9.9 won't run above an idle

Post here for issues with outboard engines (i.e Yamaha 9.9) on PDQ yachts
amytom
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9.9 won't run above an idle

Postby amytom » Sun May 16, 2010 11:35 am

I have a mystery engine that I acquired. I say mystery because it wasn't installed and it had the oil filter, one spark plug, and fuel filter in a plastic bag inside the housing. It was also missing the oil filler cap and dip stick.

My starboard engine had an oil seal failure at the top under the coils so I swapped the needed parts over to this engine to try. I got it to run at an idle no problem but it won't run at speed and has a hard time idleing after trying to run at speed. It starts to accelerate okay but then just bogs down. I swapped over the carb, fuel pump, all fuel delivery hoses, CDI, and HV coil. Both cylinders have over 120PSI compression, the oil pressure switch is working and indicates good pressure, no excessive smoke or oil in the water discharge. I changed the oil and saw small bits floating in it but it was fairly clear oil and the compression appears okay.

Any thoughts?

If I didn't hate borrowing money I'd just buy two new engines. But being poor...

Tom

Marc Gershel
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Re: 9.9 won't run above an idle

Postby Marc Gershel » Sun May 16, 2010 1:00 pm

Has the exact symptoms that my engine had, but my problem was a major oil leak. Sorry , I can't offer any other help.
Marc

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Re: 9.9 won't run above an idle

Postby carib sailor » Sun May 16, 2010 1:58 pm

There is a chance (depending on the model of engine) that it's equipped with the Yamaha "Alert" system.

The Alert system engages when the oil pressure is too low. One the alert system engages the engine will be limited to about 2000 RPM.

You won't be able to increase RPM's as long as the Alert system is engaged.

There are a number of things that can cause the Alert system to engage. Low Oil Pressure due to low oil or a leak, or a defective oil pump for starters. The oil pressure sending unit could be defective. There are other possible causes but these are the most common.

Check your service manual, there is a method for temporarily bypassing the Alert System for brief diagnostics purposes. If bypassing the Alert system cures the symptom do NOT be tempted to permanently bypass the Alert System.

Find and fix the root cause of the problem or you stand a very good chance of blowing the engine.

I hope this helps. Best of luck.

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Re: 9.9 won't run above an idle

Postby thinwater » Sun May 16, 2010 2:53 pm

Separated e-10 will do exactly that. Try fresh gas.

As stated, the oil pressure system will do that, but it should idle well.

Faulty thermostatic choke will do that.

Dirty main jets too, but generally idle is more of a problem.

These are ones I have come across. I'd flush the carb first.
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amytom
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Re: 9.9 won't run above an idle

Postby amytom » Sun May 16, 2010 6:02 pm

I've tested the oil pressure switch and it's sending the "oil ok" signal to the CDI. (grounded when not running and open/full voltage when running)

I swapped the carb with one that I thought was running well from another engine, (the engine now in pieces with a shaft seal leak)

I didn't check the power coming over to the thermostatic choke.

When I get this one back on the stand I'll also check the intake manifold gasket for leaks.

Thanks for all the replys, especially on a Sunday.

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thinwater
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Re: 9.9 won't run above an idle

Postby thinwater » Sun May 16, 2010 10:46 pm

In my case it wasn't the power to the choke - as near as I could tell it just was not moving properly and not opening completely. Not a problem at idle, but not enough air to really run, and then it would bog down and act flooded.
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amytom
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Re: 9.9 won't run above an idle

Postby amytom » Tue May 25, 2010 7:57 am

I swapped the carb again and now it's running up to full speed. Has a bit of a whine to it though, also saw something floating in the oil. But cooling is good and no smoke; do have a bit of a water leak at the exhaust/cooling cover on the side of the block but that should be easy to fix.

The carb that had the problem is soaking in a gallon can of carb cleaner for several days. It seam these cleaning products have gotten weaker (EPA?) and you have to let them soak with the plastics removed for extended periods of time.

Also, after seeing so many of the engines at various stages of disassembly I've learned the importance of rinsing the engines very well after every use. Some people have installed rinse tubes into the top of the thermostat housing, this doesn't rinse very well at all, it also doesn't allow you to test the water pump on the stand. (the water pump is spining dry while running this way). The proper way to rinse the engines is to put a flushing fitting into the lower unit then route a hose to the top outside of the cover.
After an engine starts to get corroded in the cooling passages it will die. Some repairs can be done but the cost of parts and your time will quickly grow to the point of a new engine. I've got quite a few parts laying around from too many engines but I'm still going to start setting aside some cash to buy new engines in the next two years.

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Re: 9.9 won't run above an idle

Postby Dan White » Wed Aug 07, 2013 7:38 pm

This is an old topic but, boy, did it help me. We had just left the Rappahanock River area, headed for Baltimore last Saturday to head home and have the boat hauled for a bottom paint job. Everything was fine for about 30 minutes, until, all of a sudden the port engine made some strange surge-like noises and and no matter what, would not run above an idle. It would start fine and idle fine, but as soon as throttle was applied it sounded like it was flooding out.
Not having the benefit of access to this forum while on the Chesapeake, we had no idea about the Yamaha - alert system referred to in the previous posts, so we checked everything we could think of - except the oil. It never occurred to me to check the oil, because I had just checked it and it was fine.
Once we (finally) got home, I started reading this topic, and, voila, there was the mention of a possible connection to an oil problem.
Tonight I went to the boat and checked the oil and, sure enough, it is bone-dry. Obviously that begged the question -- where did it go and why?
Since the boat was on the hard, I observed the leaking as soon as I put a new quart in. Looks like the oil dripped out near the bottom at 2 small holes. I am sure someone on this forum knows what they are, but I don't. I have a call into the Yamaha dealer nearby to help fix the problem.

Anyway, many thanks to those who keep this forum going, as well as those who submit the information. This is a great resource.

Marc Gershel
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Re: 9.9 won't run above an idle

Postby Marc Gershel » Thu Aug 08, 2013 9:34 pm

Hi Dan, I'm sorry for your problem, but thrilled that my 3 year old post helped. It turned out that the oil pan had a major ieak. Probably corrosion. I had intended to remove the engine and swap out the pan with one from an old engine that I had. After looking into what was involved I decided it was too much of a PITA. Since the engine had about 1800 hours, I decided to look for a good, low hour engine, and found one. I would have bought a new engine, but at that time the new Yamahas didn't fit. I understand now they do.
Marc


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