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nhinshoreangler

Help. Carbureted VMax 150 Power Loss

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Just when you think your outboard is running flawlessly......

 

Was running at 4000 RPM this morning and gave throttle, a slight hesitation. No big deal it only happened once. Boat ran fine for about a half an hour after that.

Was running at 4000 RPM again gave throttle, motor would not go over 4400 RPM's, tested it a couple times between 15 minute drifts, still would not go over 4400 RPM's.

On the way back to the ramp the motor started to run terrible at the lower RPM's as well. 

 

Any suggestions as to what the issue could be?

 

Thank You!!

 

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There are a few things that can cause your situation, but we would need some more info first.  Fuel would be #1 and spark would be # 2.  There are other things but not as often.    

- Has the boat sat for a while?

- How old is the fuel?

- Is it Ethanol fuel?

- When was the last time you checked the water separator for water or contaminates? 

- How old is your primer ball and fuel lines?  Are they collapsing or leaking air?    

- When was your last spark plug change?

If fuel is crystal clean along with the carbs, you may have lost a coil or two.  

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23 minutes ago, Lap it Up said:

There are a few things that can cause your situation, but we would need some more info first.  Fuel would be #1 and spark would be # 2.  There are other things but not as often.    

- Has the boat sat for a while?

- How old is the fuel?

- Is it Ethanol fuel?

- When was the last time you checked the water separator for water or contaminates? 

- How old is your primer ball and fuel lines?  Are they collapsing or leaking air?    

- When was your last spark plug change?

If fuel is crystal clean along with the carbs, you may have lost a coil or two.  

The boat sat over the winter but I have used it about 10 times in the last 3 weeks with the start of striper season. All was fine until today. I keep the fuel level low because I fish shallow and my fishing area is only 1/2 mile from the ramp. I have brought the fuel level down to 1 bar two or three times this year and added 10 gallons with a can of Seafoam each time.  I keep the boat at the house so I use gas with ethanol from a gas station. Separator was changed over the winter and I just put another one on this afternoon, after I got home. I have not tested the boat yet with the new separator. The ball and lines are original 2005 but the ball seemed very firm as it always is. The plugs were changed last week. thank You!

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One more thing.

When the boat was winterized in the fall, the mechanic replaced the the filter and did not use the Yamaha brand "blue" 10 micron filter. He used a Sierra filter which is white and about half the size of the Yamaha. I'm going to run the boat (with the new Yamaha filter on)on a local lake this morning and see if it's the same. Thanks again

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1 hour ago, nhinshoreangler said:

One more thing.

When the boat was winterized in the fall, the mechanic replaced the the filter and did not use the Yamaha brand "blue" 10 micron filter. He used a Sierra filter which is white and about half the size of the Yamaha. I'm going to run the boat (with the new Yamaha filter on)on a local lake this morning and see if it's the same. Thanks again

Please keep us posted, I have the same engine and am watching this closely!

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17 hours ago, nhinshoreangler said:

I keep the boat at the house so I use gas with ethanol from a gas station.

 

17 hours ago, nhinshoreangler said:

The ball and lines are original 2005 but the ball seemed very firm as it always is.

Has nobody picked up on these two statements above, geesh fella's, ya'll all are losing your touch! :DThe fuel lines degrade quickly with ethanol unless you got the very very expensive fuel hose with a liner which I doubt. The fuel line and bulb are 15 years old, they are over due. Just to ensure it is a possible fuel problem, connect a portable fuel tank, like for a jon boat and run it and see if it resolves your problem.

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Ran the boat on the lake for about 20 minutes and it ran perfect. The problem was either the fuel water separator, plugs ( I also resnugged the new plugs I put in a week or so ago), none were loose or maybe an overheat issue.

This motor has been so flawless for me (1300 hrs)I have not done much to it other than change plugs, lower gear oil, separator. The mechanics around here say "if it isn't broke don't fix it.

I do plan on bringing it to a mechanic during the off season and cleaning carbs, replacing fuel filters, fuel pumps, fuel lines......... 

Any thing else you recommend for preventative maintenance?

Thank you again for all your help, I really appreciate it.

 

 

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If it idles fine, runs thru the RPM range fine and reaches max RPM without issue there is no need to have the carbs pulled and cleaned.  

I do however recommend the following:

- New fuel line from tank to engine

- New primer ball (I use the merc OEM ball.  It has two check valves apposed to yamaha's single)

- New fuel pump assembly w/ new gasket on the block (If the fuel pump is 15 years old, its time for a new OEM pump for reassurance

- New inline fuel filter under the cowling

- Check poppet valve and thermostats and change accordingly if needed (I would replace them all if they also haven't been done in 15 years)

These are all easy fixes and can be done by most any DIY kind of person, especially on your simplistic engine.  

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10 minutes ago, Lap it Up said:

If it idles fine, runs thru the RPM range fine and reaches max RPM without issue there is no need to have the carbs pulled and cleaned.  

I do however recommend the following:

- New fuel line from tank to engine

- New primer ball (I use the merc OEM ball.  It has two check valves apposed to yamaha's single)

- New fuel pump assembly w/ new gasket on the block (If the fuel pump is 15 years old, its time for a new OEM pump for reassurance

- New inline fuel filter under the cowling

- Check poppet valve and thermostats and change accordingly if needed (I would replace them all if they also haven't been done in 15 years)

These are all easy fixes and can be done by most any DIY kind of person, especially on your simplistic engine.  

Great advice thank you. I going to insist my mechanic does the above. 

 

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I was able to run the boat through all RPM ranges this morning for an extended period of time. The motor runs great, no issues. It appears there was some water in the fuel and getting rid of the Sierra fuel filter and putting back in the Yamaha 10 micron made all the difference.

 

Thanks again!

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Wanted to do a final follow-up which may be helpful to others. The problem came back again so I took it back to a different dealer. Turns out the bowls of the carbs had "varnish" build up and after cleaning the carbs the boat has run perfect for about 50 hours. There was also some fine debris in the bowls which made the power loss problem variable. With further inspection of my fuel lines and fuel tank by the dealer, there was no water and the fuel lines still look great. While in the there, I had the dealer replace the original thermostats. They were amazed the thermostats were original, flushing with fresh water after every use seems to help a lot. 

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