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Honda BF 135A

J

joe.gwiz

New member
I have a 2004 BF 135A. Engine alarm sounded. Mehanic said code indicated a defective MAP sensor which was replaced. Alarm sounded again after running less than 10 minutes. Code indicated bad LAF Sensor which was replaced. Alarm sounded again during short sea trial. Mechanic counsulted Honda (again) replaced the EMC controll unit. Alarm still sounds. Mechanic checked and clead all pins checked continuity, grounds etc. Hooked up portable ignition box to eliminate harness issues. I had the mechanic disconect the alarm. Engine was difficult to start but ran well for 2 hours. Now it runs rough and can only run at idle or it will stall.

Do I cut my losses at this point?
 
I've never worked on a 135 Honda but I will offer you this:

My experience with automotive fuel injected systems is that, when multiple codes are logged, it can often be due to poor ground connections.

An explanation of that is that if a signal encounters a poor ground and then finds a different path in the system via a sensor or other component, it can "scramble" the signal and cause the ECU to be "confused".

Marine electrics are subject to way more corrosion issues than in most cars so periodic cleaning is often necessary for power and ground points in an outboard's main connections.

In addition to that, it's long been known that alternating current "riding" on the direct current signal in a 12 volt system can also be disruptive to the operation of the ECU. This is due to diodes going bad in the alternator and is known as "ac current ripple".

Ac ripple can be measured at the battery terminals using a quality digital multimeter set on the millivolts AC scale.

The battery must be fully charged and in good condition so as not to get skewed results.

A reading of more than 50 ac millivolts @1500rpm is usually a cause for concern although some systems allow 100 millivolts.

Good luck.
 
Find a competent mechanic, there's more to diagnosis than looking at fault codes. He needs to read actual values and see what is causing the issue, it isn't hard or complicated if you know what you're doing. The first go to before any efi issues are looked at is to make sure engine is mechanically good ie compression, then fuel pressure and a check for a possible leaking or faulty injector which can be the cause of O2 sensor alarm.
 
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