low compression

[seadooflorida]

I have a 2000 sea doo gtx millennium edition and I did a compression check and it come to 100 psi on both. So I removed the cylinder head it had some white chalk like power in the cylinder head in a vent that lead to a hose going to the back of the ski. I've never seen this, the ski was used buy the previse owner in salt water. I thinking its salt deposit and this is why the cylinders failed.

 

[SabrToothSqrl]

I assume the ski also didn't run properly, which lead to the compression test?

I'd hate to tear down a working engine just because some gauge said so.

And yes, those are salt deposits, when you run salt water through a heated environment (engine) it clings to the metal parts.

Also, if you don't drain/flush said salt water, it will build up clogging the cooling system.

I'm not a fan of running anything in salt water. It's fun, but it's murder on the skis.

Newer skis are closed loop cooling. They use the ride plate so no salt water even gets anywhere except the open loop cooled exhaust.

 

[Minnetonka4me]

Your description sounds normal...if that crust is just in the cooling jackets and not in the combustion area...that is normal. Hell, even in freshwater we see some mineral deposits.

Do you know your compression tester is right on? also if the tester end isnt the exact same length as the spark plug it will cause lower readings.

I think 951s have 130 normally...? Im blanking. Sabr knows...

 

[seadooflorida]

I assume the ski also didn't run properly, which lead to the compression test?

I'd hate to tear down a working engine just because some gauge said so.

And yes, those are salt deposits, when you run salt water through a heated environment (engine) it clings to the metal parts.

Also, if you don't drain/flush said salt water, it will build up clogging the cooling system.

I'm not a fan of running anything in salt water. It's fun, but it's murder on the skis.

Newer skis are closed loop cooling. They use the ride plate so no salt water even gets anywhere except the open loop cooled exhaust.

The last owner beat this ski up. I've replaces fuel lines, oil tank, rebuild the carb, fuel baffle. It started up with no problems except it was blowing white smoke. So I did a compression test and found it had low compression. I don't know how long the ski has been sitting, last registration sticker is 09. With the ski blowing white smoke and low compression isn't that a sign of bad piston rings. With the head off the pistons look good and sleeve are smooth and I don't feel any nicks. Pistons move threw the sleeve smooth and not a lot of play with the pistons.

 

[wolfie]

white smoke could also mean water. could have a gasket failure from sitting so long. what do your spark plugs look like?

 

[kicker]

Can you look through the exhaust ports and see the sides of the pistons? Do they look the same or different? If there is "blow by" usually the top inch just below the rings will be almost black, from the blowby being charred on the side of the piston.

 

[seadooflorida]

Can you look through the exhaust ports and see the sides of the pistons? Do they look the same or different? If there is "blow by" usually the top inch just below the rings will be almost black, from the blowby being charred on the side of the piston.

I took the rav values out and looked down at the side of the pistons. They don't look black, but both ravs were caked with heavy oil and one was stuck. Will this effect the compression test. The compression tester is new and I put it on hand tight to do the test. When I first ran the engine I didn't run water threw, I only ran the engine for a few seconds because it was blowing the white smoke.

 

[AdamXP800]

The white smoke wouldn't concern me that much. Mine smokes like crazy when I first fire it up from burning off the fogging oil


Long live the 2 stroke Seadoo!

 

[AdamXP800]

With the compression numbers being dead even on both cylinders you should try a new gauge. You could be chasing a ghost here


Long live the 2 stroke Seadoo!

 

[jammin777]

while doing the compression test, did you hold the throttle wide open? it make a difference. someone will reply about the raves weather it will effect the compression or not.
:agree:agreed with Adam, may be fogging oil burning off

 

[AdamXP800]

I've heard if they are stuck open it could give a lower reading. I'm not 100% sure on the credibility of this statement though. Someone else will chime in


Long live the 2 stroke Seadoo!

 

[Minnetonka4me]

Raves shouldn't matter you can do a compression test with them removed and it will not affect it.

If the Pistons aren't heavily scuffed or battered on top I would say it's your tester. Have you tested other machines to get a feel for how accurate it is?

Sent from my SGH-T989 using Tapatalk

 

[Sportster-2001-951C-Stock]

My bet is your gauge is wrong! Buyer beware note: The schraeder check valve location must be in the plug hole threaded fitting that threads into the cylinder head as close to the piston as physically possible and not at the gauge head, I've heard some of the cheapo compression gauges may be incorrectly configured so beware of this possibility, maybe you can correct this issue easily yourself, IDNK!

If both cylinders are the same but lower or higher than expected, it's a huge tell that your gauge is FUBAR. I've had my same gauge for decades and I'm really careful not to drop or contaminate it, but if your gauge is new and untested, it could read almost anything! ie: never fully trust a new unproven gauge accuracy unless the reading is as expected.

Remember to properly flush with fresh water following each ride in salt, to reduce mineral deposits and corrosion to a minimum. If you do already, then you done good.

I've measured my 951 twice now since I bought this boat two years ago, this carbed 2001 951 blows 135psi on a good day(the day I bought it) and 120psi stone cold after setting for at least a week (I guess the oil runs off cylinder walls, or my motor has gotten weak). Runs great still!

Good luck to you all and have a great day!

 

[SabrToothSqrl]

The white smoke could also indicate someone used the wrong oil, but at this point it's moot.

Send the engine to a shop that will give you a no fault warranty to have it rebuilt.

I've seen compressions from 100-130 run just fine. I check RPM at WOT ON THE WATER. Which, for a 951 should be as close to 7k as you can.

For the large 951, the compression difference between pistons is more important than the actual reading.

I would have maybe taken it for a ride before popping the top, but like I said, let's not worry now.

It sounds like this ski has had a rough life, the 951 isn't a really garage rebuilder friendly engine... I always use a shop that backs up their product.

We are all also assuming this is a carb 951 ski, can you confirm that?

Thanks.

 

[seadooflorida]

Yes its a carb 951 ski, I think ill put the top back on and get a different compression tester to see if I get a different reading.

 

[SabrToothSqrl]

you will have to install a new head gasket to do that.

I would install a new gasket, reinstall head, check compression, and if it's reasonable, go for a ride.

seriously. running on land doesn't tell you anything.