Sea-Doo RX 2003 – Exhaust manifold bolts broken, strong vibrations – causes?”

[Felixniem]

Hi everyone,

last year I bought a 2003 Sea-Doo RX and completely rebuilt the engine over the winter.
During the break-in I was very careful:

• for the first ~3 hours only up to 30% throttle, always varying,
• then another ~4 hours with a maximum of 75% RPM, also with strong variations.

After about 7 hours the engine suddenly shut off and I found water inside the hull.
When I looked for the cause, I discovered the following:

• The 3 bolts that fasten the two-part exhaust manifold (aluminum cast) to the cylinder had broken off.
• One stud with nut was still intact.
• Both side vibration dampers on the large manifold body as well as the damper on the second manifold (below the fuel injection pump) had vibrated loose.
• All bolts were installed with Loctite.

I also noticed that the broken bolts (manifold–cylinder) had been installed with helicoils.

My questions are:

• Why could this have happened?
• Did I do something wrong during reassembly?
• Why are there such strong vibrations, even though the engine itself runs well and shows no obvious issues?

I am not a jet ski expert, so I hope to get some constructive advice and experiences from you.

Thanks in advance!

 

[mikidymac]

It is typically from the rubber pipe bushings getting worn and amplifying the vibrations until the bolts break.
Get all new rubber isolators and sleeves for the entire pipe.

 

[Felixniem]

All right, thanks a lot for the tip! They are indeed quite old, but they all still looked okay. However, 20 years is probably too old for the rubber dampers…


Are the bolts supposed to be tightened with a specific torque?


We used the standard torque values for M6, M8, and M10.

 

[mikidymac]

Yes, torque and procedure are in the service manual.

2003 SeaDoo GTI, GTI LE, GTI LE RFI, GTX DI, XP DI, RX DI, LRV DI, GTX 4-TEC Shop Manual - FREE PDF Download!

 

[etemplet]

Alignment could be a problem.

The misalignment causes the engine to vibrate which breaks the engine mounts then with no engine mounts the exhaust system is the factory holding the engine in place and it is not designed to do that. Stress on the exhaust breaks the bolts. I'd check the alignment.

I'm a machinist by trade and aligned equipment every day. Few if any of these skis have a good alignment on the engine to the jet pump. I generally spend at least an hour doing the alignment and at times have taken much longer. It makes a BIG difference. Good Luck

Here is a picture of an alignment that shook the engine dang near apart and broke all of the engine mounts. I believe in finding the "root cause" of failures before I repair anything.

 

[etemplet]

You could have engine issues.... twisted crankshaft or a misaligned balance shaft making the engine vibrate.