BF225 intermittent stuttering and shaking at idle

Hi,

watching video could tell more.
https://www.youtube.com/watch?v=Q6x7kaIH9Ig


I recently brought 2010 Honda BF225 AAK and tested on nearby river before out to ocean for salmon fishing.

When I test it at home, it only can started at second time. Even thought primed fuel before engine start, first time always failed. Though it always fired at second try. I've heard this motor was used by coastal guard with about 1000 hours and second owner used it about 200 hours.

On the river, the motor was surging at about 3-4000rpm and couldn't get plane and there was gas smell. tried few times and got same results. check the prime bulb empty and pumped until hard. From this point the motor worked great.

After return home, I tested again and got the same result as the video. So I changed:

Engine Oil and filter
Prime bulb with fuel line (west marine brand)
Low pressure fuel filter with o ring
High pressure fuel filter with o ring
Water separator filter (Racor type mounted on boat gas tank)

After changed above, same result and took the video to ask this forum.

Any advise will be appreciated.

Gas smell is not good! I assume that the gas smell is coming from under the engine cover - is that correct?

Find out where it's coming from. You could be sucking air into the fuel. Turn on the key switch for 2-3 seconds to activate the fuel pump to build pressure. First place to check is that new O ring you installed with the new HP fuel filter. They can easily get pinched. Check the cover to the HP fuel pump. Check the fuel lines to & from the VST. Check the fuel lines going into and out of the LP fuel pump. Check the fuel lines to the LP fuel filter and the on board fuel/water separator. Check the fuel line to the fuel pressure regulator.

Drain the VST - Procedure is in the owners manual. Test again.

Adjust the valves. Test again.

Test fuel pressure - it should be between 41 and 48 psi at idle with vacuum tube removed from fuel pressure regulator and clamped. (You will need a 6 mm adapter for your fuel pressure gauge.) If fuel pressure is out of spec, remove and clean fuel pressure regulator. Test again.

BTW - I find it hard to believe USCG put only 1000 hours on a 2010 BF 225. Usually they run them until they give out - 5,000 to 6,000 hours or more. If there is a Honda dealer nearby, have them hook up Dr. H and get the real number of hours on that engine.

Thank you for your advice chawk,

The gas smell was come from the propella area only when the shaking is occured and when couldn't get the plane with high rpm.

I have re-cramped the fuel hose from gas tank to low pressure filter when first time inspect the motor because I found a gas leak at the end of the fuel hose to low pressure filter when I primed the bulb.

Tried to drain VST. Unfortunately the drain screw looked badly corroded and could find the gap to apply a flat screw driver to turn it.

I tested the motor right posted this forum, and the shaking symptom occured once only when cold start compared last time that symptom occurs repeatedly every few minutes. Tested it today morning and occured one time after 1-2 minutes of cold start and idles fine after that for more than 30 minutes.

I just believed the seller's information when the engine sound is pretty smooth except when the rattling compared to my last 7 years old, 200 hours Mercury Optimax 75HP.

Thought the next thing to try should be replacing the low pressure pump since the seller mentioned he recently had to prime more frequently and I have resolved the "unable to get plane" by prime the bulb. Am I on the right track?

OK. Are you saying now that the engine is running fine except for just at startup?

Going back to your video, when the engine starts shaking it sounds like you are losing rpm's. Do you have a tachometer installed? If so, what is the reading when the engine is shaking? If much under 500 rpm, it's going to shake, regardless of what shape it's in.

Did you replace the entire fuel line from the primer bulb? If so, after installation did you check for kinks, especially at that big black grommet?

The only way I know of that a gas smell can get to the prop area is 1) it's leaking down from the engine compartment, or 2) one or more of your cylinders are not firing and you are expelling gas vapors through the exhaust. Could you have residual gas sitting in the bottom of the engine compartment from that fuel line split at the low pressure filter?

If not, pull your spark plugs and inspect. All electrodes should have a milk chocolate brown coating. If all are dark and sooty, you are running too rich. That can be caused by several things - 1) thermostats stuck upon so you are running too cool, 2) HO2 sensor failure, 3) fuel pressure out of spec are the main reasons. If one or two plugs are shiny clean or very sooty black, they are likely not firing or misfiring, so replace. BTW all your plugs should be NGK IZFR6F11 only. Test the coils mated to any of the shiny plug(s). The coils seldom go bad unless they are cracked or have a bad connection.

If you can't get that VST drain screw open, remove the upper starboard cowling so you can get to it easily. Carefully re-open the screw slot with a dremel tool. Soak the screw in PB Blaster or similar penetrating oil. Then, with the screwdriver firmly in the slot, tap, tap, tap...You may have to repeat that several times over a day or two -- soak and tap, soak and tap. If it still won't come loose, you are going to need to remove the VST and very carefully drill it out.

Update from last post.
Checked the engine at nearby dealer shop and got HO2 sensor failure. Mechanic cleared the code advised to use the motor 3-4 sea trips and bring it back to the shop if the symptom returns. After O2 failure code cleared, the shaking and stuttering is gone for few days. And the symptom is returned at 4 days after the code cleared. So I replaced O2 sensor and spark plugs and tested the stuttering was gone so bring the boat to try on bay ocean.

While I was testing the motor idle to full throttle on the water, I notified that long alarm was on when RPM is about 4000 and got off when RPM is exceed 5000. When alarm was activated around 4000rpm, it was off if I lower the rpm or higher the rpm. There was no sign of any performance decrease or malfunction. Just a alarm. Even I did it for full throttle at over 6000rpm for over several minutes without alarm. Then when I decrease the rpm and it was reached about 5000rpm, the alarm was on again and off when the rpm was below 4000. But the alarm was not always activated, sometimes no alram when the rpm hit 4000-5000 range.

I replaced aftermarket O2 sensor and didn't cleared the error code after installation. Would it be the culprit?

In other word, the constant long alram only activated when rpm range 4000-5000 without any other simptom. The light on tacometer only have green light is on and no other light is on during the alarm activated.

I researched this forum throughfully but couldn't find the same simptom. Please advise.

You need to get someone to use Honda diagnostics on a water test to see what is happening.Usually a continuous beep is associated with guardian where the ECU pulls the engine RPM down to idle or even full shut down.Your idle issue could be solved by checking valve clearances, when were they last checked, do you have any service history? You also don't mention fuel pressure, has that been checked? As far as O2 sensor fault clearing is concerned, no, it will not affect the engine, it will only store the fault in the fault history, it only affects the engine if the fault is current and active.