Honda BF5 fouling plugs

[longshanks]

2001 Honda BF5. Used 70% as a trolling motor on a 15' aluminum skiff, which weighs around 1000lbs, in fresh water. rest of it's life is spent on a 12' jonboat, primarily for getting from point A to B, running at or near wide open.

I'm using NGK BRP5ES plugs, and getting about 4-6 hours a plug before it fouls and needs to be replaced, in order to start the engine.

I've had all kinds of problems with this engine -- not overly impressed with it. I was under the impression that a small 4-stroke OB would be very useful for me, and when I put in a new plug, it runs just great for the first couple hours, but it has proven to be extremely tempermental. Unless the plug is new, it does not idle smoothly. Last year it mysteriously lost all it's oil. And the permformance of it varies from outing to outing.

I have done a few searches on this topic, and not come up with much yet. Others I have spoken to have vouched for the reliability of this motor, but I'm having bad luck, to the point that I'm considering replacing it with a heavier four stroke twin, but I'd really like to avoid that.

carb adjustments? different plug? or scrap it? Any suggestions?

 

[P 0 P E Y E]

Re: Honda BF5 fouling plugs

Fowled plugs? With oil?

Could you have too high an oil level in the crankcase? Are the plugs loaded with oil? Could it be a function of how you store it?

how new is your gas? Is the choke working properly?

The weirdest thing I have seen a Honda 4 stoke is an exhaust leak low in the bonnet that would cause the engine to run out of oxygen and acted like fowled plugs.

An other recent find was an overheat sender shorting out, Un plug it ans see if the problem stops.

Sorry to throw a shotgun pattern of things to check. Don't give up on it before you look at the carb.

 

[longshanks]

Re: Honda BF5 fouling plugs

thanks for the response! the plug is sooty black, and I'm thinking it should be closer to tan. Runs like a top for the first few hours on a new plug, then slowly starts to bog out, run rough, and won't run above idle, then eventually stalls and won't re-start. Gas is fresh 94 octane marine gas. Oil is 3/4 level on the dipstick.

Not sure about the choke, exhaust, or overheat sender, but I'll have a look and see if they help. Because the engine works great once I put a new plug in it, I'm really thinking that my problem is related to slow fouling from the plugs, and potentially a carb adjustment of some sort...

 

[longshanks]

Re: Honda BF5 fouling plugs

I've re-checked the outboard, and run it again with a fresh plug, same thing happens after about 3-5hrs running.

NGK BPR5ES

Is anybody aware of a hotter plug that could be substituted? OR, should I be trying to adjust the carb?

 

[pvanv]

Re: Honda BF5 fouling plugs

Not sure whether the BF5 has a thermostat, but I have seen problems like this on older OMC 9.9's when the stat stuck open.

 

[hondon]

Re: Honda BF5 fouling plugs

What is your idle speed .These engines need to idle at around 1500 in gear and that can be to fast in some trolling situations.Idle set too slow will cause your exact symptoms.These engines were created largely to cater to the sailboat kicker consumer.

 

[longshanks]

Re: Honda BF5 fouling plugs

thanks for the replies. I doubt that there are any thermostat issues, or other real problems with the motor. When I stick a fresh plug in there it runs like a top. Interesting comment regarding idle speed, I am thinking my idle isn't above 100RPM, although I don't have a tach on it. As you say, when it is set slow enough for trolling, idle speed is probably lower than 1500RPMs. I will try bumping up the idle speed and trying it again.