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Songbird

pulsating fuel injection rail

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Songbird

My name is Jay. I finally upgraded to a newer boat in June of 2016.  1999 Response LX.  Love the wake for slalom.  I still have my '82 MasterCraft stars and stripes.  Too hard to part with something I have had for nearly 28 years and had everything to do with meeting my wife of nearly 25 yrs.  Anyway, on to the reason why I am posting. 

 I noticed last week when I ran the boat on a garden hose to winterize that the driver side fuel rail had a noticeable throbbing or pulsating feel to the touch.  The passenger side was smooth no pulsating.  Is this an indication of a faulty injector or something else on that side of the engine?  Any feedback would be greatly appreciated.  Thanks in advance.  Jay Birdsong

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electricjohn

That is the side with the pressure regulator.  Also do you have steel or rubber crossover lines?  If steel you could be noticing what is called fuel hammer.

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Songbird

Thanks for the reply.  I should have noted that my boat has the Monsoon 325 engine.  I believe the crossover lines are steel.  Will have to verify next week when I will be where the boat is located.  Is fuel hammer considered normal? Thanks for any replies.  Jay

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Bozboat

If I remember correctly, symptoms of fuel hammer had more to do with rpms jumping around and being unable to maintain a certain rpm.  The solution was to replace the steel crossover hoses with rubber ones.   With what you describe, I wouldn't worry about anything until you see how it runs out on the water.

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electricjohn

Fuel hammer is not normal and Indmar makes a rubber crossover line kit to solve the problem.  Rubber acts like a cushion and absorbs the hammer.   The main issue happens at 2800-3000 rpm where the engine surges due to the fuel hammering in the fuel line when the injectors open, which they do 4 at a time.  This is called batch firing as opposed to sequential firing.  I still would nor rule out the regulator though.

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Engine Nut
On Monday, January 02, 2017 at 11:23 AM, electricjohn said:

Fuel hammer is not normal and Indmar makes a rubber crossover line kit to solve the problem.  Rubber acts like a cushion and absorbs the hammer.   The main issue happens at 2800-3000 rpm where the engine surges due to the fuel hammering in the fuel line when the injectors open, which they do 4 at a time.  This is called batch firing as opposed to sequential firing.  I still would nor rule out the regulator though.

Actually, the fuel hammer in a batch fire system happens when the injectors close and the fuel flow suddenly stops. Kind of like water hammer in an old house when the float valve in the toilet shuts the water off and the pipes clank. If you have steel crossover lines, you can verify fuel hammer by temporarily installing a fuel pressure gauge. The gauge acts as a dampener and absorbs the shockwave that occurs in the fuel system when the injectors close. If the fuel hammer causes surging at a particular RPM, installing P/N 786129 rubber centered crossover lines in place of the steel ones should help. If you don't experience the surging at the RPM where you normally operate the boat, I wouldn't do anything. There are lots of boats that have the potential to surge but the operator never experiences it because the boat does not get operated at the RPM where the surging occurs.

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Songbird

Thanks for all the replies.  This pulsating was at idle with the engine being operated on a garden hose.  I will have to check to see if it occurs at other RPM's when I get it out on the water.  I will post again when I have additional information.  Thanks again, Jay

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