Honda BF75 acceleration issue

[Snoopy11]

2003 Honda BF75A - idles fine, but when try to accelerate engine boggs then eventually quits. Changed fuel, fuel filter, fuel/water separator and had mechanic rebuild carb. Soaked jets and float overnight. Installed new jet set. Changed oil +filter and plugs. No change in performance issue. Not sure how to resolve issues. Any guidance is appreciated. Someone suggested to check diaphragm (hummm) adjustment.

 

[Snoopy11]

I was reading a similar post and a thermostat was mentioned as a possible culprit. Thoughts?

 

[Snoopy11]

Inspected thermostat and relief valve. Looks like thermostat was not working. Attached pic. Ordered new thermostat and gasket along with relief valve cover packing materials and O ring. Is there anything else Im forgetting or need to consider. Thank you in advance.

 

[schematic]

be sure each cylinder is contributing by killing on at a time while. Still suspect carbs, as they are not a simple clean....

 

[Snoopy11]

Thank you for the feedback. Any recommendations for detailed cleaning of the carbs? Thermostat due in this week and will replace, but symptoms sure sound like a carb issue...

 

[Rick Stephens]

You can pump fuel through the carb when you open the drain?

That carb is very simple and easy to make sure all the ports are clean. Not much to it.

Rick

 

[Snoopy11]

Thank you Rick. Yes, fuel pumps through carb while drain is open. Seems like we cleaned it, but saw a few other posts suggesting ultrasound cleaning. Didnt know if that was neccessary for this carb...

 

[Rick Stephens]

Thank you Rick. Yes, fuel pumps through carb while drain is open. Seems like we cleaned it, but saw a few other posts suggesting ultrasound cleaning. Didnt know if that was neccessary for this carb...

If you want to do the carb again, I would first get a carb kit, which is mostly just the gaskets, take it apart and use toothbrush, wire and picks with carb cleaner and make the inside spotless. Check all the ports. If you don't have an air compressor, use canned air or carb cleaner to blow through every passageway and get them squeaky clean. Check float height and get it exactly right.

The fuel pump on a Honda is just a little diaphragm pump. That diaphragm can wear out and get a crack or hole in it and it will mostly not pump any longer. Especially if the tank is much lower than the pump requiring the pump to pull the fuel up hill. Pulling it apart and inspecting it is not hard. Nor is replacing the diaphragm.

Rick

 

[Snoopy11]

If you want to do the carb again, I would first get a carb kit, which is mostly just the gaskets, take it apart and use toothbrush, wire and picks with carb cleaner and make the inside spotless. Check all the ports. If you don't have an air compressor, use canned air or carb cleaner to blow through every passageway and get them squeaky clean. Check float height and get it exactly right.

The fuel pump on a Honda is just a little diaphragm pump. That diaphragm can wear out and get a crack or hole in it and it will mostly not pump any longer. Especially if the tank is much lower than the pump requiring the pump to pull the fuel up hill. Pulling it apart and inspecting it is not hard. Nor is replacing the diaphragm.

Rick

Thanks again Rick. The fuel tank is internal on a Hewes Craft Sportsman 101. Fuel travels about 4 feet to reach carbs (~ 3ft lower). Will inpect fuel pump and diaphram for issues...

 

[Snoopy11]

Reporting back on results:
Bottom line its running and producing 5100 RPMs!!

Thermostat definitely part of the issue. Will do a separate post for a problem encountered on that job (its never ending...)

When we replaced jets in August we also replaced a missing a rubber grommet for the L-shapped air duct that channels air to carbs. On the intake end about 4" in is a screen that prevents stuff from getting sucked into carbs. There was a piece of plastic trapped there that restricted air to carbs and caused engine to bogg when accelerating or higher RPMs requiring more air . You cant see the plastic trapped unless you physically put your hand inside the intake and feel....

I appreciate everyone's comments and advice. I learn a lot during this journey

Happy Boating

 

[Rick Stephens]

Nice! Best of all possible problems. Congratulations.

RIck