Stalling and back firing????
 

Yesterday my 2008 X15 was doing this, it would run fine that after about reaching running temp 160 it would start to do this. It goes worse through out the day and even died when put in reverse pulling up to the pier. I am assume it was going into limp mode. It is the MCX engine.

I know this is hard to say but thought i would see where I should start to look. To me it seems like I got water in the gas. Is there a fuel/water seperator or fuel filter. Or I live on a VERY weedy lake so could I have sucked weeds up in the heat exchanger? the odd thing is I temp gauge never got over 160 ( I wonder if that is bad)

I doubt it. Most fuel injected Mastercrafts (Other inboards too?) don't. I don't think you'll have a filter either and there is just a metal screen on the pickup on the fuel pump. To clean it you have to pull the pump which I hear is a bit of a job and not a typical maintenance item.

Turn the ignition to the on position to run the fuel pump then take a shot of fuel into a glass jar from the shrader valve on the fuel rail. Let it sit for a few mins and see if you can see water at the bottom. It will look like a bubble forming under the fuel.

Just for good measure take off your spark arrestor (Air intake) and clean it with some degreaser and water. It could be caked with crap but I doubt it would be that bad on an '08.

If all that checks out get a fuel gauge ($30 or so at AutoZone) on that shrader valve and watch it as you're experiencing the behavior to see if it's dropping off. You'd have to do some research to see what the appropriate pressure should read for the '08 MCX.

Oh, pull a couple of the sparkplugs and look for damage or excessive carbon buildup and make sure the boots are securely snapped on to each plug. Check the gap and make sure it's within spec. If they're out of spec you might as well change them since they're not terribly expensive and you'd have to remove them all to re-gap anyway.

Can you rev it up in neutral or does it pop and stall then too?

I would think if your temp gauge rates up progressively to 160 as the engine warms up it's probably fine and cooling likely isn't your issue.

back firing through the intake or the exhaust ?

I can put it in neutral and rev it fine, no issues. It seemed to be backing from the intake, I dont think you would be able to hear it from the exhaust in the water???

some more info. I did have the boat loaded with people and it was very choppy. It first starting acting up when hitting some big rollers. can it just be vapor lock? Almost 200 hours and I have never changed the plugs

Most likely water in the fuel. Put some Seafoam in the tank, and change the fuel filter.

^^^ I don't think there is a fuel filter???

I did pull the cap off and it seemed good and dry to me. So not sure what else to check. Any ideas?

Take a look at your distributor (cap and rotor). Mine was toast and it did the same thing.

Toneus

well it is the fuel pump which I understand is common issue. so now I am looking for a replacment pump. does anyone know a autozone or napa part number for a replacement???

Yes, it's an AutoZone/Napa part. Not sure which part # you would need though. check the mastercraft forum. http://www.mastercraft.com/teamtalk.

That said it's quite a task to change and isn't terribly cheap so I would hookup a fuel pressure gauge first and make sure that's the problem. If the specified pressure is maintained when your fuel pump is fine so look elsewhere.

If your boat is an 08' and you have a fuel pump issue why aren't you trying to get it replaced under warranty?

Maybe not a spin-on water separator, but there has to be a filter of some sort. Mine is a little silver can between two threaded fittings in the metal part of the fuel line, attached to the side of the motor, right next to the fuel pump. It's the same exact filter that my (99 Chevy) truck uses, too.

You can take your fuel pump in to a good auto parts house, and if they carry it, they will probably be able to identify it. I'm not talking about a high school kid working the counter at Autozone, but an old guy at an old, dirty auto parts shop. They still smoke cigarettes inside at the best ones.

Do you know how much gas you had in the tank? Our XStar, would do the same thing if it got below half a tank. It was a bad fuel pump, and it is a job to replace it. It was under warranty and it turned out to be an 800.00 job (labor and parts). And I am almost positive you have to drain the tank to change it.

Read through this thread:
http://www.mastercraft.com/teamtalk/...ad.php?t=37122

Good MCX specific info as well as part numbers for the pump.

I did test it with a guage and that is how I realized what it was. I found the pump I needed on the NC forums along with a lot of other info about pumps. It was a very easy job, in fact I heard of peopl doing them out on the water. Drove the boat today and no issues. The pump and filter is in the tank, filter was fine.

MC only sells the whole modular, reg, bucket ,pump assembly and it is $480 where as I just pulled out and replaced the pump and it only cost me $90

No longer under warranty