yamaha 40hp - hesitating at open throttle + few questions

[stuey]

hi, just registered here.

ive just bought a boat with a yamaha 40hp outboard, ive been out in the boat all was ok untill i opened the throttle up.. the engine starts no problem, idles no problem and travels at a steady speed no problem, but when i open the throttle up the engine really boggs down and doset pick up speed at all (it almost cuts out) the odd time its picked up and speeded up, but most of the time its bogged out..

today i stripped and cleaned the carb out, but the problem is still there...

im not totally clued up on outboards yet so im not 100% sure on all the technical names of the parts on them!


any ideas??

 

[robert graham]

Re: yamaha 40hp - hesitating at open throttle + few questions

Check fuel system from tank pick-up tube, fittings, primer bulb, quick disconnect on front of motor, fuel filter, fuel pump. If all seems O.K. then run the motor on the water again and when it bogs down pump the primer bulb and if it picks up RPM's and runs better while you pump the bulb then problem is most likely a bad fuel pump, about $45 and easy to change. Good Luck!

 

[stuey]

Re: yamaha 40hp - hesitating at open throttle + few questions

Check fuel system from tank pick-up tube, fittings, primer bulb, quick disconnect on front of motor, fuel filter, fuel pump. If all seems O.K. then run the motor on the water again and when it bogs down pump the primer bulb and if it picks up RPM's and runs better while you pump the bulb then problem is most likely a bad fuel pump, about $45 and easy to change. Good Luck!

tried that with no joy.

the engine is about a 1990 model i think if that makes a difference?

 

[robert graham]

Re: yamaha 40hp - hesitating at open throttle + few questions

If the rest of your fuel delivery system is OK, then the carb is still dirty. If you ran some old/contaminated gas through the motor after you cleaned the carb then chances are it needs cleaning again already. Maybe install a water/fuel seperator/filter, really helps with trash/water in fuel system. Good Luck and let us know what you find on this!

 

["G"]

Re: yamaha 40hp - hesitating at open throttle + few questions

This doesn't sound like a hesitation issue but a running issue. Do these few things and I think you'll find your problem.
#1.) Do a compression check. It's a good plan to do that on every repair job.
#2.) Go through a carburetor ignition timing synchronization process and get it all in order per the specs. It's critical for proper running as well as hesitation issues.
#3.) Be sure this isn't a water issue (because of ethanol fuel) by replacing the fuel filter/water separator and blowing out the lines/fuel system. If you see any water, better go further and check the tank.

I'd be willing to bet it's ethanol problems. BTW... adding "dry heat" products is the same as adding more ethanol. Bad idea. Hint: Your engine runs on regular gas not the equivalent of E85. Yes, you may have to empty your tank and clean it. Try to get regular gas (not ethanol) when refueling. If all you can get is ethanol, keep the tank full, it will help to avoid water contamination from condensation.

Good luck and happy boating!