Mercury Jet Sport cavitation??

[ealoysiusc]

Hi! I've got a '97 SeaRayder with 120 hp mercury jet sport engine. It starts and runs fine until it gets close to being on plane...the engine struggles and I get no where. Here's what I've done so far...testing after each step with no resulting improvement.

Cleaned fuel filter screen and replaced in line filter
Thoroughly cleaned the two carbs
Replaced spark plugs
Compression check (150 lbs in each)
Spark...all four good spark
Replaced ride plate, gasket and screws
Impeller clearance 22 to 25,000
Inspected wear ring...no grooves or excessive wear noted
Inspected impeller...all blades look good...no dings or chips

I am lost. My mechanic friend suspected exhaust leakage into pump, but I can't see how that could be so since from intake grate to exit nozzle is a closed system. I guessed the high speed portion of the stator was bad, but he says it won't run if the stator is bad. I have the service manual but found no help there. Any help....advice would be greatly appreciated. My email address is ed_pam@bellsouth.net. That is "ed underscore pam"Thanks in advance. ED

 

[ealoysiusc]

Re: Mercury Jet Sport cavitation??

I got a lot of views but no replies and was about to give up. Then it hit me. I thought that the reverse gate could be obstructing flow through the jet pump. I tied it up with a bungie cord and voila my problem was solved.

Now all I've got to figure out is how to set up the reverse gate so it doesn't obstruct flow.

Hope this saves someone else some time and money.

 

[QuadManiac]

Re: Mercury Jet Sport cavitation??

Good job in the diagnosis. Guess there aren't a lot of 'jetters' here, ergo lotsa views, no opinions, lol.

 

[ealoysiusc]

Re: Mercury Jet Sport cavitation??

Thanks for your thoughts. If there are so few of us we need to stick together. Suprising that these Marinas are so lacking in experience with these jet boats. Mostly I tinker with Jet skis......Yamaha, KZ and the dreaded SeaDoo. Let me know if I can be of any help....you have my email in my first post. ED