1992 GTX and 1993 GTX speed issues

[chipnbud]

Hi Group,
I have a 92 GTX and a 93 GTX that are bascially stock with no modications. I was led to beleive when I bought them last summer they had a top speed around 50- 55 MPH. Much to my wifes disappointment and Mine as well running full throttle on glass smooth water using a GPS device top speed is 38-39 MPH. I have replaced the props and the wear rings have .020 - .035" of clearance between the blades and the ring on both units.
The engines are running great and the rev limiter on each engine seems to hit about 6600 rpm top end.
The intake grates are original and in good condition.
I would appreciate any help you or advice guys could give. I would really like to get both skis to run about 50 MPH or faster if possible.
Thanks in advance
Chip Smith.

 

[kustomkarl]

Welcome to the seadoo forum Chip. I would check the compression first so you know what is going on internally. I believe that those seadoos should run about high 40's. Here is some information to do a compression test properly. You'll need a compression tester. Go to Auto Zone. I think they sell for like $25.00. The compression gage, will screw in the cylinder head in place of the spark plugs. To test compression, remove both spark plugs. Place spark plug caps on the plug cap studs near the cylinder head to ground the empty caps. This completes the circuit of the ignition electrical system and prevents any electrical problems from the caps being un grounded. Using the correct adapter for the threaded end of the tester,( same length of the spark plug threads length)screw in the tester in one plug hole. Hold the throttle wide open. Push the start button. Watch the compression gauge, when it peaks out at the most compression, let go the start button. Read the psi number. I would do it 3 times to be sure it is accurate. Check both cylinders the same way. The ideal compression is 150 psi per cylinder. If it is less, it's not a problem as long as they are close to being the same. If the psi is less than 90 it might need be time for a tear down and a rebuild. If the psi in 1 cylinder is say 140 psi and the other is 80 psi you need to tear down and repair. This difference is a lot then there is a problem. I hope this helps you.

Karl