2001 BF40 Not Running Smoothly anymore - about 100-250'ish rpm variation

Greetings to all again - Before I have to breakdown and spend alot of money - I wanted to get all you experienced Honda folks opinion - you've all saved me in the past - maybe again today.

I have had this 2001 Honda BF40, mounted on a 13 Whaler - love the boat and motor - the motor was just serviced in September(300 hr service) before I bought it - (have the receipts, reputable dealer in Orlando). It ran great the first several times I used it - I get out about once every two weeks to use it - and it does not get ethanol fuel - 93 octane marina gas only.

Anyway - the motor just recently started to vary the rpm by about 100-250 or there about when I was idling in a canal. I listened and couldnt figure it out - only idle speed tho. (Ball is full and the racor is clear in the bowl, fuel lines appear to be relatively new also)
I had my neighbor on board and he thought it sounded like possibly air leak in the fuel line - I looked and didnt see anything -

I used the boat Sunday and noticed the rpm variation - but then when i went up to 5000 rpm - i noticed it there also - is appears to be in all the throttle range - i watch the tach and it is just barely bouncing maybe 100-200 rpm difference -

I dont want this to leave me stranded so I need to address it - and get it back to normal -
These are what I know -
Fuel is good -
Racor is clear
Fuel lines appear to be good
Bulb is good

Should i put some Sea Foam or similar in the gas tank to see if it's just a little dirt? -

thanks again for all your knowledge.

JEff

Does it still get to the full throttle rpm that it used to?

When it varies, does it jump up or down? And....does it vary quickly (like flipping on a switch) or relatively slowly?

Have you changed spark plugs? You may have a misfiring plug.

You first need to determine if it is a fuel issue or a spark issue.

Mike

Mike,

Thanks for replying to my post - I appreciate your expertise and sharing the knowledge you have.

The motor seems to drop down about 100-250 rpms - about every 3-6 seconds -

i was going to change the Racor today and probably go ahead and do spark plugs and the fuel line - this all started after about a 1 hour canal cruise at idle speed - so i am thinkin maybe the plugs got fouled -- so I will clean them and see how it goes - if it still does it - i'll replace them - and if it continues - i think i will go ahead and do new fuel lines -

starting with the cheap things first.......

If changing the plugs does not help, bypass all the external filters etc and take them out of the picture. If the problem goes away, then you know where to look.

My guess is the plugs. Be sure to use NGK DR7EA plugs. Not Champion or some other brand.

Mike

Thanks for the advice - ran out of time yesterday on working on it - got new fuel line on - new racor - the spark plugs looked pretty good - took one down the dealer where i buy parts - and he said it looked great - no issue........

had a problem finding a new 5/16' in fuel line and bulb - everyone has the 3/8's line......i'm curious if i should upgrade the one i've got to the 3/8's.......mine on the motor connector has the round lock instead of the rectangular locking mechanism - is it difficult to replace the male connector on the engine? - never really looked at it to be honest...

The Honda fuel fittings are too small for 3/8" line. You can probably use 3/8" from the fuel tank to the Racor, if you use the 3/8" barbed fittings. Unless you use 3/8 to 5/16 adapters, you will have to use 5/16 to the engine connector.

If you try to use 3/8" hose on 5/16" fitting, most likely, you will be sucking air.

I would make up my own.....Find yourself a an Evinrude Dealer and get a 5/16 bulb http://shop.evinrude.com/product/553944/5008605/_/EPA_Primer_Bulb_Assembly_516%22_-_5008605
Not cheap, but the best out there. They will probably also sell the newer EPA compliant hose. Get the lengths to fit your application and put the Honda fittings on the end and you will be good to go for quite a while. Most other bulbs and line are crap and will fail in a few months to a year or so.

It is easy to change out the fitting on the engine, if that is a problem. There is a kit that has a fitting with rectangular lock and its matching hose fitting. Part number 04104-ZW9-000. Generally, you can tell there is a problem by squeezing the fuel bulb and checking for a leak when the bulb gets hard. If no leak, it is probably fine.

Mike

Mike,

I got to work on it a bit yesterday -- new lines, new bulb, new plugs - seems to run fine - there is just a slight variation to the rpms - maybe less than 50 - I hear it - but dont see it in the gauge - I dont know if that is normal or not - but it certainly seems to run better than it did before the new plugs and line -
if i am idling - no wake zone, I can hear where it seems to sometimes - miss.....not really smooth like my honda 150 is - so i dont know what the deal is.....agitates me to hear it tho...

thanks for the evinrude tip - i'll order one of those for next replacement....

jeff

Hondadude - I have seen this up and down idle on a few Hondas now and I was wondering if it could be anything to do with the O2 sensors? We just had one replaced on a BF175 and it seemed to smooth out the 'hunting' at idle speeds. Not sure though whether this was a direct result of coincidence.

Does a 2001 bf40 have an 02 sensor?

The 2001 40 HP is carbureted and has no o2 sensor.

I agree, the 150 does idle much smoother. One thing that should be done every so often to the 40 is to vacuum balance the carburetors. That does help it to smooth out more at an idle.

Mike

Mike,

Thanks again for your help - sometimes, it's just really good to hear from someone that confirms what you think you should do to fix an issue - I by know means am a mechanic - just trying to avoid paying 100.00 an hour for something I can do myself - with limited skills.

thanks

If you don't have one already, invest in a Helm Shop Manual. It will save you a lot of money over time.