Intermittent slowness

I am new to owning an outboard motor, but have a good level of mechanical experience. I am having trouble with a (new to me) Honda outboard. I have been reading bunches, and can't figure out my problem.

2006 Honda 8HP 4 stroke, bought on consignment from a dealer. Dealer checked the engine, compression is good, motor not used much. (It does look brand new)

Upon using the motor, it was fine, ran exactly as I expected. Brings the boat up out of the water, and probably achieves close to 15mph. New gas, which is only a week or so old.

Used the boat one day, and parked it in the water. It was fine on the short trip there. Next day, I went to take it fishing with my daughter, and the boat started fine, ran fine, but would not accelerate or rev up past about 1/4 throttle. Idle was a little less than ideal, but didn't really stall out unless it idled for a good amount of time. I thought maybe there was something clogging the cooling system, so I took the boat home and ran it in a tank of clean water. Checked the oil, it appears to be correct. Reading led me to believe maybe it was not getting adequate fuel. Next time out, the boat ran perfectly, all the way up to full throttle. Took the boat home. Filled the tank up again with new gas.

Trip prior to last, I disconnect the fuel line to see what happens when I run the boat dry while it is running fine. It goes fine to the very end and shuts down. I put it on the trailer with the trolling motor.

Last trip by myself, after running it dry, boat started right up, parked at the dock, shut it down. Jumped back in, boat ran great for about 10 miles. Stopped to fish. Started right up to go home, but boat would not run past about 1/4 throttle. It doesn't bog down, it doesn't sound bad, just won't go fast. I can turn the throttle up a couple clicks, and then after that it makes no difference how far it's turned. Cruised back the 10 mi or so very slowly. Toward the end it was getting a tiny bit worse, but only after the hour or so it took to get back. I tried stopping, and re-priming. I tried pumping the primer while running, no effect. Put the boat on the trailer and came home.

After much reading, I checked the fuel supply. The bulb is pumping into the filter, which is about 1/2 full of gas. The tank looks clean, the dip tube appears to be fine. I thought maybe it was cracked, but it has run fine on 1/2 tank, and bad on full tank, so I think that's not it.

The bulb doesn't firm up like I think it should, but I can see it is pushing gas, and have confirmed the gas is getting all the way to the carb plug. Fuel supply lines appear in good condition. I am opening the tank carburetor, the oil light is on, boat is peeing, and I think I'm running it exactly as the manual suggests, with the exception of trying the primer once while running slow. Throttle linkage mechanically functions perfectly.

I'm thinking maybe the bulb is bad, and have ordered a new one, but I'm not sure because the motor isn't really stalling or anything except at dead idle for extended period of time. Also, running with the fuel line disconnected when it was running good didn't seem to bother it, which I would think a bad bulb would have choked it out almost immediately in that situation (it took a good few minutes to burn up what was in the fuel line). It's like the motor is either 100% or 25%, with nothing in between, and this can be apparently be caused by something as simple as shutting it down to fish an hour, and then restarting. Not sure if something is clogging the carburetor, but that also doesn't seem right to me, because it runs fine, even when it won't hit full throttle, and there appears to be no variation except it runs full bore, or doesn't.

Any diagnostic ideas or knowledge on why this is happening?

Need first to determine if it is spark or fuel.

The bulb should get hard when you squeeze it before you start the motor. So, it could be bad or the float could be stuck in the carburetor. If the float was stuck, you would see fuel leaking out of the carburetor. So, if you do not see fuel, the float is probably not an issue.

When you put your new bulb on, make sure the arrow is pointed toward the engine. Also, when you pump it, hold the bulb with the arrow pointing up vertically. It works better that way.

If the motor is manual start (not electric start), try pulling out the choke (enrichener) to see if it makes any difference. If so, then you may be looking at a fuel issue.

One other simple thing to do is put new spark plugs in the engine. If they are Denso brand, I would change them no matter what to NGK CR5EH-9. No substitutes. It is possible that you have a bad plug and you are only running on one cylinder when the problem occurs.

You say that the oil looks ok. Make sure that the oil level is about 1/4" below the full mark. Too much oil is not good.

I am sure others will jump in with more things to look for....but the above is for starters. Intermittent problems are the worst to solve.

Mike

Thank you for the reply.

When I pulled the choke while the engine was behaving badly, it choked out the motor almost instantly; like you would expect.

The spark plug in the motor is NGK DR5HS. Which is what the manual recommends. Is this what I should be using, or is the plug you have listed better? I could only get the top one out, because I don't currently own an 18mm plug wrench, but the top one looked pretty crummy, so I'll replace them. Probably original. I didn't have the gauge with me, but the gap looked small too, even for .024"

The dipstick had more measurements than I have ever seen. It was about 80% of the way between "too little" and "full".

Opps! Sorry....I assumed the wrong 8 HP. Honda had two different versions of the 8HP in 2006 and 2007. I thought you had the newer version.

It sounds like you have the older version, so the spark plugs you have in the motor would be the correct plugs.

I would still change them. They are cheap.

Another thing to check are the bolts holding the spark coil in place. It sometimes has a tendency to work itself loose. That grounding point is very important. Also, check any of the other bolts and nuts for ground wires around the coil area.

The long shot would be the cam shaft pulley springs. They may have rust or whatever on them and only allowing the timing to advance when it wants to....not necessarily when you want to accelerate. You could have to pull it to check it. You might want to remove the rubber grommet on top and just peek inside to see if there is anything obvious going on in there. Once you actually pull the pulley, you would have to reset the timing marks.

Mike

It's quite possible that it's only running on one cylinder at times. I agree that a plug change is in order. These twins run surprisingly smooth on one cylinder so it can be hard to tell except for the loss of power.

Also, I suggest that you manually drain the fuel from the carburetor instead of just "running it dry". Running it dry doesn't effectively get ALL the fuel out of the float chamber. Draining the carb with the drain screw will save you from having about twice as many carb contamination problems.

Keep an eye on the carb accelerator pump for sticking. The pump plunger is fitted through a small rubber bellows. You should be able to push the plunger down with your finger or see it being moved downward as you twist the throttle from idle. If it is siezed, it's probably NOT causing your current problem but it would indicate that it may be time to clean the carb due to mineral deposits. These little carbs are sensitive to deposits and draining them regularly will save you many headaches. If you intend to do your own wrenching, you will eventually want to own the Honda Marine Carburetion Manual. I thought I did a pretty dang good job at cleaning these carbs until hondadude talked me into getting the manual. GREAT BOOK! It will have you cleaning and repairing the carb PROPERLY the FIRST time.

Anyway, all the carb stuff is more FYI than anything. Change out the plugs and look at that pulsar coil advance mechanism under the cam pulley Mike told you about along with the coil mount bolts and all grounds you can see and, hopefully, your issue will clear up.

Thank you for the help guys. Ordered new plugs and the wrench I need since they don't have them local. Should be here Thursday.

Checked the spark coil and ground screw. 100% solid.

When you say drain the gas, does that mean every time after I run it, or if I am planning to run it again in the next week can I leave it, or what is the interval?

Also, I noticed tonight that if I pump fuel into the filter, it drains out of the line. I don't know how long this took. I'll say it had as much as 4 hours to dry up. What is normal?

If you're not going to use your boat for more than a couple of weeks, drain the carb. More often if you're unsure about the cleanliness of the fuel.

I worked at a dock that had old pumps and underground tanks. We found water in the gas when the rental boats started having problems. Of course the boss continued selling the contaminated fuel to private boaters to empty the tank even while he brought in clean fuel for the rentals.

That's why I wouldn't hesitate to drain my carb every outing. It's a personal preference sort of thing.

As far as your check valve holding, it theoretically should hold indefinitely. But they aren't perfect and will bleed off over time. That's why checking it periodically is wise. If the bulb is lying on the deck it will likely drain back quicker than if it is hanging in a vertical position.

A different thing to consider is, if you're using a quick disconnect fitting for the fuel line to engine, you need to check the the pin and valve in the connector halves for wear periodically. Just the action of plugging the fittings together can cause both to wear. But what really grinds on them is engine vibration. Over time the vibrations of the engine can wear the components to the point that the pin can't open the valve enough to allow for adequate fuel flow. It's another FYI thing I want you to know about.

Thank you. If I know the line is draining on it's own, do you think I should go ahead and replace the whole fuel line assembly, or just the bulb? Or wait until I get the throttle issue figured out? I know that it is capable of providing enough fuel to run at high/max speed for extended periods of time, as it has done so on many occasions. I am cautious to change several things at once, given my primary problem appears not to be dependent on that line... I am not against replacing worn parts, but I don't want to obfuscate the throttle problem by introducing new variables.

Well, if the check valve is leaking bad enough it COULD contribute to the loss of power. It can have your fuel pump starving for fuel. If you're not sure, replace the bulb. If the hose is old and hard replace that too. It will simply eliminate those items as cause for concern and shouldn't really cause you any confusion.

One thing that happens with old hoses is that they can break down on the inside and collapse or tear internally setting up a "valving" action that can slow or stop the flow of fuel to the pump. So renewing the hose and bulb every two or three years is money well spent.

Thank you!

So, my plugs came today. Checked the gap and put them in. Drained the carburetor and pumped the bulb.

Engine won't start. Tried full choke, half choke, about tore my arm off.

Tried adjusting idle screw. No luck. Gave it a shot of starter fluid, and it starts right up, but I can't keep it running. I think maybe I lost track of where I was on the idle screw. Manual is no help. Any ideas?

Will pick up a new bulb and line tonight.

I cleaned the port... forgot to mention

Try turning the mixture screw in until it gently bottoms out. Then back it out 2 full turns. That should put it in a "zone" to allow it to idle.

If it still won't start, I'm guessing you're gonna need to remove and clean your carb. Remember when I asked you to check the operation of the accelerator pump plunger? If you didn't, check it now. The engine doesn't need the pump to be operational to run but it does need that circuit clear. If the pump and plunger are sticking, it's a good indication that the circuit has crud in it.

Went ahead and pulled the carburetor to see if it was all varnished up. It is not. Tomorrow, going to replace the fuel line and bulb, and put the carburetor back on. Much better idea where the adjustment screw is now that I've seen it.

Any ideas why else it might not be cranking would be much appreciated!

I've been doing this a few years now and on many, many occasions I've had guys say they thoroughly cleaned the carb. In more than a couple of instances they've tried 5,6, 8,10 times! You cannot tell if the carb is in condition to run the engine by looking at it. There are a couple of critical performance checks it must pass regardless of how shiny it is. That's why I constantly recommend the Honda Marine Carburetion Manual for anyone doing their own work. It's what you can't see in the carb that can trip you up. But go ahead and try the hose and bulb before you do anything else.

jgmo - I'll be glad to pick up the manual; always good to be learning the right way.

I checked the float valve, and pin valves and they appear to be functional. I'm not understanding when you say check the accelerator pump plunger. I thought this is in the carb, but I don't see anything like that. Maybe I don't know what I'm looking for, or am I supposed to take the fuel pump off too?

Thank you for your advice!

I found the "Honda Marine Carburetion Manual" TM044. Is this adequate?

Yes, that's it.
As for the accelerator pump, look on the side of the carb opposite to the side that faces the engine block and has the throttle cable connection. In other words, the easiest side to get to.

There should be a little rubber "boot" or bellows about an inch or so high. The accelerator plunger goes through that bellows as that is the dust cover that keeps dirt out of the accelerator pump chamber. Never let that boot be damaged as it keeps the carb clean inside

As you twist the throttle, you should see the plunger going down and the bellows collapse. As you move the throttle back to idle, the pin should rise and the bellows extend up with it.
If niether move when the throttle is manipulated, that indicates that the accelerator pump piston is stuck in it's bore.

Thank you!

I see a little silicone or rubber boot under the throttle linkage. It is shrouded by the spring that returns the throttle to the closed position when the linkage is not attached. It does not appear to move, but I did not open it. Do I need to open it to see it function, or should I order the replacement parts before opening it?

Jimmy...

Just a reminder this engine is an 8A not and 8D like I thought it was at first.

There is no accelerator pump on this carb. And most likely, the idle mixture screw has a limit cap on it. My guess is the idle adjustment was the idle stop screw.

I agree about pulling the carb off, disassemble it and clean it.

Burn.316,

If you are turning the idle stop screw, clockwise increases idle, counterclockwise slows idle. If you turn it any way, I would recommend clockwise. You just have to be ready to turn it back, once you get the motor running, in case the idle is way too high.

Even though the carburetor looks free of goo, it is worth the time, once you have it off, to clean all the passages. It is a pretty simple carburetor.

Before you pull it again, open the carburetor drain screw and see what the fuel looks like (debris? water? etc.) also...make sure there is fuel there....squeeze the bulb and fuel should flow freely. You have to have fuel there for the engine to run. But, I guess you knew that....

If the carburetor is getting fuel and the fuel is good, the next thing that is needed when starting this engine is to make sure that the throttle butterfly is opening some when you try to start it. Advance the throttle all the way to the stop...not just to the start mark. Watch the linkage and make sure that the throttle lever on the carburetor moves some. It does not have to move a lot, but it does have to open. The throttle linkage can be a little tricky to adjust, once the motor is running, so the engine revs good in neutral, but does not overrev.

It almost sounds like it is not getting fuel. Hopefully, your new bulb/line will help with that.

Mike

Yeah Mike I was wondering if I was sending him down the primrose path......and I WAS!

Why in the world did Honda do THAT? I thought they discontinued the A when the D came out but...curses, foiled again!

Ok...no accelerator pump...GOOD! They're junk anyway....in my opinion.

But should he still get the carb manual? Or is this carb straight forward...er?

I still say try the new bulb and hose before doing anything else.

The carb is sitting on my desk. The gasket tore when I took it off, and I don't have a sheet of gasket. I get in trouble when I drink all the milk to make gaskets, so I just left it apart until I get the fuel line and can pick up a gasket tomorrow.

I cleaned the jet (sorry, my terminology probably sucks) that is accessible without taking the carb off, and the jets that go from the bowl to the body of the carburetor. I cleaned the pin that's on the float, and checked the spring inside that pin for function. That's about all I see to clean.

The screw I was turning opens and closes the butterfly. If I turn it all the way down it's open maybe 3/32" if I back it off two turns it's open maybe 1/16". Much more and it's just closed. This is probably why I was having so much trouble getting it adjusted without seeing it.

I did drain and re-fill the bowl by pumping 3 or 4 times while I was fiddling with it before I pulled the carb. The fuel looked fine coming from the drain.

The fuel is "good" in so much as I didn't buy it at the shady place (or even near the water) that jgmo used to work at, I put a fuel stabilizer in it (usually I use sea foam, but this was a different product I had) and it was known to have run the boat good at least a few times, and has not been sitting in the tank but about a week since I put it in there.

Anything else I should do to the carb while it's off? Otherwise my plan for tomorrow is fuel line, gasket, carb on, get it started, and hopefully try it on the water if it seems to fire both cylinders.

Thanks for the help guys!

And I downloaded the manual. It was free.

Awesome! You have the manual, so find your carb in it and read up! Yes there are a couple more things you should do prior to re-install and the manual will show you what those are.

No point in putting it back on without KNOWING you have it right.
You may want to pick up some low voc carb spray or brake clean with your gaskets....the compound depends on the state you're in.

I'm in California so they don't let us have ANYTHING we could put our eye out with.

But Mike warns against using carb spray that is just too powerful that you can buy in other states. He recommends brake kleen as a better alternative.

There are no specific number of turns, that I know of, for the idle screw that you are adjusting.

The adjustment comes after the motor is running to adjust the idle speed.

The idle mixture or pilot screw, as I said, are probably capped and limit any movement. If the cap is off, the initial setting is 1 3/4 turns our from lightly seated. Those typically need very little adjustment after that. If it is capped, then do not worry about it for now.

Be sure that you can shoot fluid (brakleen or wd 40) through the air jet in the front of the carburetor to be sure it shoots out the little pin hole at the rear top of the venturi. That will assure that the idle passage is clean. It should show you how to do it in the carb manual.

Mike

Jimmy,

They stopped making the 8A for a short time, but reintroduced it, calling it the "Classic 8" since it weighed a lot less than the 8D. That is why they were both available for what I remember was only about 2 years.

So, the supply store said they had my fuel line in stock. They have a universal in stock. Ordered the new fuel line, will be here Wednesday.

Took the boat out with the freshly cleaned carb and new plugs. I started about 6 times. No 1/4 power, but I did have some issues that led me to believe I am also having a fuel line problem. So, maybe fuel line is wearing out, and plugs were bad?

Should I bother to open the fuel pump?

I would not "open" it up unless you have the gaskets to put it back together.

Hopefully, the fuel line that you are getting is 5/16" inside diameter or maybe even a little smaller for this motor.....if you are reusing the fuel line connectors. If the fuel line is too large, it will not seal correctly on the connectors.

Once you get the fuel line and bulb all set up, squeezing the bulb does the same thing as the fuel pump. You just have to have someone continue to squeeze it as you test your motor.

One thing you could do with the fuel pump is, unbolt it, the with it still connected to the fuel lines, squeeze the fuel bulb until it is hard and see if you see any leaks. The pump might be leaking into one of the cylinders....flooding it. Then you are only running on one cylinder.

Mike

Thank you for the reply.

The hose I ordered is the atwood Honda assembly - I did not find an OEM hose. It lists the hose as 3/8 OD, so I would imagine the ID should be 1/4 or so. I read in the Honda manual (I believe) not to use regular hose clamps because they damage the fittings - so I didn't want to mess with the universal and replacing it without the proper clamps. I figured if I was going to replace it I'll replace the whole assembly (it's not much more expensive). If I take the old one apart and it looks good, I may investigate replacing just the bulb so that I have an extra. Also I know at some point the hose is letting gas back down the line because the line doesn't hold fuel indefinitely.

If the pump was leaking into a cylinder, would you expect that to cause other issues, like backfiring or sluggishness when accelerating?

Supposed to rain all week here, so probably a little while before I get a chance to try it on the water again.

jgmo said:

I've been doing this a few years now and on many, many occasions I've had guys say they thoroughly cleaned the carb. In more than a couple of instances they've tried 5,6, 8,10 times! You cannot tell if the carb is in condition to run the engine by looking at it. There are a couple of critical performance checks it must pass regardless of how shiny it is. That's why I constantly recommend the Honda Marine Carburetion Manual for anyone doing their own work. It's what you can't see in the carb that can trip you up. But go ahead and try the hose and bulb before you do anything else.

Click to expand...

Where do I buy a Honda Marine Carburetor Manual? And what’s the best shop manual for my ‘95 BF20?
thanks