New fuel sucks .
The Suzuki carb problem with the small ones [25s and 30s]is the needle and seat in the carbs [I know, I have one and it took a long time and our super sleuth and carb master Alan to figure it out] They were bad on a brand new set of replacement carbs right out of the box
Marc!
The Suzuki carb problem with the small ones [25s and 30s]is the needle and seat in the carbs [I know, I have one and it took a long time and our super sleuth and carb master Alan to figure it out] They were bad on a brand new set of replacement carbs right out of the box
Marc!
T.R. Bauer
New member
Wefings":s3epifpv said:
Marc,
Thanks for reminding me what those tubes are called. I hate those tubes, they are a spawn of the devil himself....
Tim
T.R. Bauer
New member
T.R. Bauer":2llrmwyd said:
I found a source of help for Honda outboard owners. It has tons of discussions about solving problems with various sized engines, from what I can tell preliminarily.
Take a look and see what you think.
Honda Outboards
This could be a pretty good find!
It also has discussion forums for all the other major outboard brands too!
And if you scroll down on the last link, there are discussions on I/O's, Inboards, and Diesels, too!
Joe. :teeth :thup
Take a look and see what you think.
Honda Outboards
This could be a pretty good find!
It also has discussion forums for all the other major outboard brands too!
And if you scroll down on the last link, there are discussions on I/O's, Inboards, and Diesels, too!
Joe. :teeth :thup
Marc-
You got my curiosity going as to what those emulsion tubes looked like and were all about, so I looked for a photo. Couldn't find one of a Honda outboard, but the one below is from a Honda motorcycle, and is probably somewhat similar and illustrates why the little bugger holes are so sensitive to gas quality issues.
I'm guessing these bridge across the throat of the carburetor, are enclosed in the carburetor throat's walls on either end, and fuel is fed out of the little holes into the intake air, with the little holes intended to make the droplets smaller than regular jets, and thus "emulsify" it (?)
Thanks for the ideas and fun comments!
Joe. :teeth :thup
You got my curiosity going as to what those emulsion tubes looked like and were all about, so I looked for a photo. Couldn't find one of a Honda outboard, but the one below is from a Honda motorcycle, and is probably somewhat similar and illustrates why the little bugger holes are so sensitive to gas quality issues.
I'm guessing these bridge across the throat of the carburetor, are enclosed in the carburetor throat's walls on either end, and fuel is fed out of the little holes into the intake air, with the little holes intended to make the droplets smaller than regular jets, and thus "emulsify" it (?)
Thanks for the ideas and fun comments!
Joe. :teeth :thup