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aggie08

Engine Bogs Down at High RPM - Monsoon 325

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aggie08

Hey guys,

After 7 years of ownership of a 20+ year old boat, I think I'm finally having my first "major" issue.  I took the boat ('99 Sunsetter VLX) out a few weeks ago for the first time in several months.  It took a little longer to start than normal (maybe 4+ seconds of cranking), but nothing to be concerned about with a cold engine.  However, the transition from idle to into gear was extremely rough and would practically kill the engine unless I gave it a decent amount of throttle.  This has never happened before, but it eventually went away once the engine was warm, so I thought little of it.  Fast forward to the very end of the day (after 6+ hours of normal use with no other issues), and my wife is surfing (5 passengers, ~2000 lbs. ballast), and the boat won't accelerate over 10 mph.  The engine bogs down, surging back and forth at low speed, the throttle has no response past a certain point, and we even got a couple backfires and a little smoke.  Immediately trailer it and go home.

The symptoms seem like a much more severe version of a problem that I had a few years ago with water in the fuel, so I swap the low pressure fuel filter (high pressure was replaced a couple of years ago), and add a bunch of water removing chemicals.

Took it out yesterday, and it started right up and ran normally up to 30 mph, then the same bogging down/surging/no throttle response issues emerged.  Topped out at 35 mph (normal top speed is 45 mph).  Weighed the boat down with the same 2000 pounds of ballast (only 3 passengers this time), and it was fine at surf and wakeboard speeds, but still bogged down over 30 mph.

The only thing that I can think of is a failing fuel pump and cylinders not firing under heavy load.  Does that seem likely?  Thanks in advance for any insight you can provide!

Unrelated: Are these the correct spark plug wires for my engine? 

https://www.skidim.com/prodinfo.asp?number=RK120017

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justgary

The best way to isolate your problem is with a fuel pressure gauge.  Check the pressure with key on, engine off, then at idle, then at cruise, then at wide open throttle.  If your pressure stays in the neighborhood of 42 PSI the whole time, it isn't fuel delivery.

Those wires should work.  You can also get them from your local auto parts house.  Change the cap and rotor while you are at it.  I bought a cap a few years ago that had an extra tab at the bottom that I filed away to make it fit properly.  Get one with brass points instead of aluminum.

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Bozboat

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SkiPablo

my thoughts are check fuel pump and also plug wires and distributor like mentioned.     As for the correct wires, just email SkiDim - they will respond that day with the correct part number

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aggie08

Thanks guys! I forgot to mention that I swapped the cap and rotor when I replaced the LP filter just for the heck of it. 

I'll see if maybe there's some build up in the HP filter, then do a fuel pressure check. I feel like the fuel pump squeals have gotten louder and longer at key turn recently (may be psychosomatic) so seems like a likely culprit.

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BlindSquirrel

Yeah, there should be no fuel pump squeal/ high pitch noise when the engine is running. You should hear it prime when you turn on the key, but that's it. We had that issue a while back, turned out to be the inside of the fuel line collapsed restricting flow. New fuel line from the tank to the filter to the pump and the she stopped squealing. We had similar performance issues that you do, but worse.

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williemon

I had a similar issue end of last year. I had been through this before as well. I replaced fuel pump again as well as fuel line between pump outlet and high pressure filter. I found the hose had a bubble inside it but I replaced the fuel pump anyway so not sure which one cured issue. Ran like a champ all this past season. 

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