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Yaboycbrooks

loosing power after about 1 minute

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Yaboycbrooks

I have had this boat for about 3 years and I finally have it ready for the lake. I put it in 3 or 4 times and when I get it away from the dock it runs great as long as I am going really slow (or slow enough for it not to plain off). However, when I get in the throttle, like when you would try to start pulling someone skiing or on a wake board, it starts losing power like it is running out of fuel. I have checked the carburetor and put clean non ethanol fuel in it. As I mentioned before, the engine runs great as long as I don't get in the throttle. What to change next???

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Rednucleus

More specifics on the boat please - motor, +/- carb etc. You have been getting it ready - what did that entail?

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formulaben

When is the last time the fuel filter was changed?  Probably unlikely, but crack open a fuel filler cap and see if it makes a difference to eliminate a venting issue.

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Yaboycbrooks
16 hours ago, Rednucleus said:

More specifics on the boat please - motor, +/- carb etc. You have been getting it ready - what did that entail?

It is a 1988 with mercruiser 5.7 (350). The fuel filter was changed a year ago and I have taken it off and checked it. I also checked the small mesh filter at the carb and it was clean. It runs great except when you get in the throttle. Could the fuel pump possibly be loosing pressure when it is under a load? The reason I ask is, when this happens, I can get off the throttle and let it "catch up" so to speak and the motor runs smoothly.

 

The getting it ready parts was replacing the stringers, flooring and complete interior of the boat. I service the engine while all of this was being done. The frustrating thing is that I have not even run a complete tank of gas!!

15 hours ago, formulaben said:

When is the last time the fuel filter was changed?  Probably unlikely, but crack open a fuel filler cap and see if it makes a difference to eliminate a venting issue.

I will check this option.

 

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malibu2004

When was the last time the carb was rebuilt? Fuel Filter? PCV? 

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JasonK

Carb prob is my first guess. Did you add or have a water separating fuel filter. I added a small see-through filter once a long time ago and I had problems. It turned out is was sucking air at the filter connection.

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Rednucleus

Sounds like carb to me too. Check float levels, accelerator pump

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Falko

IF it dies right away as soon as you open the throttle, I doubt it is the fuel pump. The carb will hold a decent amount of fuel in it which once drained, it will die. But that could be your problem as well, if it hasn't run in a while, the floats might be stuck down. In a carb, you suck the gas into the engine, you don't push it with the pump. Is it an electric or mechanical fuel pump?

Another thought is your primary jets are clogged, your idle jets let the boat run properly at idle, get into it and blah. The primaries won't allow any fuel in. Remember carbs "pull" the fuel, nothing pushes the fuel through the jets except atmospheric pressure.

Another thought is your choke plate isn't opening.

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Yaboycbrooks
2 hours ago, Falko said:

IF it dies right away as soon as you open the throttle, I doubt it is the fuel pump. The carb will hold a decent amount of fuel in it which once drained, it will die. But that could be your problem as well, if it hasn't run in a while, the floats might be stuck down. In a carb, you suck the gas into the engine, you don't push it with the pump. Is it an electric or mechanical fuel pump?

Another thought is your primary jets are clogged, your idle jets let the boat run properly at idle, get into it and blah. The primaries won't allow any fuel in. Remember carbs "pull" the fuel, nothing pushes the fuel through the jets except atmospheric pressure.

Another thought is your choke plate isn't opening.

How do I determine if the choke plate isn't opening? I have had the breather off the carb while the engine runs on the water hose, but I don't want to get the engine too hot so I don't run it wide open in my drive way.

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Falko

You can always get the engine warm, then jimmy it open and take it for a run and see if it makes a difference.

I think those engines had an electric choke so it wouldn't be too surprising if it isn't working.

Edited by Falko

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Rednucleus

Curious also how old is the gas - how long did it sit in the carb w/o running?

Two things you can check on the water or on the hose -  With breather off, motor cold, start it - choke plate should start off closed but fully open as motor warms up. Also, rev motor while looking into carb, should see fuel spray from accelerator pump down carb throat. This functions to negate any lag - kind of what you are describing.

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REW

If the boat sat for awhile with gas in the carb I would suggest a carb rebuild.  Not to difficult to do, and there are lots of youtube videos that will take you through the process step by step.  

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Yaboycbrooks
On ‎7‎/‎8‎/‎2016 at 3:31 PM, Rednucleus said:

Curious also how old is the gas - how long did it sit in the carb w/o running?

Two things you can check on the water or on the hose -  With breather off, motor cold, start it - choke plate should start off closed but fully open as motor warms up. Also, rev motor while looking into carb, should see fuel spray from accelerator pump down carb throat. This functions to negate any lag - kind of what you are describing.

I put new non ethanol gas in the boat with a can of sea foam. I have had the carb rebuilt and new gas in it. I top off the gas tank every time I go to the lake. I don't feel like it is the gas, but I have not been able to run a complete tank through the carb at one time because when starts acting up I just cruise around until it is time to take the boat out go home. I have a guy going with me to the lake tonight to drive the boat so I can watch the carb like you described above. I will report back. Thanks, Chris

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Woodski

@Yaboycbrooks:  as noted above, the symptoms sound like the accelerator pump is not working, you can check by simply actuating the throttle and see if the pump squinters do their thing.  Other options include debris in one of the key passages.  Also, I have seen anti siphon valves (located on the fuel tank vent line) stick and create a vacuum in the system.

If the fuel system is all correct, perhaps you can check ignition timing to make sure the advance system is working properly, if it is not, you could see those similar symptoms.

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