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Repairs to Engines and Boats BOAT means "Break Out Another Thousand" to many of us. Discuss your engine and hull repairs here.

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Old 04-02-2016, 08:40 PM   #1
Shootinfish
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Angry Yamaha bogging down under load but idles and runs at speed no problem?????

Originally posted this in an on going thread but figured I would start a new thread so everyone could see it in hopes that the more that see it, the better my odds are of a solution.

I have been dealing with this issue for OVER A YEAR NOW. Nobody I have taken the boat to can seem to fix it. I keep spending and spending and each time I hear "I think we solved your problem" first test run out and it does good at first but eventually goes right back to what it was doing before. I have taken it to 3 different places with no avail so maybe you have an idea of something I could try if this has happened to you or know of the problem.

Motor: 1998 115hp Yamaha precision blend

What the boat is doing:

Cranks up no problem. Idles on trailer and in water no problem. can put it in gear and idle around in marina no problem. when I get out of no wake zone and give it some throttle, as soon as it gets under load it wants to bog down and try to shut off. HOWEVER, if I hit the electric choke when it starts to bog down it throws "more fuel" to it and it will then take off. it seems to do it between 3-7mph. Once I hit the choke and it jumps past the part where it wants to bog down and I give it more throttle, it will run like a new motor from about 8mph to WOT and wil run anywhere between those speeds flawlessly all day long. as soon as I stop the boat and start to take off again I have to give it throttle until it starts to bog, quickly hit the choke while giving it more throttle and then it will take off. if I don't give it choke when it starts to bog it will cut off. again, it will sit in idle all day no problems. it will idle around in gear all day with no problems and run at any speed all day with no problems past 7-8mph. Anything in-between in gear idle speed and about 7mph and I have to continually bump the choke to keep it going (like if I want to troll between 3-7mph, I have to continue to bump the electric choke to keep it from bogging and cutting off) it seems to be just when I put it under load is when I have the problem. even driving it on the trailer is a pain in the ass sometimes cause when I put it under load trying to drive it on the trailer it wants to bog down.

What I have done, and what mechanics have done.

1) Replaced complete fuel line from tank to motor incase there was a pinhole leak somewhere.
2) Rebuilt the carbs/cleaned injectors
3) Changed spark plugs and wires
4) Replaced the pump diaphragm
5) Replaced the priming bulb
6) Checked compression- all cylinders were very good
7) A bunch of other stuff that ill probably only remember if someone mentions it :/

Have always used fuel stabilizer religiously in every fill up.

Do you know of anything I could possibly try to help? Have you seen this problem before? If so what was the fix!?!?!?!?! its been so long since I haven't had to deal with the bogging that I have about just got accustomed to going through the motions as if that's how your supposed to run one now
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Old 04-02-2016, 08:49 PM   #2
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Re: Yamaha bogging down under load but idles and runs at speed no problem?????

Could this be a fuel air ratio problem? Maybe the spring is worn out and the fuel air adjustment screw has worked its way in or out. Could this be a possible problem??
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Old 04-03-2016, 07:57 AM   #3
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Re: Yamaha bogging down under load but idles and runs at speed no problem?????

i had the same issues with my 2011 yamaha 90hp 4 stroke , its from water in the fuel causing the issues , check the high pressure system screen
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Old 04-03-2016, 08:44 AM   #4
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Re: Yamaha bogging down under load but idles and runs at speed no problem?????

Thanks for the reply slinginsteel. I have drained all the fuel out of it twice over the last year and replaced the fuel water separator and filters both times thinking water may be the culprit. Neither time helped. I have also ran it down to fumes several times and tried refilling at different places thinking maybe there was water in the gas where I filled up. still does it. I can understand getting bad gas once or twice throughout a little over a years time but to get gas at dozens of different places every single time I filled up is a little suspect. I know boat motors are and can be a pain in the ass but im to the point now that if it didn't hurt so bad to pull my hair, I wouldn't have any left on my head.
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Old 04-03-2016, 09:28 AM   #5
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Re: Yamaha bogging down under load but idles and runs at speed no problem?????

Take a look at where the mechanisms hook up from the cable to the carburetor, where the lever rest against the carburetor You look at the diameter of it and then find a thick wall rubber hose, usually half-inch to three-quarter inch long is all you need. Stick it on there, now it's in neutral it will be idling just a taste above what it idled before, which when you nail it it's already got that little bit more RPM to get it going.
I did this on a Suzuki 30 horse, and recently a 150 Johnson.

Second thing to rule out moisture or other fuel tank problems get a remote 6 gallon gas can and run it with that.
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Old 04-03-2016, 09:58 AM   #6
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Re: Yamaha bogging down under load but idles and runs at speed no problem?????

kehloken,

Im not sure im following where and what to put the rubber hose on. however I do understand that by doing what you recommended, it will increase the idle speed and it would make sense that it would give it that extra bit of help it needs. couldn't I just adjust the idle screw to make it idle faster? I had thought about doing this but wasn't sure if increasing the idle speed would cause more problems down the road due to it being harder on the gears going in and out of gear at a higher speed. Would running it at higher speeds cause more wear on the gear? If not ill definitely give that a try! Thanks for the advice. It is greatly appreciated.
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Old 04-03-2016, 10:31 AM   #7
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Re: Yamaha bogging down under load but idles and runs at speed no problem?????

My brother had some issues on his Yamaha.The ethanol had ate his fuel lines and left a buildup in his tanks.Engine was bogging.He cleaned the tank and changed the lines.Still bogged so he took off the carbs and cleaned them.Still problems so he rebuilt them.Runs great now.Rubber parts had ate away.Yamaha has new designed filters for ethanol fuels also.I had similar problems on my suzuki 4 stroke.I used mine often so it was just a line change,ethanol treatment for a day and no more ethanol fuels.
You may want to check your stator(spelling?)also.Had a 70 hp Mercury that bogged on load and the stator was bad.
Boats can be a pain in the ass.
Any gas motor boils down to fuel,air and fire.Find whats lacking.
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Old 04-03-2016, 10:54 AM   #8
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Re: Yamaha bogging down under load but idles and runs at speed no problem?????

Obligated,

I Know exactly what you mean about them being a pain in the ass. I love the boat and the motor runs like new except for this irritating problem. still gets me to my spearing grounds and out in the blue water trolling for hoo's and dolphin and am completely confident in it that it will get me back. However, at the same time, I would like to run it off a damn cliff because of the "mystery" issue. I don't know why checking/replacing the stator hadn't crossed my mind. I will order one today and try that. Thanks!
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Old 04-03-2016, 01:06 PM   #9
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Re: Yamaha bogging down under load but idles and runs at speed no problem?????

1. Contact the manufacturer and inquire as to what seals in the motor need to be replaced due to the ethanol

2. Sticky timing advance. If you don't have electronic timing, check your vacuum hose to the timing advance for leaks and/or check the smoothness/lubrication of the timing advance mechanism under the flywheel. If you do have electronic timing, buy a new/used one, try it out, take it back if it didn't fix it.
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Last edited by Marcus; 04-03-2016 at 09:35 PM.
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Old 04-03-2016, 09:04 PM   #10
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Re: Yamaha bogging down under load but idles and runs at speed no problem?????

Marcus,

Thanks for the suggestion. Again, this is exactly why I posted here. I am getting possibilities that I couldn't think to try. Probably because of all the brain cells I have lost over the year beating my head over the cowl. Ill definitely add this to the list of things to try. Thanks again!
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Old 04-03-2016, 09:38 PM   #11
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Re: Yamaha bogging down under load but idles and runs at speed no problem?????

No problem. Please keep us posted as to the fix. It's always nice to know. I beat my head a bit on such an issue that I'd wished I'd someone give me a hint on.
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Old 04-08-2016, 08:39 PM   #12
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Re: Yamaha bogging down under load but idles and runs at speed no problem?????

When the carbs were cleaned did you/the tech do the link and sync procedure after? This sync your throttle plates together and throttle plates to your timing advance. If not at a minimum start there. Also try the easy stuff:

Drain the carb bowls into a clean catch can. Is there trash in the gas? Completely fix the source of the trash (deteriorating lines like others mention) or you'll just keep sucking it in.

Engine off, pump primer ball til hard. Does it stay hard? If not find where is the fuel going/fix.

Engine on, have a buddy pump the primer ball through the offending rpm range without choking it. Does it still bog out?

Test the fuel pump for a broken membrane (Google it...it's easy). A cough or sneeze can blow a hole in a membrane quickly. Since you have this bogging issue your more prone to having either one of those so your new membrane might be shot.

Since you are choking to get through that range it sounds like it's running lean at least in the given rpm range. Two strokes, even precision blends don't like to be run lean so try to figure it sooner than later. Good luck!

Last edited by cheetah chrome; 04-08-2016 at 08:48 PM.
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Old 04-24-2016, 04:36 PM   #13
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Re: Yamaha bogging down under load but idles and runs at speed no problem?????

Hey guys. I just want to thank each and every one of you for your replies. All that helpful info went into the file labled boat in the back of my mind for future reference. Thanks to your replies, I have found the problem. The only problem I have now is not knowing what could be causing the problem. The problem is the bulb isn't staying hard. When I first put it in the water, I can pump it up hard pretty quick with just a couple squeezes. After running about 15 miles and stopping then try to take off again it boggs. So when I checked the bulb I noticed it was squishy and almost like it was full of air with no fuel in it period. Sometimes it will pump right up after running it but most of the time it takes like 5 minutes of constant squeezing to get it tight again. Once it gets tight again I can take off no problem. So what I need to know now is how to fix the problem. What would cause the bulb to loose pressure and not stay hard? I don't think there is a leak since I can't smell nor find ang gas in the hull and once the bulb gets hard I continued to apply pressure to look for leaks at the fittings going into the motor and filter and couldn't find any. So if there is no leaks, why won't the bulb stay hard? Cheetah chrome had asked me if the bulb stayed hard when the motor was running. The answer would be no. I'm assuming since you asked the question you know the solution. Thanks again guys!
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Old 04-24-2016, 10:04 PM   #14
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Re: Yamaha bogging down under load but idles and runs at speed no problem?????

How old is the bulb? They changed them a few years back due to the ethanol. They doubled in price too. Check iboats.com forum. They've helped me with my motors.
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Old 04-24-2016, 10:45 PM   #15
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Re: Yamaha bogging down under load but idles and runs at speed no problem?????

Uhm....I'm going to ask the obvious here....Is this a ventilated gas tank? Is there a some ventilization that keeps a suction from occurring when fuel gets sucked out of it? If it's a sealed gas tank, there's an air release valve on top of the gas cap that has to be opened.
I'm sorry if this has offended your intelligence but I had to ask, I've seen more than one person make this same mistake.
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