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Old 09-03-2011, 09:03 PM
mmthorn mmthorn is offline
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Boat: Mastercraft, Maristar, 1998, MX Plus
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1998 Maristar Won't Run over 2800 RPM

My 1998 Maristar just started having a problem where the engine dies at around 2800 RPM. Sometimes the engine will stay running if I pull the throttle back to the idle position. Other times the engine will completely die.

I figured it might be a fuel problem. This boat has an external electric fuel pump (high pressure type with two inlets) that is attached to the engine.

Here are the things I have tried.

- Replaced both fuel filters.
- Cleaned the screen on the inlet to the fuel pump and the screen on the inlet to the fuel pick up tube. Both were clean by the way.
- Added a fuel injector cleaner product.
- Measured the fuel pressure while driving (30 psi per the owners manual).
- Measured the fuel pressure at key on. (30 psi for a few seconds and then drops to zero). Is this correct?
- Replaced plug wires and plugs.
- Checked compression on all cylinders (190-200psi when engine is warm).
- Kill Lanyard is attached.
- Oil pressure seems to run between 40 and 50psi.
- Checked the engine ground. Clean


Any ideas? Does anyone understand how this dual inlet high pressure fuel pump works?

Thanks,
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Old 09-03-2011, 09:19 PM
mmthorn mmthorn is offline
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Boat: Mastercraft, Maristar, 1998, MX Plus
Location: Midwest
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Just thought I would mention that I also hooked up a diagnostic tester and there were no engine codes. The Throttle position sensor checked out with the diagnostic tester also.
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Old 09-03-2011, 10:28 PM
mmthorn mmthorn is offline
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And another thing: I replaced the severely corroded distributor cap and rotor. Did not help.

The motor has 515 hours. I have owned since new.
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  #4  
Old 09-04-2011, 12:49 AM
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JLeuck64 JLeuck64 is offline
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Boat: 98 Prostar 190 Stars & Stripes, LT1
Location: Oregon
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What's the fuel pressure like when it dies? Still thinking you may have a fuel delivery problem and would like to see what the fuel pressure is like when the problem is present.
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  #5  
Old 09-04-2011, 12:52 AM
FrankSchwab FrankSchwab is offline
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I don't have any help for you, but I'm real interested in any responses you get.

You've checked everything I'd check.
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Old 09-04-2011, 07:23 PM
mmthorn mmthorn is offline
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I just got off the lake. I ran the boat with the fuel pressure gage attached. The gage reads 30 psi before, during and after the stall. The stall is pretty consistent at around 2800RPM. It seems like the fuel delivery system is working fine. I also watched the two injectors on the TBI and they seemed to be fine until the stall at which time they cut back their flow.

Does anyone have any ideas? Could it be something related to the Ignition Control Module or the ECM?

Thanks for reading this post.
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Old 09-04-2011, 08:35 PM
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Kell Kell is offline
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I seem to recall reading here that 40-50 psi at the shrader valve on the fuel rail? Sorry don't have anything to add but I hope you get this resolved.


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Old 09-04-2011, 08:53 PM
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Quote:
Originally Posted by Kell View Post
I seem to recall reading here that 40-50 psi at the shrader valve on the fuel rail? Sorry don't have anything to add but I hope you get this resolved.


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Old 09-04-2011, 09:42 PM
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JimN JimN is offline
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The pressure in '98 would have been 30 pounds, so that seems OK, although I would look at the anti-siphon valve and fuel pickup tube.

Remove all of the relays and inspect them for corrosion. If the motor box doesn't have good circulation when the temperature cools and warms up, condensation will take a heavy toll. Make sure the grounds on the engine are spotless and there's no resistance between the ground stud and the battery post.

The pressure will drop at key ON if you don't start it because the initial pressure is from the pump priming. Coast Guard regs require electric fuel pumps to stop if the engine stops.

How old are the plug and coil wires?
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Old 09-04-2011, 10:38 PM
mmthorn mmthorn is offline
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Boat: Mastercraft, Maristar, 1998, MX Plus
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- The ground at the battery and on the engine look spotless.
- The plugs and wires are brand new. I just replaced.
- I checked the pick up tube and the screen to the inlet of the fuel pump. Both were clean.
- I will check the relays for corrosion the next time I am at the lake.

- Tell me about the antisiphon valve. I haven't checked this out.
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