2002 Speedster with 240 Merc M2 - erratic RPM

[Speedst-err?]

So I have the 2002 Speedster with the 240 Merc. I was out yesterday for probably the longest run since I've owned the boat - 3 years. I spent a lot of time at just above idle cruising and so I suspect this is the main reason for my problems as I have noticed in the past the boat doesn't really like to putter along. I have also noticed when trying multiple times to get an inexperienced skier out of the water I would have to take the boat for a run to open it up because the engine would start to sputter but this would normally get it running smoothly again. Yesterday was very different though. When I decided it was enough puttering, I opened up the throttle and I wasn't on plane very long and it started to act up. RPM would drop as if I pulled back on the throttle (but hadn't) and then it would try to regain RPM but not fully recover. It would do this a few times so I backed the throttle off but it never stalled. At idle it sounded rough so I tried a few times to reverse the engine thinking I had something caught in/on the intake. The first few times this seemed to correct the issue and it would run smooth for a minute or so but then start to act up. I was about 10-20 minutes from the launch but finally managed to hobble my way back. I was able to shut the engine and but towards the end I never got it to run smoothly. I took a quick look at the inlet and outlet and doesn't seem like there is anything in there. It felt more like an ignition or fuel delivery issue. I haven't had time to look at it yet, just to check the forum and when looking its a bit like WebMD - the symptoms could be simple cold or something terminal but it sound a bit like what Big Tom was experiencing in his post:

Sea Doo x-20 w 2002 Mercury 240 EFI M2 Jet Drive Engine Problems​

Any leads would be appreciated.

 

[M3Man03]

When you had to run it to "open it up" - did you notice a lot of smoke? If so, I'd say something's off with your oil injection system.

If you didn't notice any additional smoke, I would say to focus on the fuel system. Do what I did, remove the vapor separator tank and clean it all out. Replace the fuel filter and make sure that your lift pump is working correctly.

 

[Speedst-err?]

Yes, I would say it smokes more than I would have expected after the start/stops when skiing and also when cruising just above idle. Also yesterday it seemed to be producing lots of smoke after the problem developed. It always smokes a fair bit on initial start up but when running it at higher speeds that hasn't been an issue. Thanks for taking the time to reply.

 

[Tim75]

Yes, I would say it smokes more than I would have expected after the start/stops when skiing and also when cruising just above idle. Also yesterday it seemed to be producing lots of smoke after the problem developed. It always smokes a fair bit on initial start up but when running it at higher speeds that hasn't been an issue. Thanks for taking the time to reply.

It's never a fun time, but it is time to check all your bleed system hoses. Those are the small black hoses that run around the engine, close to the block. The hoses get brittle over the years and the ends split. Can cause many different issues. Have you ever had the injectors out and serviced on a flow bench? Costs about $25 each. A leaking or stuck open injector(s) can cause some of your problems. Don't bother with "miracle" injector cleaners. They don't work and can be damaging.

Have you checked your fuel pressure? Should be 36psi.

If you decide to clean out the vst, order the molded o-ring before you start. About $22. There is another fuel filter in there that should be able to carefully clean. When you reconnect the wires on the vst pump, make sure you have the correct polarity.

What is your max rpm at WOT?

 

[Speedst-err?]

Thanks Tim75. I'll check the bleed hoses and no, never had injectors cleaned since I've owned the boat.

Also haven't checked the fuel pressure. RPM and Speedo gauges went down end of last season so I don't can answer that one. I was out the week before last pulling skiers and had no issues whatsoever during that outing. Boat hummed along just great.