Honda BF75a - Intermittent Power Issue

I recently purchased an ?06 BF75A that supposedly has 100 hours on it. It was professionally rigged and ran flawlessly when first used; full, smooth power. Then she started talking back. The engine periodically enters a phase where it idles rough (kind of a random chugging mixed with the regular idle sound). The engine just gets my boat on plane when in this state and will not rev above 4600 rpm. The difference in power and sound night and day. Then at a random moment the world is right again and she purrs like a kitten, resumes producing full power up to 5800 rpm. I did several simple things to try to alleviate the problem; changed and gapped plugs to spec, added a canister type fuel filter, ran 1/2 way through a full tank of clean non-E85 fuel and checked the linkage. Betty returned to her cheating ways after thanking me for the makeover and drinks with one uneventful trip. I thought that the condition maybe associated with rough seas since it occurred several times in a medium chop. I went through the wiring harness looking for loose or suspect terminations during one of her moods only to be greeted with the same cold shoulder when I romanced her into the lake. I have decided not to run her again except to test until communicating with an online psychiatrist. I am mechanically inclined and am capable of working on the motor?s externals. Any thoughts from a mechanic or person who has had a similar problem with a Honda BF75a or 90a carbureted four stroke? Many thanks to the person who can help me sleep in my own bed again.

Re: Honda BF75a - Intermittent Power Issue

with that much rpm loss and with it coming and going like that. I would have to say it would be an ignition coil working only sometimes

Re: Honda BF75a - Intermittent Power Issue

Ignition problems with this engines are extremely rare.Keep in mind that you have a carb for each cylinder and one tiny piece of crap in any one of those carbs could cause your exact symptoms.

Re: Honda BF75a - Intermittent Power Issue

Might the bits of trash eventually pass through or could this be a single impurity rattling around and periodically causing a carb problem? Would it be of any use to fill and drain all carbs several times? I ordered the top and bottom ignition units to swap in the event that they are faulty. Could I have caused any damage running the engine with either condition? I need to attempt troubleshooting where the boat is because of the plus three hour haul to a reputable mechanic. Many thanks for the suggestions. I plan on working on the engine over the weekend and will report any progress.

Re: Honda BF75a - Intermittent Power Issue

Make sure that the fuel filters are absolutely clean. You do have a water separator filter? Make sure to drain the fuel from the carbs after each use. You might try some "Seafoam" in the fuel, available from Walmart.

Re: Honda BF75a - Intermittent Power Issue

All filters are new as is the in-line water separator. Drained all carbs repeatedly per an older post?s recommendation. Ran the engine without an issue for four hours this weekend. Will wait to see how the engine performs over time before replacing the ignition units so I will better know what the problem is or was. Thanks again to everyone. I will keep this thread going if the problem reoccurs.

Re: Honda BF75a - Intermittent Power Issue

Wow, it's sure nice to hear someone is having "our" problem. Ours is a '06 BF90 (carbed) and we've been experiencing the exact same symptoms you describe since we purchased our boat about this time last year. Our 90 also came to us with about 100 hours and we've almost doubled that now. Unfortunately, I'm not very mechanically inclined, so after many trips to the mechanics (3 hours RT to the reputable one for us also), we've been through the entire fuel system, cleaned carbs twice, and replaced both fuel pumps per Honda Factory's recommendation. After many trial runs after many trips to the mechanics we are still scratching our heads. It's such a random, intermittent, and randomly intermittent thing that at this point it's a toss-up as to which of us is going to require an appointment with Dr. Phil first. Sometimes she "talks back" every 5 minutes and sometimes much longer, one time being more than 30 hours between the hiccups (which naturally was right after the wife and I called the thing "fixed" and high-fived). aaarrrggg! On our last trip out we discovered that the symptoms are exactly the same as pulling the choke lever under full RPM. The engine starts to cut out (never ever dies) and the cabin fills with gasoline fumes. No, the choke solenoid is not acting up, we disconnected that. I went as far as balancing on the transom and pulling the engine cover off in 1 foot chop in order to verify that the choke wasn't somehow actuating.

Great forum here. If you discover anything at all that seems to help your situation, please let us know.

Re: Honda BF75a - Intermittent Power Issue

My issue was likely bad fuel. I installed an in-line water separator. The motor has run flawlessly since my last post. Good luck to you.