Compression loss

[extra300]

on my 99 gtx limited, 130hp.947 engine.. always took in for winterizations, they have said in the past 6 or so years that the compression was always 145-150, this last year they said it dropped 40 psi per cylinder down to 110, which in fact it did,i double checked....i got shop manuel on the way..,,but can someone tell me what the standard compression should be...and if it is around 145-150...any ideas on where to start lookin, ive heard and been told that it might be more than pistons and rings,,,oh yeah,,,it starts good and always has,sounds good, performance is off a little out of the hole,,but top speed still right up there....any help would or ideas would be greatly appreciated.....thanks...

 

[kustomkarl]

The preferred psi per cylinder is 150 psi. It isn't the idea of the number, but the idea that all the cylinders are with in psi of each other. You don't want like 110 in one cylinder and 150 in another. if all the cylinders are 120psi than than that is ok and not a bad thing. Anything less than 90 psi is time for a rebuild. If you have any other questions give us shout. there are many active members here eager to help, and respond.

Karl

 

[scooper77515]

That is a 10-yr old motor...

...if you have run it hard for 10 years, it just might be starting to wear out.

Might be time for new rings and a hone-job.

Of course, my experience is mostly car-related, so it might be different for sea-doos...:driving:

 

[kustomkarl]

How many hours are on the machine?

 

[extra300]

210 hours,,and it is 110 per cylinder they are the same,,but wondered why the sudden drop and if i should go with new pistons and rings...thanks...

 

[kustomkarl]

You might not need pistons but a good hone and rings. The only way to tell is take the heads off and measure the bore of the cylinders and check the condition of the cylinders. It still isn't that bad, I would go maybe another season.

Karl

 

[extra300]

thanks for all the advice and the input, thought mayb 110 was horrible but maybe not......thanks all...

 

[kustomkarl]

If you have any other questins we'll be here to help you out.

Karl

 

[scooper77515]

How do you tell how many hours are on an engine? Is there a gauge somewhere that I don't know about?

 

[kustomkarl]

Scott that info is stored in the mpem. You need a Programmer to get that information, that only the seadoo dealers have.

Karl

 

[extra300]

it does have a 16 function information center gauge,,,and hours is one of the functions...dont know how accurate it is...but it reads somewhere around 210

 

[kustomkarl]

The mpem (Multi Purpose Electronic Module) keeps all info on the history of the seadoo including the hours of use.

Karl

 

[derek]

you double checked the compression yourself?

 

[extra300]

I did double check it myself, and it is at 110 in both cylinders after about 3 revolutions..

 

[derek]

then run it. and over the winter, when parts get cheap again, buy a spare set of jugs and get them punched out.