Rxp low compression

[paperman]

Does this sound right?
I took out my 2004 rxp for the first ride of the summer a month ago. After 10 mins of running just fine, it started to stumble/ develope a miss fire. Had to return to the dock (running real bad, did not think I was going to make it back).
Got and started to look into what it could be. First, no warning lights came.
Changed the plugs . Could not figure what was causing it.
So I took it to the sea doo dealer , figured they are the pros and know everything . Well after having it for 2 weeks (I stopped by several times to check to see how it was coming along) this is what they found. All three cylinders had low compression, all in the 120s range. Would low compression really cause a miss fire all the sudden. I know could be many more possible things but did not thing low compression would be one. Does this sound peasable.

 

[AircraftDoc]

The compression is set at 140 psi for supercharged and 180 psi for normal.
Their have been discussions here at this forum. Use the search bar at the right upper corner. Low compression. I don't remember what is the lowest number that it can be.

I would have started with fresh fuel with fuel stabilizer. Then spark plugs. I would do your own compression check and spray some oil into the cylinder first, then check. You could be ok.

 

[mikidymac]

Don't spray oil in the cylinders for a compression check as it will give you a false high reading.

 

[AircraftDoc]

Yes, spray the cylinder with oil.
You want to find out if the rings are leaking or the valves.
Also, do the compression check after a 1 to 2 minute engine run so it's warm and the engine has normally oiled the cylinder. You will get a more accurate reading. Low compression will lower you power output, but not overall running.
Sometime just changing the oil will help with the valves and compression if it is time. Oil can mess thing up when it breaks down.

 

[paperman]

So if I spray oil into the cylinders, does this tell me the rings are leaking?

 

[paperman]

Also where can I buy the right size compression hose fitting. My snap on set is the wrong size.

 

[AircraftDoc]

Also where can I buy the right size compression hose fitting. My snap on set is the wrong size.

I had to borrow one from a mechanic with a Macco compression kit. I got lucky. I found someone to let me use their tool. Left a ten in his kit when I returned it. Maybe try AutoZone, they have a free tool loan system.

 

[AircraftDoc]

So if I spray oil into the cylinders, does this tell me the rings are leaking?

If you get a high reading - 135 to 140 psi, then you know the rings are leaking. If you still get a low reading, then the valves or head gasket is leaking.
How many hours? Last time oil change?

Could have just had some water in the fuel that finally floated into the system. SeaFoam would help break that up and clean it out.

 

[paperman]

New update. Just got ski back from dealer. Was told the Compression is 110,115 and 135
The guy on the phone earlier told me something different. So they said it need a new motor $4200. So I told them no, on the new motor.
Fast forward now.
Took the ski out for a ride today and it seems to run just fine. Hitting 8200 rpm and hole shot is strong. Top end is around 70. Running good for now
Will it run with the low compression. I did notice they took all the old fuel out of the tank. I put in some high octane before my test ride.
Probably still need to do a compression test my self.
160 hrs on the machine
New oil change

 

[AircraftDoc]

Great news.
I had a 68 F100 with a 360 that ran on propane. Since it ran on propane it ran even when it had very low compression. You could hear the piston slap around. Not much power and you had to keep the rpm's down, but it ran like a clock.
I have seen posts telling that these engines run into 600 to 800 hours.
I think you had some water or other crap in the fuel system. I bet your compression gets a little bit better.

 

[Hawk388]

Great news.
I had a 68 F100 with a 360 that ran on propane. Since it ran on propane it ran even when it had very low compression. You could hear the piston slap around. Not much power and you had to keep the rpm's down, but it ran like a clock.
I have seen posts telling that these engines run into 600 to 800 hours.
I think you had some water or other crap in the fuel system. I bet your compression gets a little bit better.

I'm betting it does as well.

Now that it's running good, it tells me the old fuel was the culprit. You likely had some water in the tank which will cause the stumbling you described. Before you put these things up for the winter, ride it to lower the fuel level on the gauge a bar or two. Put fuel stabilizer in the tank, then fill the tank as high as possible. This will mix the fuel and stabilizer really well. This will prevent condensation from forming.

 

[XP 787]

Even though its running fine do your own compression check for piece of mind.

 

[Thepaperman]

Well I verified the compression last weekend. 2 cylinders are around 110 and the other is 135. Being the 2 low cylindersare next to each other, could it just be a head gasket? Really hate to tear it apart when for now it is running good.

 

[mkov608]

Yes that could be a head gasket problem. If you want to isolate the location of your leak, you need to perform a leak-down test. OBTW, if you do suspect a head gasket leak, don't continue to ride the ski; delaying the repair will most certainly cost you more later.

 

[Digdog]

Take the hose off of the intercooler on the side that goes to the intake and see if there is water inside

 

[Thepaperman]

Digdog, you win the prize ! There sure was water in the intercooler. Took it out and did a pressure test on it . It did not take long to show signs of it leaking .
Was lucky to find one for sale close to home. Already have it installed and it's running great. As good as it feels to have her running, I still will need to deal the the 2 cylinders that have low compression. Winter project. Going to start with hoping it's a head gasket.

 

[Digdog]

Do a compression test after the season and see where the cylinders are at before you take it apart, they may come back a little, or at least to where they are all the same, then you can just leave it be and run it. Let us know what happens, glad to hear it's running. Remember to winterize that cooler properly.

 

[ski-d00]

If your dealer is telling you that you need a new engine because the compression is 110 then you need to get a new dealer. I've seen quite a few sc skis with 110 psi and they run fine. A leak down test is a better test for a 4 stroke for engine health. I wouldn't change anything, just ride it.

 

[Thepaperman]

That's my plan.just ride it till the end of the season. Then I will do anther compression test including a leak down test.
Thank for all your help.

 

[ricardo1]

Did you ever do the leak down and compression test before you stored it?

 

[Thepaperman]

I have been so busy this fall that I have not done another compression test or winterize it yet. I know this is bad for it is getting cold here in the north. Maybe next week I can get this done. Ricardo , thanks for the reminder to get this done.