1995 sport jet 90, only 4000 RPM

Hello out there, i have recently purchased a 1995 Tracker pro jet 18, with a 90 hp jet inboard/outboard. runs fine. except only about 20mph. and only hits about 4000 Rpms. but yesterday it jumped to 5000 Rpm almost jumped out of the water doing over 30mph which is what i was told is about Factory , but only did this for about 30 seconds and then back to about 4100 Rpm and was doing a slight surge, . I am not used to jet motors being from so. illinois . only propellers .but boat is in good shape and starts everytime. and paid 3000 dollars so i could not pass it up. would anyone be able to help me on what i have got or at least where to start. Is one cylinder not producing. are the carbs not timed together or is the throttle linkage just not adjusted all the way . Note: before we bought it The fishin hole in st louis rebuilt the Carburaters. any help is good help

probably a restriction in the fuel line...quickest way is to borrow an outboard can and substitute it for the onboard tank.

you are better off diagnosing the issue than guessing...also, changing one thing at a time and noting it, is a much more efficient approach

Sounds like mine, Here is what I have found on my motor. Top piston rings seized in the ring grooves. Second time I have been through this with mine. I would suggest removing exhaust manifold to look at the side of the piston. Both times most of the damage was on the exhaust side of the piston. I would also suggest bypassing the oil injection system and mixing fuel and oil in the tank.

That is a Chrysler / Force powerhead sold by Brunswick as a Mercury Sportjet.---------Run with a timing light to see if you can pinpoint ignition problems on one or more cylinders.--Try having someone operate the primer bulb to see if it is a fuel supply issue.-------These machines were popular for about 4/5 years and are now basically orphans with little or no factory parts support.