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My jet boat is making a 'putting' noise when trying to accelerate.

You can find all details regarding my boat here: My Boat Info

The noise seems to happen in the mid-rpm range; 4,000 - 4,800 RPMS, below 4,000 it sounds fine and above 5,000 it stops ( this boat idles at 1,250 and shouldn't be run greater than 6,500 )

My father thinks the engine may be misfiring, but I think the issue may be cavitation.

Here is why I think it may be cavitation:

  1. My engine is directly below my steering column, but the noise seems to be coming from the back of the boat at the jet pump... I would think the sound would be coming directly from the engine?
  2. The impeller clearly has a few nicks... I intend to replace this regardless of the what the actual problem is.

The best way I can think to test this for sure is to run it on land... if I still get my 'putting' noise, it obviously isn't a cavitation issue. I have a flush kit installed already, but I haven't tried accelerating using it, can I safely get to 4,500 RPMs with my flush kit?

If it turns out it isn't cavitation, how do determine the cause of the misfire?

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  • Those jet engines use water to cool themselves. I'd check with a shop to see just how high (in rpm's) you can run those things when they're dry. I never dared run my jet ski for more than 10 seconds, with only a few quick bursts over 3k.
    – Lynn Crumbling
    Commented Jul 18, 2016 at 15:26
  • I doubt about a misfire. Normally misfire appears at lower revs, and on higher revs it works better. Is it on constant revs or on acceleration? Can you please make a video or sound record somehow?
    – Arturs Bolsunovskis
    Commented Jul 18, 2016 at 15:45
  • @Lynn Thats what the "Flush Kit" is for ( atleast thats what I think there called ). I can plug my garden hose right into the flush kit to supply water to cool the engine.
    – Calvin
    Commented Jul 18, 2016 at 15:45
  • @ArtursBolsunovskis, I video recorded it with my phone yesterday, but it is impossible to hear the 'putting' over the engine / wind. I will try again next time I start her up.
    – Calvin
    Commented Jul 18, 2016 at 15:50
  • @Calvin Yep, I'm familiar with the flush kits. You had asked in the question whether you could safely rev up to 4500 rpm with the flush kit -- I was just saying that I'd make a call to a Boston Whaler mechanic, and ask them.
    – Lynn Crumbling
    Commented Jul 18, 2016 at 18:26

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