Just Curious

[FlyinFred]

I own a 1997 XP (787) and 1998 XP Limited (951). They have been running great until recently. The 97 XP would barely start on the trailer and the 98 XP Limited would run on the trailer just fine, run in the water and then fall on its face once it ran for about 15 minutes. I did a compression test (thank you Seadoo Forum for the lesson in that) and got.
97 XP, 85 PSI in both cylinders. 98 XP limited 90 PSI in both cylinders.
I totally understand that its time for an engine rebuild or replace. I'm curious why my 98 XP Limited would run great at that PSI and then fall on its face and not start again until the next day.
Would the compression drop more once the ski warmed up because the cylinders expanded. .Just curious.
Thank you all and I pray your upcoming season is fun.

 

[noviceskier]

How do the plugs look, color? When I first tried starting my HX with old plugs that came from a running ski, it wouldn't run. Swapped out with new BR8ES plugs and it's been running good for me since. Is the gauge on your compression accurate at all? Where'd you buy it?

 

[FlyinFred]

How do the plugs look, color? When I first tried starting my HX with old plugs that came from a running ski, it wouldn't run. Swapped out with new BR8ES plugs and it's been running good for me since. Is the gauge on your compression accurate at all? Where'd you buy it?

The plugs look good. A bit black but good. I use only BR8ES and swap them every day. I bought the compression gauge set off of ebay and then had gauge calibrated. It is off by 5 PSI and that is as close as it could be adjusted.

 

[mikidymac]

Get a different compression tester. Make sure the battery is strong and the throttle is held wide open when checking compression.

My suspicion is your tester is bad as numbers that low it typically will not even start when under the load of water.

 

[FlyinFred]

Get a different compression tester. Make sure the battery is strong and the throttle is held wide open when checking compression.

My suspicion is your tester is bad as numbers that low it typically will not even start when under the load of water.

I will try a different gauge and tester and see what I get. Either way a rebuild is in order.

 

[AKnarrowback]

I'm not an expert on that generation of machine, but like was said, with numbers that low the machines should not even be running.

What I am hearing is that you have two motors with almost the same compression numbers and within each motor the numbers are the same in each cylinder.

I would suspect a bad compression tester so try to find another good one and recheck.

Make sure your battery is strong, not old and worn out, with good voltage. Remember a battery can show good voltage but not have any amp capacity to carry a load if it is aged/degraded inside. When you put a cranking load on a bad battery the voltage can drop very low causing other issues.

If the compression numbers are higher with another tester I would go right into the fuel system and check everything. Make sure all the vents are working with no blockages, fuel lines are good and not deteriorating inside, carbs are clean, do a pressure test to make sure you are not sucking air into the system. After 15 minutes did you open the gas cap and listen for air being sucked into the gas tank? How do the water seperators look?

Don't go spending big dollars on a motor yet.

 

[etemplet]

That compression gauge has cost many people engine work that was never needed. It does not determine all by itself the condition of an engine. I'm with the guys that say you may have a gauge or testing procedure issue. Rule that out and proceed with other tests.

 

[FlyinFred]

All, Thanks for the advice.
Batteries load tested fine and voltage is good.
I have a new gauge that I know is dead on as it was calibrated a little while ago and it reads by 1 psi increments.
More updates to come.