Yamaha 40-HP Four-cycle: Runs Poorly, No Alarms

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Author Topic:   Yamaha 40-HP Four-cycle: Runs Poorly, No Alarms

mojack posted 08-10-2008 05:25 PM ET (US)
Hi. I just bought a used 1999 Yamaha 40-HP four-cycle outboard and put it on the back of my SPORT 13. On the first trip out, it was a short ride from the ramp to the wharf and it did fine, other than some porpoising. I put a foil on the [anti-ventilation] plate. The motor wouldn't idle and sounded rough at higher RPM, so I had the carburetors removed, cleaned, and reinstalled. She purred like dream.
I went to pull the kids on the tube yesterday. When I first took off [the 1999 Yamaha 40-HP four-cycle outboard] bogged down. I thought maybe it was just cold, so I let it warm up a bit. After a few minutes [the 1999 Yamaha 40-HP four-cycle outboard] kicked in and I was able to pull them for a few minutes and then it would bog down again. A few times it helped if I squeezed the [fuel primer bulb] really hard, but even that wasn't fool proof.
I was able to limp back to the ramp today at about 20% of full throttle. Anything more and [the 1999 Yamaha 40-HP four-cycle outboard] would bog down, but would hold the 20% fine. Fresh gas, new platic fuel tank, newly cleaned carburetors, full bubble on the fuel line, line not kinked anywhere--what else could it be?
I also thought these motors came with audible alarms for engine problems and that when the key is turned in the ON position, the remote control would beep to let you know it was working. The remote control is a 703 that I bought as "old stock." There are two smaller wiring harnesses coming out of the back of the remote in addition to the main harness. Should these be plugged into something else on the motor for the alarms to work?
Any and all advice appreciated!!
~Derek

Casco Bay Outrage posted 08-10-2008 06:41 PM ET (US)
Bogging down really sounds like a fuel problem.
Often carbs need several cleanings to get them really clean. It is possible the first cleaning did a great job but your short run loosened some other crud and now it is clogged.
Check the fuel filter in the engine.
Are you using straight gasoline or gasoline blended with ethanol?
How are the plugs? Remove inspect and if old or with deposits, install new ones.
My engine (F115, 4 stroke) experienced this same symptom this spring. Fuel system needed cleaning.
mojack posted 08-10-2008 07:04 PM ET (US)
Hi Casco Bay Outrage,
I always run 93 octane. It's more expensive but I find I get better gas mileage and it is supposed to be better for the fuel system (car and boat). I noticed before I got the boat in the water (running it at home) that the fuel filter under the cowling wasn't full. I could actually see it filling up at one point. I should probably replace the plugs also along with the foot grease. So you think I possibly might have to have the carbs removed and cleaned again??
Thanks!
~D
mojack posted 08-10-2008 07:58 PM ET (US)
I found the fuel pump and the two "out" lines. I started up the motor and removed the top one and then the bottom one and revved up the motor a bit to see if there was any change in the stream. What I observed from both "out" ports was an intermittent but rhytmic squirt not a steady stream and both my wife and I observed the flow actually decrease by about 1/3rd when I revved the motor up. Does this sound like a bad diaphragm or entire fuel pump? Also, what about the "chirp" for the motor alarm that I hear when a lot of guys turn the key on?
Thanks!
~D
mojack posted 08-12-2008 07:54 AM ET (US)
I did some more investigating on the alarm and found that the "horn" worked when direct wired. I also turned the key on and put a screwdriver into the connector on top of the temp sensor on the block and tried to ground it out on the motor and the horn didn't alarm. I remember when I got the motor there was an electrical connector that was disconnected, so happens it has a pink wire which is the same color as the wire going to the temp sensor on the block. I had reconnected it because it looked like it went together. Does this motor have some kind of protection feature that will only allow the motor to run at a certain low rpm if something isn't working correctly??
Thanks!!!
Derek
jimh posted 08-12-2008 09:10 AM ET (US)
In the owner's manual for most Yamaha outboard motors there is a small but comprehensive electrical diagram that shows the configuration of the motor's circuitry. This should show you how to connect the gauges and instruments to the motor.
mojack posted 08-12-2008 09:24 AM ET (US)
Thanks Jim,
I have no external guages for this motor and the alarm circuitry should be incorporated in the 10 pin wiring harness. I just didn't want to start replacing parts (i.e. fuel pump, filter, temp sensor, etc) if it is just a matter of something wrong with a sensor. I've only had this motor a little over a week and have not received the yamaha repair/service manual as I didn't want the Seloc type manual but the mechanic's manual. I tend to think that there is some correlation between the bogging down and the sensor connector being disconnected but wanted to make sure.
Thanks!
~D

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Author	Topic: Yamaha 40-HP Four-cycle: Runs Poorly, No Alarms
mojack	posted 08-10-2008 05:25 PM ET (US) Hi. I just bought a used 1999 Yamaha 40-HP four-cycle outboard and put it on the back of my SPORT 13. On the first trip out, it was a short ride from the ramp to the wharf and it did fine, other than some porpoising. I put a foil on the [anti-ventilation] plate. The motor wouldn't idle and sounded rough at higher RPM, so I had the carburetors removed, cleaned, and reinstalled. She purred like dream. I went to pull the kids on the tube yesterday. When I first took off [the 1999 Yamaha 40-HP four-cycle outboard] bogged down. I thought maybe it was just cold, so I let it warm up a bit. After a few minutes [the 1999 Yamaha 40-HP four-cycle outboard] kicked in and I was able to pull them for a few minutes and then it would bog down again. A few times it helped if I squeezed the [fuel primer bulb] really hard, but even that wasn't fool proof. I was able to limp back to the ramp today at about 20% of full throttle. Anything more and [the 1999 Yamaha 40-HP four-cycle outboard] would bog down, but would hold the 20% fine. Fresh gas, new platic fuel tank, newly cleaned carburetors, full bubble on the fuel line, line not kinked anywhere--what else could it be? I also thought these motors came with audible alarms for engine problems and that when the key is turned in the ON position, the remote control would beep to let you know it was working. The remote control is a 703 that I bought as "old stock." There are two smaller wiring harnesses coming out of the back of the remote in addition to the main harness. Should these be plugged into something else on the motor for the alarms to work? Any and all advice appreciated!! ~Derek
Casco Bay Outrage	posted 08-10-2008 06:41 PM ET (US) Bogging down really sounds like a fuel problem. Often carbs need several cleanings to get them really clean. It is possible the first cleaning did a great job but your short run loosened some other crud and now it is clogged. Check the fuel filter in the engine. Are you using straight gasoline or gasoline blended with ethanol? How are the plugs? Remove inspect and if old or with deposits, install new ones. My engine (F115, 4 stroke) experienced this same symptom this spring. Fuel system needed cleaning.
mojack	posted 08-10-2008 07:04 PM ET (US) Hi Casco Bay Outrage, I always run 93 octane. It's more expensive but I find I get better gas mileage and it is supposed to be better for the fuel system (car and boat). I noticed before I got the boat in the water (running it at home) that the fuel filter under the cowling wasn't full. I could actually see it filling up at one point. I should probably replace the plugs also along with the foot grease. So you think I possibly might have to have the carbs removed and cleaned again?? Thanks! ~D
mojack	posted 08-10-2008 07:58 PM ET (US) I found the fuel pump and the two "out" lines. I started up the motor and removed the top one and then the bottom one and revved up the motor a bit to see if there was any change in the stream. What I observed from both "out" ports was an intermittent but rhytmic squirt not a steady stream and both my wife and I observed the flow actually decrease by about 1/3rd when I revved the motor up. Does this sound like a bad diaphragm or entire fuel pump? Also, what about the "chirp" for the motor alarm that I hear when a lot of guys turn the key on? Thanks! ~D
mojack	posted 08-12-2008 07:54 AM ET (US) I did some more investigating on the alarm and found that the "horn" worked when direct wired. I also turned the key on and put a screwdriver into the connector on top of the temp sensor on the block and tried to ground it out on the motor and the horn didn't alarm. I remember when I got the motor there was an electrical connector that was disconnected, so happens it has a pink wire which is the same color as the wire going to the temp sensor on the block. I had reconnected it because it looked like it went together. Does this motor have some kind of protection feature that will only allow the motor to run at a certain low rpm if something isn't working correctly?? Thanks!!! Derek
jimh	posted 08-12-2008 09:10 AM ET (US) In the owner's manual for most Yamaha outboard motors there is a small but comprehensive electrical diagram that shows the configuration of the motor's circuitry. This should show you how to connect the gauges and instruments to the motor.
mojack	posted 08-12-2008 09:24 AM ET (US) Thanks Jim, I have no external guages for this motor and the alarm circuitry should be incorporated in the 10 pin wiring harness. I just didn't want to start replacing parts (i.e. fuel pump, filter, temp sensor, etc) if it is just a matter of something wrong with a sensor. I've only had this motor a little over a week and have not received the yamaha repair/service manual as I didn't want the Seloc type manual but the mechanic's manual. I tend to think that there is some correlation between the bogging down and the sensor connector being disconnected but wanted to make sure. Thanks! ~D