Honda accelration problems on carbureted models

[o/b tech]

Has anyone experienced acceleration issues when the throttle is opened quickly. The carbs have been completely done. Float height set and all jets clean. The motor has been run-up in test tank and the lync and sync was done with the vacuumate hooked up to the motor. The idle speed is correct and the mixture screws are set to spec. Have been working on two honda outboards. One is a 1997 45hp three cylinder carbureted and the other is a 2003 75hp four cylinder carbureted. Both have the same issue. Will accelerate slowly and may hesitate but when the throttle is snapped they will stall. The accelerator pump is also set to spec. Will order new check valves and see if it improves.

Any info would be great.

 

[MattFL]

Re: Honda accelration problems on carbureted models

It is a lean condition. The smaller motor doesn't have an accelerator pump does it? Anyway, do they have this issue at full temp, or only when cold? Mine will cut out a tad when you whack it open and its not hot yet, but once hot it doesn't do it. There is another thread about this already if you search.

 

[o/b tech]

Re: Honda accelration problems on carbureted models

Yes both motors have an accelerator dashpot. They both bog and want to stall whether they are warm or cold. I haven't found any concrete answers yet. Still looking though.

Thanks.

 

[Sea Rider]

Re: Honda accelration problems on carbureted models

Probably both have already worn, dried, cracked head gaskets related issues, Both lets small water droplets inside combustion chambers and misses, specially when giving medium to full wot throttle at any engine temperature. One is a 16, the other a 10 year oldie. Head gaskets doesn't last that long, worst if constatnt working on seawater.-

Happy Boating

 

[MattFL]

Re: Honda accelration problems on carbureted models

I disagree about the head gaskets, properly maintained motors go for years and years without replacing a head gasket. Carbureted Honda motors are typically jetted on the lean side and what you're reporting is exactly what a lean condition behaves like. On motors with an accelerator pump, it is the job of the accelerator pump to dump a bunch of gas in when the throttle is opened quickly to prevent the bog caused by the lean condition. I suspect an issue related to the accelerator pumps. If you remove the airbox and look into the carbs and have a buddy open the throttle (with the motor off) you should see a momentary stream of gas from the accelerator pumps spraying back into the intake manifold. If you don't, then that's your problem. That said; I've got a 1999 Honda 50HP (3 cylinder carbureted) that does not have an accelerator pump, so it's interesting that your two motors do have them, especially the newer motor since accelerator pumps are not good for emissions. If your local gas is high in ethanol then you might want to try to find some non-ethanol gas to give a try. Ethanol burns fine, but it requires more ethanol than gas to avoid being lean (the motor needs to be adjusted to run richer) so if your gas has a lot of ethanol then that can also contribute. The last thing I can think of is very worn spark plugs with too much gap can also cause behavior that is similar to a lean condition.

 

[Sea Rider]

Re: Honda accelration problems on carbureted models

Sorry to disagree too :

"Probably" means a asssumption, have not stated head gaskets are kaput already, you can't "maintain" head gaskets, are sealed...

1-Poster hasn't specified if both engines were run or are being run on saltwaterr basis. Head gaskets are not eternal, if engine is poorly rinsed after each outing or not rinsed at all, salt will end eating, distorting crankcase and head mating metal surfaces, when engine is warm this condition will lead small water droplets to pass into combustion chamber and miss badly when giving throttle, worst at 3/4 to wot. Besides nobody re torques heads to check if still torqued to factory specs.

2-Throttle is snapped is a vague definition, on carbed engines you can play with idle adjustments all you want, engine will miss just at idle if not correctly set, on higher rpm just passing idle, engine should not miss as all as jets on carbs are fixed and non adjustable. Ethanol is not the cause, as others having same engines should be experimenting same issue.

3-If plugs happen to be original oldies, buy a new set, gap well to specs. You could also have fuel tank and fuel line related issues, including electrical issues. Will need to troubleshoot through fully both engines to find the cause.-

Happy Boating