any sonic owners had a problem like this
 

a buddy of mine just got a 1997 31 with 502 efis after ideling a period of time the 1 motor when trying to take off shuts off and restarts hard idles but will take no throttle. after 5 minutes or so it will be ok and runs fine on plane till you idle a period of time again and does the same thing. the kicker is that the other motor has done the same thing at the same time and both acted the same way, so that kinda elimanates a motor problem or fuel pump making me think it is in the fuel tanks or valves for switching tanks, although it does it from either tank. wondering if it is a problem that sonic has had.

How about water in the fuel? Bad fuel? Any idea how long the fuel was sitting in the boat?

Did he tow that boat behind the F150? Wondering how it handled?

hey b whats new, any bites on your 31 yet, that will make someone a great boat as maticulous as you were with it and the price is good as well. yea he towed it with the 150 did ok but a 250 or 350 deisel is the way to go. as for the problem he is having we are looking into water in the fuel should know more timorrow.

He mentioned he was going to use his F150, there is nothing like the diesel torque when hitting those hills and good brakes. I should have done the electric over hydraulic from day 1!

We just put the boat up for sale this week on OSO, just a few questions coming in at this time. If it doesn't sell by Christmas, we'll probably use it for another season. We've been doing the dealers and went to the Liberty landing boat show and heading to Annapolis this weekend to check the various boats we might be interested in.

Tell your buddy good luck with his boat!

sounds like fuel to me....or maybe an electrical issue.are the drive bottles full? if they are down the rev limitter will kick in...

This Problem Is A Idle Issue , When On Plane Running It Works Fine.

I'd make sure tanks are cleaned and fresh fuel, then new fuel filters, if problem continues on both motors, I'd start looking at injectors - dirt from tank.... how do the flame arrestors look?

already did fuel filters. aresters are fine, a tank issue is likely due to both motors doing same thing.

Ran it Sat. 60deg. out ran great 72mph. Changed fuel filters, sarb. fuel pump, idled around came up on plane no problems sat for awile then idled across the river and came up on plane and the port moter shut down after about 3 min it startd up and everything ran fine??
Anyone have anymore ideas???

Don't think it is in the motors. It may be the fuel tank back flow valves. but I'm not sure where they are located. Are the in the tank control valve?? They are not in the fuel lines coming out of the tanks. Can anyone help on the location of these?

Start with the basics. As soon as a motor shuts down check spark and fuel pressure. At least that will give some direction. Most fuel pressure guages will allow you to take a fuel sample with the pressure release hose, make sure there is gas not water there while it's not starting. It may be there is water in the tanks that only gets sucked up when the boat is off plane and low in the rear, then rolls forward when on plane.

Thanks I will try that. I talked to Bruce today at Sonic. He told me that he talked to someone at mucury and they said they think it is vapor locking. I don't know. we are running out of good wheather here in Pa. I hope to fix it before winter.

check for a cracked coil. I had similar problems on a HP500-was very intermittent. When coil got warm the crack would open and get a spark to ground. Engine wouldn't give me rpm then and eventually just shut down. When engine got some cooler air would start and run fine until next heat up.
Crack was not visiible to naked eye. Only detected by hearing a cracking sound (arcing) and then darkening engine compartment and could then see the intermittent arc.

Thanks for the info, I think we may have figured it out, But I can't find out now until spring. I took it to get winterized and found that the motor with the shutting off problem was not charging and one battery was dead. my tech thinks that both motors could not run off of just the one charging? well new alternater later now I'll have to wait for warm wheather to find out.