575SCi backfire through exhaust
 

I have a 2002 29 Fever with a 575/XR. I have an issue with the motor starting, particularly when cold, but sometimes will do it when warm as well but not all the time. Motor will fire for a split second and then crank no start until I raise throttle position to 1/2 throttle. Motor will then immediately start and usually backfire out of the exhaust. Once running boat runs great. I understand this to be a rich condition, evidenced by going to 1/2 throttle cutting the fuel off. I believe it could be a problem with an injector however would like some insight if anyone has had a similar problem. Running fuel pressure seems fine per the gauge, new ignition components etc.

The 575's do have a problem with the injectors leaking. I believe they are NLA. Eddie Young has a kit to replace them with current injectors. We used my engine for the prototype and I can tell you that it never ran better after we ditched the injectors in the throttle bodies. As a side note, they also had terrible head gaskets. I pulled the heads on mine at about 100hrs and they looked like they were minutes from failing. I would do a compression test and if it has any low cylinders, do a leakdown test on the affected cylinders. Could very well need a valve job and some head gaskets.

I did a leakdown over the winter and everything looked good then. I did a compression test last weekend and all were within 5psi of each other. The weird part is I put a mech fuel pump in it as there was some standing fuel in the clear line, then went to lower elevation (2,000') that weekend and it never did it once the whole time. We ran over 150 miles over 3 days and not one time did it act up. Came back home the next weekend (4,000') and it did it first start. It does seem to be related to elevation but may be a coincidence I dunno. I plan on getting the injection setup from Eddie but was hoping to wait until winter. Might have to do it sooner I guess.

The 575 kinda has a bad reputation, but I really like it with a few modifications. Easily makes 700hp with a few upgrades. You could possibly have a problem with your MAP sensor or IAC . I lost a couple of IAC's on mine and they caused all sorts of problems. I always carried a spare on the boat. Probably need to put a scanner on it and see what the sensors are doing. You might try cleaning the injectors too. If you can find a local shop that has a Motorvac machine for injector cleaning, I would try that. I have seen them bring some questionable injectors back to life.

I would swap what Snap said.
Also what the others said- they are Notorious for head gaskets- nothing to do w back fire- but that is why I had to rebuild motors is when i lost on and Killed the motor before I knew I had an issue. If you are over 200 hours Do It. If not Do It anyway.
When I rebuilt- Brad punched out to 509's, full roller and other goodies- just dynoed this spring 785Hp. Very strong motors w a few mods.
AND the injectors are a big issue with Idle that I had until I replaced all of them.

Updated gaskets were installed before I bought the boat, I plan on replacing this winter again. I dont have access to a scanner at the moment, will try an IAC and see if that helps, sounds like those can cause a number of different issues and may not be bad to have a spare on board anyway if it isn't the problem now it could be in the future.....
Who's Brad? What are you using for tuning? Stock injection system with a modified tune? What did a rebuild like that cost roughly? When it comes time to freshin this thing up I am not sure what the best route to go is. Seems everyone knowledgeable on these motors is 1500+ miles away.

Brad Smith ( Smith Power ) Joplin, Mo we lost him and Jeff years ago.....RIP