Honda BF15 2003 Idle and Prop problems

Hello,

I'm from the Netherlands and just bough a 15 hp Honda outboard. The engine has been sitting for about 3 years. I've been running the engine nog for about 3 trips, 7 hours. Yesterday the engine performed bad ad idle, when started cold the engine idles, but after one hour the engine became a bit jerky and won't idle anymore. Oil, sparks etc has been changed 3 years ago, and the engine did not run since now. What is the best thing to do, clean out the carb? Or is it a known problem.

Second thing, at WOT (full throttle) you can hear a slight rattle from the engine. When i lower the RPM just a little bit, it disappears and everything sounds fresh.

Third thing, at the end of the trip yesterday the rpms start to clime but not the speed. Is this due to a loose prop? And what can i do about it?

Fourth thing, when i yesterday get the cover off the engine, i was wondering if it needs an air filter housing. It doesn't have this: 17390-ZY1-000

Fifth thing, how can i adjust the carb. On the side of it is one screw which is turned 3,5 times from totally in. Is this the idle screw?

Thanks for the help ik advance.

Hi,
The '03 15hp Honda is a great outboard. Sounds like you have a few wrinkles to straighten out though on this one.

It is pretty likely that the carb could use a good cleaning. These little carbs are fairly "finicky" about fuel quality and maintenance and can be difficult to get cleaned properly if you've never done it. I recommend that you have the HONDA MARINE CARBURETION MANUAL TM044 before attempting to service your carb. I have a book version that I purchased on Amazon but I have been told the manual can be downloaded for free off of the internet. Sorry but I can't tell you how to do that. I just don't have that information.

QUESTION: Is your outboard a pull start only or electric and pull start?

Anyway, getting back to the carb...
The carburetor needs to completely drained of fuel if the outboard is not going to be used for 2 weeks or more. I have essentially the same one (20hp) and I drain mine pretty much anytime I park it for more than a day or two. This prevents evaporation in the float chamber that can leave minerals and deposits from forming.

One other thing that needs periodic attention is the "fuel chamber". The fuel chamber (item #2 in the parts page link below) acts as a water separator and, therefore, should be taken off and drained every 30 to 45 days. Or, anytime you experience starting or idling problems.

https://www.boats.net/catalog/honda/outboard-by-hp-serial-range/15hp/bf15d3-lrta-2003/fuel-pump-1

If you drain the fuel chamber and the outboard runs ok again, you may not need to clean the carburetor at this time.

The rattle noise could be one of several things and may require some detective work. You can use an old broom handle as a sort of stethoscope to try to isolate the area the noise is coming from. If it's coming from under the hood then take it off and SECURE IT. Run the outboard and use the broom handle or stick to try and pinpoint where the noise is loudest. Sometimes it's the pull start mechanism but it could be any number of things. When you think you've found the "spot", look for loose or missing fasteners or possibly broken items in that area. If the noise is at the top of the outboard, you can remove the pull starter and run the outboard with it off. If the noise isn't there anymore then it's likely the spring in the pull start assembly and that could be considered normal. If you still hear the noise, it may be coming from under the flywheel. That would need to come off for inspection of magneto and charge coils as well as the crankshaft retainer nut and thrust washer. BE VERY CAREFUL RUNNING THE OUTBOARD WITH THE FLYWHEEL EXPOSED!

Your prop may indeed have a bad hub. If you put the outboard in forward or reverse and can turn the prop by hand then the hub has failed and you will need a new propeller. Another way to check it is to put a mark on the inner portion and a matching mark on the outer portion of the hub and then drive the boat. If the two marks are no longer aligned when you check it again then the hub is failed.
CAUTION: Make sure ignition is off and kill lanyard and key is pulled prior to working with the prop.
Also, make SURE that you are slowly turning the propeller while shifting the transmission with the engine off. NEVER force the transmission into gear! You can damage your shifting linkage by forcing the transmission or shifting when the prop isn't turning.

The housing you are referring to is called the muffler. It contains no filter. There is no air filter. The muffler is there primarily to reduce engine running noise. Inside the muffler is a backfire or spark arrestor screen. I can't say, one way or another, if it's harmful to the engine to run it with no muffler but I will say that I would replace it if it were mine. One reason is that the crankcase vents back into the intake via a hose connected to a passage in the muffler housing. Running without that hooked up and directing crankcase gasses back into the intake will eventually lead to an oily mess throughout the engine compartment.

I need to go.
I, or someone else, will address your carb adjustment question a bit later.

Thank you very much for your nice answer. I've good news about the idle problem. I just took the carb off the engine, and through the idle jet was nog visible light. I blow the thing with some brake cleaner on white paper, and there was en tiny bit of dust in the jet. Now the engine runs normal at idle again.

I'm glad to hear that the BF15 is normally a good engine. I will take a look at the hub tomorrow.

Hi,

I will say that you probably got very lucky on the carb. They usually are not that "cooperative". You should use the good fortune to take the time to try and find a copy of the carburetion manual.

Yes, I like to say that the Honda twin cylinder outboards are "bulletproof" if a fairly minimal degree of good maintenance is observed. But, the carburetor will not fair well on anything but clean, quality, gasoline and frequent drainage.

Let us know what else you find and,

Welcome to the Forum.