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Author Topic:   Yamaha 90-HP Two-cycle Outboard Lacks Power

jstarzy posted 06-04-2012 11:10 PM ET (US)
I anticipated a nice ride from Morgan NJ to the Navesink in Rumson in the Montauk, [but the Yamaha 90-HP two-cycle outboard engine] acted up. [The Yamaha 90-HP two-cycle engine seems to have] no power over 3,000-RPM. The throttle movement from 3/4 to full did nothing under load, but [the engine speed response to throttle movement] was normal in neutral for a short spurt. After playing around for 30 minutes in Raritan Bay, I returned back to Morgan. I will take the boat out of the water, examine it again at the end of the week, and head to S&S for repair.
I would really appreciate thoughts on what the problem could be. Here are some symptoms and some observations:
--no increase of RPM over about 3,200 under load.
--full increase in RPM under no load
--throttle above 3/4 under load does nothing
--no alarm from the oil tank safety limiter though I did not remember to look at the gauge
--swapped fuel tanks and ran a direct line without the Racor filter to a tank with fresh gas, no improvement
--idle in gear seemed lower than normal at about 500-RPM instead of the normal 700-RPM
--engine overall sounded quiter and a bit anemic, even on muffs in the driveway prior to launch.
The engine is a 2003 model year two-cycle with just under 110 hours and it is not abused. I just did a water pump [service] a few weeks ago. It went smoothly, though coincidental this problem should happen now. Aside from the trim cap seal the engine has been trouble free, though when running normally. The engine does not seem to get the 1989 Montauk with 20 gallons of gas and me at 170-lbs over about 36-MPH. I read others with the same set up get 40 to 44-MPH.
With this current problem, the engine almost seems like it is running on two-cylinders instead of three. I did not have a chance to look at the plugs yet.
[I think the causes may be] clogged high speed jets, a bad coil, an ECU, or timing. [I hope the repair] is minor. Thanks for any help--Jim.
Tom W Clark posted 06-04-2012 11:51 PM ET (US)

quote:
...the engine Almost seems like it is running on two cylinders...
Yes, it does, doesn't it? Since these Yamaha thee cylinder motor were rather notorious for loose spark plug boots, why not see if that's the problem? Always start with the simple and obvious things first, no matter how unlikely you think they may be.

quote:
Full increase in RPMs under no load
Uh, yeah. That's because there is no load on the motor!
Why do so many folks think that revving an outboard in neutral somehow tells you something or fixes something? I've spent my entire life around boats and always have, and continue to, witness guys at the dock revving their motors in neutral over and over while complaining they "just don't understand why it doesn't work when I put it in gear."
Russ 13 posted 06-05-2012 12:54 AM ET (US)
I have a Yamaha 90.
I agree with Tom....start with the simple.
I would change out the plugs, sounds like you have one that is fouled.
Check spark plug wire connections.
Under hood fuel filter
Fuel pump
Good Luck
jstarzy posted 06-05-2012 09:35 PM ET (US)
I spoke with Steve at S&S this morning. He's a High tiered certified Yamaha tech. He said " 95 % or more problems like this with a carbed engine are the carbs".
I ran the engine dry last fall during winterization and treated the fuel. Oh well.
After checking the plugs and wires, if they're all ok, I'll trailer it to S&S for the diagnosis and repair this week.
Also....I revved the engine out of gear to try to determine if the oil protection circuit was engaging. Not sure if that applies to in or out of gear but thought it could help the diagnosis.
Thanks for any help. Jim.
Teak Oil posted 06-06-2012 10:05 PM ET (US)
Before you pay a guy to fix your carbs that may or may not be the problem, there should be a fuel filter under the cowl that may be plugged. Switching tanks will not bypass this.
Also pull the plugs and see if they look the same or if one is blacker or wetter than the others.
Russ 13 posted 06-07-2012 12:22 AM ET (US)
If your problem is the carburotor deposits or gummed-up jets and if you are going to store the engine for a long period, say 6 months or more, then drain the fuel from each float bowl (small brass screw on the Starboard lower side of each carb) onto a rag. When the carb is empty replace the screw. Carefully let the rag evaporate somewhere away from any ignition source--no more clogged jets, next time boating :-) Running the engine, with the fuel line disconnected till it stops, still leaves enough fuel in the carbs to gum-up the jets if left unused for a long time.
Jkcam posted 06-13-2012 02:26 PM ET (US)
Jim, ever identify the problem?
jstarzy posted 06-15-2012 08:07 PM ET (US)
So.....the story goes on. Steve at S&S removed the carbs and found a stuck needle valve in the lower carb's float bowl. He freed it up and cleaned all the carbs, re-installed and set up the engine in his tank.
This make sense, when I looked at the plugs prior to dropping it off with him, cylinder 3's plug was wetter than 1 and 2.
However....I then took the boat to Little Silver and started it at the ramp with lower unit down while still on the trailer. It started right up, prime start raised the RPMs and then the motor warmed up and dropped to idle as normal. It began sneezing several times and eventually died. I retried 6 times. Same result. Pulled the boat on the trailer back up to the street.
Called Steve....stumped. He thought the fuel delivery hoses under the cowl may have been gunked or that some debris was working its way to the carbs. He thought dropping it in and going hi speed for a while might blow it out, or, bring it back to him.
So, I removed the oil tank and I looked at the fuel flow to the individual carbs while priming the ball...all good.
Put the boat in the water, started it up, still coughing, though sounding a little better. Took it out to the channel at 1200 RPM all good. Got to the channel at Sea Bright, increased throttle, immediate plane. Full power to 5400RPM, extremely smooth, good roar, familiar speed.
So...bottom line....mid and hi speed are fine. Idle in gear at 7-800 RPM fine. Neutral idle at 700ish coughs and eventually dies....every time.
Thoughts?
I will call Steve in the morning and set up an appointment to bring the Montauk by in the water at his place. I think the engine needs him to set up the low speed jets again and once done, hopefully it will be back to normal.
Or....I will get my Clymers service manual out and give it a go myself. The Yamaha service manual does not have a section on setting up the carbs while running, unfortunately.
But, I prefer to have Steve set it up and get it just right.
Thanks for all.....sorry for the length of this thread but hopefully it may help someone else down the road.
Jim.

jstarzy posted 06-18-2012 10:19 PM ET (US)
Looks like I'll be working on the engine this coming weekend in my slip on the Navesink. I was able to find the carb set up procedure in my Clymers manual.
So...does the sneezing and dying out symptom I'm now experiencing at neutral idle sound like debris in a low speed jet or a set up issue? Steve at S&S recommended I slightly turn the idle adjust screws on each carb to see which one has the most effect on the sneezing. Once isolated, remove the screw completely from the suspect carb after counting turns from full in and then squirting carb cleaner into the screw opening, hoping this frees the debris and solves the problem. He assures me he did a good set up in his tank prior to me picking up the boat. I would return it to him on the trailer but I don't want to do another haul and launch, the only way he says is practical for him to work on it..
Any thoughts?
I hope I don't drop the idle screw!!!!
Thanks...Jim.
davej14 posted 06-19-2012 04:29 PM ET (US)
What is the idle range specification for your motor, 700 seems pretty low. If stalling at 700 RPM in neutral is the only issue I think I would turn up the idle a bit and run it for a while with some fuel treatment like Mercury Quick Clean. It may just self clean with a few hours use and fresh gas.
jstarzy posted 06-22-2012 09:35 PM ET (US)
Got to the Montauk today. The sneezing and stalling was caused by the top carb idle/low speed adjustment screw being turned in too much.
When I found this, I used the Clymer manuals recommendation of turning in the 3 carb screws all the way and backing them off by roughly 2 turns at minimal RPM in gear at the dock. I took them as far counter clockwise as possible, then forward until smooth. Worked great. Idle out of gear at 750 and in gear at 650. Both to spec. All of this done on a 3 gallon tank connected directly with the stock hose and ball, fresh gas, Penzoil marine cleaner and Sta-bil ethanol treatment.
The whole range from idle to 5500 RPM WOT is working as it should.....finally.
Thanks to all for anyone who offered advice.
Now...on to a thread about the alarm system.
Jim.
jstarzy posted 06-22-2012 09:39 PM ET (US)
Got to the Montauk today. The sneezing and stalling was caused by the top carb idle/low speed adjustment screw being turned in too much.
When I found this, I used the Clymer manuals recommendation of turning in the 3 carb screws all the way and backing them off by roughly 2 turns at minimal RPM in gear at the dock. I took them as far counter clockwise as possible, then forward until smooth. Worked great. Idle out of gear at 750 and in gear at 650. Both to spec. All of this done on a 3 gallon tank connected directly with the stock hose and ball, fresh gas, Penzoil marine cleaner and Sta-bil ethanol treatment.
The whole range from idle to 5500 RPM WOT is working as it should.....finally.
Thanks to all for anyone who offered advice.
Now...on to a thread about the alarm system.
Jim.
shskyline posted 08-07-2013 11:53 PM ET (US)
Shanghai Skyline International Co., LIMITED is the leading supplier of outboard parts and is able to supply all the spare parts for YAMAHA, PARSUN, HIDEA from 2HP-75HP, TOHATSU, M3.5B2, M5B, M9.8B, SELVA T15 & T.9.9, MERCURY 55HP & 60HP, and some spare parts for SUZUKI & Honda, and other TOHATSU, MERCURY & some China outboard brand. If you need any spare parts please feel free to contact us.

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Author	Topic: Yamaha 90-HP Two-cycle Outboard Lacks Power
jstarzy	posted 06-04-2012 11:10 PM ET (US) I anticipated a nice ride from Morgan NJ to the Navesink in Rumson in the Montauk, [but the Yamaha 90-HP two-cycle outboard engine] acted up. [The Yamaha 90-HP two-cycle engine seems to have] no power over 3,000-RPM. The throttle movement from 3/4 to full did nothing under load, but [the engine speed response to throttle movement] was normal in neutral for a short spurt. After playing around for 30 minutes in Raritan Bay, I returned back to Morgan. I will take the boat out of the water, examine it again at the end of the week, and head to S&S for repair. I would really appreciate thoughts on what the problem could be. Here are some symptoms and some observations: --no increase of RPM over about 3,200 under load. --full increase in RPM under no load --throttle above 3/4 under load does nothing --no alarm from the oil tank safety limiter though I did not remember to look at the gauge --swapped fuel tanks and ran a direct line without the Racor filter to a tank with fresh gas, no improvement --idle in gear seemed lower than normal at about 500-RPM instead of the normal 700-RPM --engine overall sounded quiter and a bit anemic, even on muffs in the driveway prior to launch. The engine is a 2003 model year two-cycle with just under 110 hours and it is not abused. I just did a water pump [service] a few weeks ago. It went smoothly, though coincidental this problem should happen now. Aside from the trim cap seal the engine has been trouble free, though when running normally. The engine does not seem to get the 1989 Montauk with 20 gallons of gas and me at 170-lbs over about 36-MPH. I read others with the same set up get 40 to 44-MPH. With this current problem, the engine almost seems like it is running on two-cylinders instead of three. I did not have a chance to look at the plugs yet. [I think the causes may be] clogged high speed jets, a bad coil, an ECU, or timing. [I hope the repair] is minor. Thanks for any help--Jim.
Tom W Clark	posted 06-04-2012 11:51 PM ET (US) quote: ...the engine Almost seems like it is running on two cylinders... Yes, it does, doesn't it? Since these Yamaha thee cylinder motor were rather notorious for loose spark plug boots, why not see if that's the problem? Always start with the simple and obvious things first, no matter how unlikely you think they may be. quote: Full increase in RPMs under no load Uh, yeah. That's because there is no load on the motor! Why do so many folks think that revving an outboard in neutral somehow tells you something or fixes something? I've spent my entire life around boats and always have, and continue to, witness guys at the dock revving their motors in neutral over and over while complaining they "just don't understand why it doesn't work when I put it in gear."
Russ 13	posted 06-05-2012 12:54 AM ET (US) I have a Yamaha 90. I agree with Tom....start with the simple. I would change out the plugs, sounds like you have one that is fouled. Check spark plug wire connections. Under hood fuel filter Fuel pump Good Luck
jstarzy	posted 06-05-2012 09:35 PM ET (US) I spoke with Steve at S&S this morning. He's a High tiered certified Yamaha tech. He said " 95 % or more problems like this with a carbed engine are the carbs". I ran the engine dry last fall during winterization and treated the fuel. Oh well. After checking the plugs and wires, if they're all ok, I'll trailer it to S&S for the diagnosis and repair this week. Also....I revved the engine out of gear to try to determine if the oil protection circuit was engaging. Not sure if that applies to in or out of gear but thought it could help the diagnosis. Thanks for any help. Jim.
Teak Oil	posted 06-06-2012 10:05 PM ET (US) Before you pay a guy to fix your carbs that may or may not be the problem, there should be a fuel filter under the cowl that may be plugged. Switching tanks will not bypass this. Also pull the plugs and see if they look the same or if one is blacker or wetter than the others.
Russ 13	posted 06-07-2012 12:22 AM ET (US) If your problem is the carburotor deposits or gummed-up jets and if you are going to store the engine for a long period, say 6 months or more, then drain the fuel from each float bowl (small brass screw on the Starboard lower side of each carb) onto a rag. When the carb is empty replace the screw. Carefully let the rag evaporate somewhere away from any ignition source--no more clogged jets, next time boating :-) Running the engine, with the fuel line disconnected till it stops, still leaves enough fuel in the carbs to gum-up the jets if left unused for a long time.
Jkcam	posted 06-13-2012 02:26 PM ET (US) Jim, ever identify the problem?
jstarzy	posted 06-15-2012 08:07 PM ET (US) So.....the story goes on. Steve at S&S removed the carbs and found a stuck needle valve in the lower carb's float bowl. He freed it up and cleaned all the carbs, re-installed and set up the engine in his tank. This make sense, when I looked at the plugs prior to dropping it off with him, cylinder 3's plug was wetter than 1 and 2. However....I then took the boat to Little Silver and started it at the ramp with lower unit down while still on the trailer. It started right up, prime start raised the RPMs and then the motor warmed up and dropped to idle as normal. It began sneezing several times and eventually died. I retried 6 times. Same result. Pulled the boat on the trailer back up to the street. Called Steve....stumped. He thought the fuel delivery hoses under the cowl may have been gunked or that some debris was working its way to the carbs. He thought dropping it in and going hi speed for a while might blow it out, or, bring it back to him. So, I removed the oil tank and I looked at the fuel flow to the individual carbs while priming the ball...all good. Put the boat in the water, started it up, still coughing, though sounding a little better. Took it out to the channel at 1200 RPM all good. Got to the channel at Sea Bright, increased throttle, immediate plane. Full power to 5400RPM, extremely smooth, good roar, familiar speed. So...bottom line....mid and hi speed are fine. Idle in gear at 7-800 RPM fine. Neutral idle at 700ish coughs and eventually dies....every time. Thoughts? I will call Steve in the morning and set up an appointment to bring the Montauk by in the water at his place. I think the engine needs him to set up the low speed jets again and once done, hopefully it will be back to normal. Or....I will get my Clymers service manual out and give it a go myself. The Yamaha service manual does not have a section on setting up the carbs while running, unfortunately. But, I prefer to have Steve set it up and get it just right. Thanks for all.....sorry for the length of this thread but hopefully it may help someone else down the road. Jim.
jstarzy	posted 06-18-2012 10:19 PM ET (US) Looks like I'll be working on the engine this coming weekend in my slip on the Navesink. I was able to find the carb set up procedure in my Clymers manual. So...does the sneezing and dying out symptom I'm now experiencing at neutral idle sound like debris in a low speed jet or a set up issue? Steve at S&S recommended I slightly turn the idle adjust screws on each carb to see which one has the most effect on the sneezing. Once isolated, remove the screw completely from the suspect carb after counting turns from full in and then squirting carb cleaner into the screw opening, hoping this frees the debris and solves the problem. He assures me he did a good set up in his tank prior to me picking up the boat. I would return it to him on the trailer but I don't want to do another haul and launch, the only way he says is practical for him to work on it.. Any thoughts? I hope I don't drop the idle screw!!!! Thanks...Jim.
davej14	posted 06-19-2012 04:29 PM ET (US) What is the idle range specification for your motor, 700 seems pretty low. If stalling at 700 RPM in neutral is the only issue I think I would turn up the idle a bit and run it for a while with some fuel treatment like Mercury Quick Clean. It may just self clean with a few hours use and fresh gas.
jstarzy	posted 06-22-2012 09:35 PM ET (US) Got to the Montauk today. The sneezing and stalling was caused by the top carb idle/low speed adjustment screw being turned in too much. When I found this, I used the Clymer manuals recommendation of turning in the 3 carb screws all the way and backing them off by roughly 2 turns at minimal RPM in gear at the dock. I took them as far counter clockwise as possible, then forward until smooth. Worked great. Idle out of gear at 750 and in gear at 650. Both to spec. All of this done on a 3 gallon tank connected directly with the stock hose and ball, fresh gas, Penzoil marine cleaner and Sta-bil ethanol treatment. The whole range from idle to 5500 RPM WOT is working as it should.....finally. Thanks to all for anyone who offered advice. Now...on to a thread about the alarm system. Jim.
jstarzy	posted 06-22-2012 09:39 PM ET (US) Got to the Montauk today. The sneezing and stalling was caused by the top carb idle/low speed adjustment screw being turned in too much. When I found this, I used the Clymer manuals recommendation of turning in the 3 carb screws all the way and backing them off by roughly 2 turns at minimal RPM in gear at the dock. I took them as far counter clockwise as possible, then forward until smooth. Worked great. Idle out of gear at 750 and in gear at 650. Both to spec. All of this done on a 3 gallon tank connected directly with the stock hose and ball, fresh gas, Penzoil marine cleaner and Sta-bil ethanol treatment. The whole range from idle to 5500 RPM WOT is working as it should.....finally. Thanks to all for anyone who offered advice. Now...on to a thread about the alarm system. Jim.
shskyline	posted 08-07-2013 11:53 PM ET (US) Shanghai Skyline International Co., LIMITED is the leading supplier of outboard parts and is able to supply all the spare parts for YAMAHA, PARSUN, HIDEA from 2HP-75HP, TOHATSU, M3.5B2, M5B, M9.8B, SELVA T15 & T.9.9, MERCURY 55HP & 60HP, and some spare parts for SUZUKI & Honda, and other TOHATSU, MERCURY & some China outboard brand. If you need any spare parts please feel free to contact us.