Low compression both engines 2nd cylinder

[Stalt]

I just had a compression test on my 2007 Sx and I was told both 2nd cylinders were at 100 compression and the others at 160. I noticed the boat bogging down last summer. What does this mean? Do I need new motors? What would be the average price. The mechanic told me I was better off to ride the boat easy for the summer and have them worked on late fall.

 

[ncnmra]

Was the compression checked after the engines had warmed up properly? I made the mistake of testing compression on cold engines, and I think I initially had similar numbers. After a proper warmup, the numbers were fine. Make sure you check with a warm engine.

 

[Scottintexas]

glad to have you on board,

have you dealt with this mechanic before?
Is the mechanic a Yamaha dealer, PWC facility, other general boat facility or car mechanic?

If you have a small amount of mechanical skill you can check the compression yourself or I would recommend going to another place, even a PWC shop since these are the same engines as jetskis and get a second opinion,

be sure to check out the known issues link in my sig. below and the FAQ tab at the top of the page for lots of great info,



.

 

[Gym]

Previous advice is good info. Low compression usually indicates one if two things. warn piston rings or leaky/burned valves. If as previously stated if your cylinders have low compression on warmed engines you can squirt a couple shots of engine oil into to the spark plug hole of the low compression cylinder. If the compression in that cylinder increases substantially that indicates warn piston rings. If there is virtually no change that indicates the valves are probably carboned up and are not seating properly causing the compression to leak out.

I suspect it's most likely valves which would be the least costly of the two scenarios. It would require removing the engine head only and replacing or cleaning and lapping the valve to the head for a better seal.

If you do find it's carbon buildup on the valves you may want to start adding Yamaha Ring Free to each gas fill up to help reduce carbon build up.

 

[Stalt]

Thank you for the info. Much appreciated.