Problems with hammerhead 375 engine...

[Julian3342]

Hello,

I have a Malibu barefoot boat 2003 with the Hammerhead 375 engine. When the engine is cold and I start the boat, it runs normally even under full and partial load. As soon as you drive for a longer period of time at a higher load and ease off the accelerator, the engine stops and is difficult to start. Our mechanic can't find the problem either.

[csleaver]

Hard warm starting can be caused by over fueling due to improper sensor data from the Engine Coolant Temperature sensor or from leaking injectors.  I've also experienced internal swelling of worn fuel lines cause hard starting or stalling after the engine was running for more than 30 minutes. 

[justgary]

8 hours ago, csleaver said:

internal swelling of worn fuel lines

Wow, what a pain to diagnose that one!  At some point, I guess you just shrug and plumb in a six gallon tank to see what happens.

I'll add the spark module under the distributor cap to your list.  Sometimes they just don't play well when they get warm.

[csleaver]

It was definitely a strange situation.  The complaint was that the boat would start and run fine when launched, but after 45 minutes the engine would stall, then crank-no-start, and they got towed in.  The next day their boat would start and run again for 45 minutes, until the same problem occurred.  I ran it on a flush hose, and sure enough, the engine stalled and would not restart after 45 minutes.  The fuel supply hose from the fuel tank looked like it was completely clogged with rubber debris.  The hose was replaced, but the old hose was still on my workbench the next morning.  The inside of the old hose looked to be in perfect condition again after 24 hours.  Very weird. 

[Steve B.]

Wow csleaver ! 

[csleaver]

It's still all just verifying the basic things that the engine needs to start and run.  Proper cylinder compression, correct fuel pressure and mixture, ignition spark at the right time.  Most running issues are caused by a problem with at least one of those things.

[Bozboat]

1 hour ago, csleaver said:

It was definitely a strange situation.  The complaint was that the boat would start and run fine when launched, but after 45 minutes the engine would stall, then crank-no-start, and they got towed in.  The next day their boat would start and run again for 45 minutes, until the same problem occurred.  I ran it on a flush hose, and sure enough, the engine stalled and would not restart after 45 minutes.  The fuel supply hose from the fuel tank looked like it was completely clogged with rubber debris.  The hose was replaced, but the old hose was still on my workbench the next morning.  The inside of the old hose looked to be in perfect condition again after 24 hours.  Very weird. 

 

52 minutes ago, Steve B. said:

Wow csleaver ! 

This is what I love about this forum, being able to learn about stuff like 45 min expanding fuel lines, temperamental ICMs, and fuel hammer.  @csleaver how often should fuel lines be replaced? 

Edited May 1 by Bozboat

[csleaver]

There are many things that can affect the lifespan of fuel lines.  Exposure to UV, ethanol, or other chemicals is a factor.  The consensus tends to be somewhere around 10-15 years max for replacement, but anything that is visibility weathered, cracked, damaged, or abnormally stiff/soft should be replaced.  The quality and manufacturer might also make a difference.  It may not be a coincidence that the failed fuel line I replaced had "Made in Malaysia" printed on it.