Honda 40hp Tiller questions

"I just purchased a boat with

"I just purchased a boat with a 2004 40hp 4-stroke Honda tiller steer motor. It is a really clean motor that hasn't been ran much during it's life. However, it is hard to get started and then it wants to idle rough or die out. Seems to run well at higher speeds. Just from reading the forum it's probably the carbs. Could changing the spark plugs and putting in new fuel and a fuel water separator help? I'm sure it's just from sitting, just hasn't been used enough to be anything else I don't think. Even if I have to spend a little more money I still got a good deal, just want the motor to run right!

Any help would be greatly appreciated."

"Since you just purchased this

"Since you just purchased this motor, it would probably be good to change the plugs, fuel filter and water separator. Be sure to use NGK spark plugs (DR7EA). It would be good to change the motor oil and filter too. That way, you are starting out with these things as they should be.
Also, be sure not to overfill the oil. A little lower than full is best. Too much oil can contribute to hard starting and poor runability.

I would bet that at least one of your carbs have at least their idle passage plugged. More than likely it is the bottom carburator. I say that, because if you run the motor out of fuel but do not drain the carbs, the bottom carb ends up with the most fuel in it.

You could try to flush the system with fresh fuel, draining the fuel from the carbs. If you have a six gallon tank, use quick kleen or sea foam very concentrated and see if it helps.

If order to find which carb is the main problem. Run the engine on a flush (make sure the muffs are tight and you put a piece of duct tape over the intake that is above the prop under the cavitation plate)
As the engine is running, pull the spark plugs wires off the spark plugs one at a time. Use an insulated pliers. As you pull the spark plug wire, the engine should decrease in speed and maybe even stop. You should also hear the ticking of spark (this lets you know spark is good)

When you pull one and the engine does not change in speed...that is the clogged carburator.

When you clean them, do them all. If one is bad, the others are not far behind. I would recommend purchasing a Honda Shop Manual to help you through the steps of removal, etc.

Also, this motor have a lot of fuel lines and vacuum lines on the carbs. Even though the manual is helpful, it would be wise to take several pictures of the way the hoses are connected on the carbs (both front and rear). You want to be sure to put them back on correctly.

Since this motor has a fuel enrichening system, be sure to start the motor with the handle in the idle position. That is, do not advance the throttle (it will flood the engine). The motor should start and run at an rpm a little higher than idle then it should slow down to idle.

The 40HP is a real work horse and with continued routine maintenance (changing oil, gear lube, etc), it should last a really long time."

Re: "Since you just purchased this

Hi..i also have a Honda 40HP 4 stroke outboard...2001 model..I have owned it and the pontoon it is on for 5 years. It was like new when i bought it..unfortunately we havent used it nearly so much as we thought we would...maybe once a month.About a year ago i had trouble starting it and keeping it idling. I hadnt had it serviced/tuned up for 2 plus years so I had it done a year ago August. Apparently from sitting it had dirt in the gas tank, fuel lines etc. Anyway i had everything replaced including the gas tank, carbs rebuilt , hoses etcetc..Im not a mechanical type so i can describe it all. Since that time the motor has purred like a kitten. I put stabilizer in the gas tank when i fill it and we have continued to only use it about once a month . Have had no problem running it during the past year. Last week i went out to start it and while it will start when i choke it, it will not idle and wont rev up to much beyond 2000RPMs. I have no clue why it suddenly is acting up like that.I live in rural SC and it is about 50 miles to the nearest place that will work on a Honda outboard.Since i had so much done to it last year I cant understand what could be wrong now so i thought i would ask you folks for some helpful hints on how i might figure it out.As i said although im not that mechanical i am not stupid and thought maybe it is something simple i could look for if i removed the top of the engine cover. The guy who serviced/repaired my motor last year cant get to me until November and i have friends visiting next month who will want to go boating!

Anyway thank for any help you can provide or if you cant, thanks for looking at my problem. I assume there are how to instructional articles on tuning up an outboard motor somewhere. Im getting tired of fooling with this engine although i know it has a good reputation.