787 engine blown (98’ challenger 1800)

[MH jefe]

I recently bought a 1998 seadoo challenger 1800 from a private seller. He swore up and down there were absolutely no problems.. when I went to pick it up, he started both engines for about 10 seconds saying he didn’t like them on out of water.. he refused to take it out the lake but promised if I had any problems i could take it back for a refund. We shook on it, I took the boat home and tested it on the lake next day.. both engines wouldn’t start. I used a booster and they started but the port side engine kept shutting down at idle... I also heard a back fire sound coming from that engine... I took it to get checked out, and was told the rear cylinder was reading 0psi and the other was 140psi. It needs either a top or full rebuild.
Does anyone have any suggestions on what could be the cause and possible solutions(what could cause a cylinder to fail)? Also do I need to work on the carbs at all?
Where can I get a step by step guide to remove the engine?
Thanks in advance

 

[burtshaver2021]

So to answer your questions you can find a step by step guide to removing the engine in the shop manual, available on this site with a premium membership, check first just to be sure, but I’m pretty sure I got the manual for my 98 Challenger on here.
Don’t use a booster on these or any pwc, don’t boost from a running vehicle either, ok to boost from a vehicle if it’s not running.
The low or non existant compression in the one cylinder could be from a number of things, running lean due to an air leak in the fuel system, carb gasket or outer oil seals or could be a lack of oil going to that cylinder, you will need to take it apart, do a leak down test before you disassemble the engine to determine if there are any air leaks, go through the fuel system, check the oring on the fuel filter/ water seperator. Rebuild the carbs.
Hopefully you didn’t pay water ready price, myself, if the seller won’t let me water test it, then I assume that there are issues and pay accordingly. If I were you, I would go back to him with your handshake guarantee