240HP excesive smoke, low rpm

[time2see]

Hi
Hope someone can help here.
I purchased a 2001 Challenger 1800 240hp.
It has not run for a while and we tested it yesterday.
Excessive smoke in the water until full throttle but ran well, then after about 1/2 hour, revs dropped right down and plumes of smoke came out.
Seems like it may have fouled the plugs (todays job, pull plugs out)
Could this be getting to much oil?
What else do I need to check over as I am a newbie to the Seadoo/Mercury jet

 

[Dr Honda]

If it hasn't been run in a while... you need to check everything.

BUT... the RPM's dropping, and a lot of smoke coming out doesn't sound good. Personally, I would check the compression. You may have lost a cyl. You are looking for 125 to 135 psi.