SoCal Jet Boats
Tech Talk => Engine Mechanical / Electrical => Topic started by: That Rogers Guy on June 12, 2015, 08:53:32 PM
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So here's my problem guys, I just rebuilt my motor and pump. It's a 454 with stock lower end and 049 cast iron heads I'm running a comp xtreme marine cam 270h grind 544in 547in lift and a edelbrock performer rpm intake and a holley 750 carb to top it off. Ok so here's my issue, the boat was running great but would load up at idle so I check the floats and I had them to high so I corrected that issue so i thought..... then I go out today boats running great I set my idle screws with my vacuum gauge and check the timing all good. Boat ran great all day and then as I come in to the no wake zone head back to the trailer it starts loading up again just like before! It actually died on me once had to keep my foot in it to keep it running. I don't understand what's going on? Once I put it on the trailer I fired it up and it seemed to run fine on the trailer. Any help would be great I pulling my hair out!
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Mine did this too.. I had to adjust the float needle and it ran great after I adjusted it
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What more can you tell me about your set up?
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What else do you want or need to know GT? Ill tell you all if you can fix it :) I adjusted the floats already before this happen agian.
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Carb is 4779-9 750 double pumper.
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There are a few possibilities.
Do you know what your distributor advace curve is set up like? What is the timing at idle?
How low are you trying to get our to idle?
Does it smell fat?
Any chance of water in the fuel at all?
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I don't know what the curve in the dizzy but I set the total at 34. I had the idle set at 8-900 before she started acting up. It did smell just a touch fat at idle but not bad just that little sweet smell. The water in the fuel could be but I'm running a fuel/water separater, the mercruiser type.
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I just thought of something GT.... im running a Mallory dist. that I was points but I pulled them out and put one of those ignitor kits in. Thinks this could be causing my headache
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How do the plugs look??? When you changed to a Mallory unit did you adj the plug gap??? No I don't think it has anything to do with it.
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I didn't change the unit just the internals I did this before I went through the motor. The plugs were good nice golden brown but ever since I went through the motor they have been black this is only the third time out on the motor. I'm running spark plug gap at 40
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I still say check the tires
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I didn't change the unit just the internals I did this before I went through the motor. The plugs were good nice golden brown but ever since I went through the motor they have been black this is only the third time out on the motor. I'm running spark plug gap at 40
You might just for fun run the floats again, ate the air bleeds clean and do you have a power valve in that carburetor?
It might be worth installing a new power valve, it should have a pretty low (numerical number indicates manifold pressure the valve opens) numbered valve. I start with 4.5 normally.
GT
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I will check the floats agian, currently it's got 6.5 power valves front and back. Its pulling 18-19 inch pounds of vacuum at idle.
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There shouldn't be a power valve in the rear...
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There shouldn't be a power valve in the rear...
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Unless the wrong metering plate was installed.
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I will check the floats agian, currently it's got 6.5 power valves front and back. Its pulling 18-19 inch pounds of vacuum at idle.
See if your local parts store has a 4.5 and a block and a bowl gasket.
IMHO be way more better.
Not saying that is the problem, but it will have a cleaner transition.
GT
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Unless the wrong metering plate was installed.
True statement.
If there is a Pv on the secondary side that could cause the issue,. As it would be drawing excessive fuel during off idle conditions.
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Ok, I could have my head up my ass! I was thinking it had a PV in the rear. I have a 5.o PV should I try that? I thought per the Holley instructions you take your idle vacuum and divide it in half to get your power valve size? GT can you teach me your thoughts on this?
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It's only having the rich/loading up issue at idle? Once I stand on it she clears out and seems to run good till I come back to idle she wants to die.
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Ok, I could have my head up my ass! I was thinking it had a PV in the rear. I have a 5.o PV should I try that? I thought per the Holley instructions you take your idle vacuum and divide it in half to get your power valve size? GT can you teach me your thoughts on this?
Everything you read in the instructions will apply to a car. A car has a higher engine load at lower rpm than a jet (understatement).
The power valve is there to fasten things up energy the air flow starts to pass up the fuel delivery under acceleration.
Yours at the stock level would come in way to "soon" and cause it to run fat at lower engine speeds. By dropping the size of the valve, it will transition later when the load is actually high enough to accept (read "need") more fuel.
If you have a 5.0 and you can do it without damaging the gaskets, I would do it. It will not yield negative results at all.
Just a side note, I always coat the bowl and metering plate gaskets with motor oil. You can reuse them several times. (I'm a cheap SOB).
GT
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It's only having the rich/loading up issue at idle? Once I stand on it she clears out and seems to run good till I come back to idle she wants to die.
Are you adjusting the idle screws with the engine cold?
You should be adjusting them with the engine hot.
The engine requires a tad more fuel when cold. (The whole idea behind a choke ).
GT
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Cool thanks GT! I will switch out the PV to the 5.0 also I adjusted the idle screws after the motor warmed up. They are only out half a turn, does that sound right?
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Cool thanks GT! I will switch out the PV to the 5.0 also I adjusted the idle screws after the motor warmed up. They are only out half a turn, does that sound right?
Not really.
I would have expected about a turn out.
Are you trying to adjust the idle screws on the trailer?
This is very difficult, virtually never netting proper results.
Warmed up on the water. JMO.
GT
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No, It was warmed up on the water