Seadoo 717 hard start

[skrillac]

I went ahead and replaced the y fitting today. Pressure tested the carbs again with all the hoses in place (except the return). Pressure held fine.

Ski was hard to start on the trailer today. I probably cranked it for a solid minute or two, in 30 second intervals. Some of that time may have been getting fuel into the mostly dry carbs. Took the old plugs out and put paper towels over the head and spun it over to see if fuel was coming through. Towels had a small amount of gas on them, so it looked like I was getting fuel through. Put in new BR8ES plugs and spark testers so I could visually see spark. Spun it over 3-4 times 30 seconds. Would not start. Was finally able to get it to start by giving no choke and a bit more than 25% throttle. Ran it on the hose for 5 minutes or so while I tried my best to set low idle to 3000rpm.

It started at a pretty low rpm 2500ish then I revved it a couple times and it jumped up and then fell back down to around 3500ish. Thus began my back and forth attempts to adjust the idle. Turned it back out (left) a turn, revved it, then the rpms were too low again 2200ish. Turned it back up a bit (less than a turn), revved it, rpms were too high. Turned it back out a small amount, then I revved it, checked rpm again. Rpm was 3150. Revved it some more, 3200. Turned it back down a tiny amount, revved it under 3000. etc

I don't think I have addressed my issue with difficult starts. It seems that the issue is likely due to fuel delivery when I go to start the ski. Most likely carb-related. Gonna go try and put the ski in the water and then idle around for 30 minutes or so and come back and check plugs @burtshaver2021

 

[burtshaver2021]

I’m grasping at straws, not sure if this makes any since or not as I can’t recall anyone mentioning for sure exactly how they work but it seems you don’t have any fuel available when you go to start it. I’m wondering if the first Mylar disc on the fuel block , if it were leaking or if there was a hole in the grommet that holds it in place, if that would allow fuel to drain back out of the fuel block? Also when you were checking the 3 small holes in the carb throat, did you verify that carb cleaner was coming out of there? I know you said you seen it coming out the big hole for sure and out 2 of the small holes for sure, but was it coming out all 3 small holes?

 

[burtshaver2021]

Also where are you set at now for the low speed screw?

 

[skrillac]

Also where are you set at now for the low speed screw?

I took the ski out a few hours ago. Basically feels the same as it did before. Same throttle responsiveness, same speeds. I was at 1 turn out from closed on the low speed screw. This time I set both carbs to 1.25 turns out from closed. I also adjusted the throttle synchronization so that the throttle positions are a bit more in sync than before. I verified this with a bore camera. Both throttles open to the same positions roughly as observed from the naked eye.

When starting the ski, this time I've discovered that i just need to give it 25% throttle and it will usually start within 30 seconds. I started the ski that way on the water, verified 1400-1500rpm with tach (at launch my idle was 1400ish rpm. after punching it out of the no wake zone and idling back down, I got somewhere around 1500ish rpm). Drove it around for maybe 30 minutes to an hour. Let it sit for 15-20 minutes. Was able to start the ski the same way, 25% ish throttle.

So to recap:
Reset rotary valve timing to within +3-4 degrees of spec (tolerance is +-5, verified 3 separate times with dial indicator)
Checked rotary valve lash at 0.013-0.014 inches (spec is 0.010 - 0.014in, verified 2 times at 45 degrees with oring of cover removed)
Replaced battery as it failed load tests
Compression tested at 133ish lbs per piston. My rebuild a few years ago yielded 135psi per piston
Tested spark
Reattached exhaust pipe (separate issue, had come loose and was spraying water into hull)
Tested carb popoff. Mag side carb 40-42psi. Pto side carb 35-36 psi . Both carbs held 10psi pressure for several minutes (individually, and connected together).
Found y fitting of fuel line leaking air. Replaced. Performed pressure test of carbs again. Held 10 psi pressure for several minutes. No leaks
Brought idle of carbs up to 3000-3100 rpms on trailer. Around 1400-1500rpms on water.
New spark plugs. Verified gaps

@burtshaver2021 if i'm able to start the ski with only 25% ish throttle and no choke, wouldn't that imply I'm running slightly rich at startup/starting? The weird thing is, until July of '25 I was running the carbs a bit more lean than the manual states. I had them running at 1 turn out from closed. Now they are at 1.25 turns out from closed, like the manual says. The manual says to turn the low speed screw in/out 0.25 more/less than spec to help with tuning. I already was at that position before making this thread. Should i turn the low speed screw in 0.50 turns on both carbs to help lean it out?

The fuel block may be the next thing I check. I recall having difficulty installing that rubber grommet for one of the mylar discs. I don't think I replaced the other because of how hard it was to install the first.

Attached are the new plugs after running the ski no more than an hour. Most of that time was idling through no wake zones. I may have run the ski full blast for 10 minutes overall. Also the plugs smelled like the full synthetic oil I'm running. I've verified my oil pump timing is perfect, right on the mark.