Honda BF150 Harder Starting

My BF150 lately has been requiring more and more cranking before she will fire up. It used to be that I would touch the key and she would fire right up but now I have to try more and more before she will start up. Once she does start she runs fine and will do so smoothly without hesitating or surging all day long. When shut down (and still warm), she will again require several attempts before restarting. Recently serviced; no fault codes, new sparkplugs, new fuel/water separator filters.

In a carburetted motor it would seem that the automatic choke is not working. Is there an equivalent to an automatic choke in the BF150? What's the purpose of the IAB (Intake Air Bypass); could the IAC (Idle Air Control) play a part as an automatic choke?

Any advice or insight would be appreciated.

The IAB only activates at 3750 rpm, so that would not be the problem. The IAC could be. Don't have a 150 manual close by, so can't give you cleaning instructions. Hopefully someone else will chirp in.

chawk_man said:

The IAB only activates at 3750 rpm, so that would not be the problem. The IAC could be. Don't have a 150 manual close by, so can't give you cleaning instructions. Hopefully someone else will chirp in.

Click to expand...

Thanks for your reply, chawk_man. Since my idle is smooth once the motor starts, I presume the IAC itself is working so that points a finger at the ECM which I'm guessing controls the IAC and would tell the IAC to act as a choke to enrich the fuel/air mixture at startup. Does that sound right? Anyone have any insight on that or any experience diagnosing this?

I would hate to sink that kind of money into a new ECM based on a guess. Again, I know little about the 150 except that it often has many of the same issues as my 225. On the 225 there are several filters and screens that are not addressed in the maintenance schedule. On the 225 there is a screen on the bottom of the HP fuel pump that can get clogged. See item 30 at:

http://www.boats.net/parts/search/H.../BF150AK0 XA/VAPOR SEPARATOR ASSY./parts.html

There is also a fuel pump filter and fuel pump filter screen that that should be cleaned or replaced. See items 9 & 10 at:

http://www.boats.net/parts/search/H...er/BF150AK0 XA/FUEL PUMP FUEL HOSE/parts.html

Also, on that same link look at the check valve, item 16. Not sure exactly what that does, but suspect if keeps fuel from back-flowing to the VST. If that check valve is not working, that could possibly be the source of your hard starting problem.

Finally see item 5, pressure regulator assembly, on the top of your fuel rail. I doubt that is the problem, since the engine runs well once started.

http://www.boats.net/parts/search/H...150AK0 XA/INTAKE MANIFOLD INJECTOR/parts.html

Thanks for your continued support chawk_man. I don't get out a often as I would like so please forgive the delay in responding, but I want to close the loop on this weird 'problem'.

As I previously reported, over the last three or so trips the BF150 became harder and harder to start, requiring more and more cranking attempts before she would fire up. The interval between trips varied from a month or so to two months or so. After starting this thread, the next time out I tried turning the ignition switch on while prepping the boat on the trailer, well before launching, thinking that maybe the electric fuel pump needed time to build up pressure. Lo and behold, she fired on the first try but missed, then quickly lit off on the second try! I had dumped an ounce of Techron/gallon into the fuel tank but don't believe that made the difference since fuel had not been flowing through the system prior to light off. Anyway, we proceeded to troll for 13 hours or so with no issues, giving the Techron injector cleaner ample time to work, then back at the wash down, the motor fired right up on the first try.

Not knowing whether the longer fuel pump on-time prior to cranking made the difference on initial light-off or the injector cleaner did the trick at the wash down, we hesitated to declare victory. Today, however, three weeks since that trip, the motor fired up as soon as the key was turned without any long lead time for the pump; all is back to how it was before the hard starting began. I'm happy to report that the problem seems to have somehow resolved itself but sorry that I cannot add any real knowledge to the collective memory here. Perhaps I had old fuel in the VST, or perhaps the injectors were lightly clogged but the only things I can say with certainty are that the motor now starts right up like it used to (I hope it stays that way) and Techron injector cleaner certainly doesn't hurt and may actually help.

Thanks again for the support and advice.

chawk_man said:

I would hate to sink that kind of money into a new ECM based on a guess. Again, I know little about the 150 except that it often has many of the same issues as my 225. On the 225 there are several filters and screens that are not addressed in the maintenance schedule. On the 225 there is a screen on the bottom of the HP fuel pump that can get clogged. See item 30 at:

http://www.boats.net/parts/search/H.../BF150AK0 XA/VAPOR SEPARATOR ASSY./parts.html

There is also a fuel pump filter and fuel pump filter screen that that should be cleaned or replaced. See items 9 & 10 at:

http://www.boats.net/parts/search/H...er/BF150AK0 XA/FUEL PUMP FUEL HOSE/parts.html

Also, on that same link look at the check valve, item 16. Not sure exactly what that does, but suspect if keeps fuel from back-flowing to the VST. If that check valve is not working, that could possibly be the source of your hard starting problem.

Finally see item 5, pressure regulator assembly, on the top of your fuel rail. I doubt that is the problem, since the engine runs well once started.

http://www.boats.net/parts/search/H...150AK0 XA/INTAKE MANIFOLD INJECTOR/parts.html

Click to expand...

Thanks for your continued support, chawk_man. I don't get out as often as I would like so please forgive the delay in responding, but I want to close the loop on this 'problem'.

After starting this thread, the next time out, I turned the ignition switch ON while prepping the boat on the trailer prior to launch, thinking that maybe the electric fuel pump needed time to build pressure up. Lo and behold, the motor fired but didn't catch on the first crank, then fired right up on the second crank. I had also dumped an ounce/gallon of Techron injector cleaner into the fuel tank but don't believe that would have had any effect on initial light-off since no fuel would flow until the motor started. Anyway, we proceeded to troll for about 13 hrs, giving the injector cleaner ample time to work, then, at the wash down the motor fired right up on the first crank.

Not knowing whether the long pump on lead time or the Techron did the trick or if it was just coincidence, we hesitated to declare victory. Today, however, some 3 weeks hence, the motor fired right up as soon as the key was turned, with no lead time on the pump! All seems back to normal but while I am happy for that (and hope it stays that way), I'm sorry that I cannot add any real knowledge to the collective memory here. I don't know if I just had old gas in the VST or if the injector cleaner did the job or what (but the cleaner certainly did not hurt).

Again, thanks for your support and advice. Happy boating to all!