OK...I thought it was fuel...and then reading the backfire thread, i thought maybe a wiring issue...BUT, i'm stumped...
Background: 35hp GTR 46hrs...totally clean tank, filled up with 100% gasoline(no ethanol) and seafoam...pulled the cover for the trim/etc and checked wires...everything looked great...engine still fluctuates/surges and will backfire...the first part of the video is bad due to the wind, however, bear with it and listen...about 25 seconds in, you'll hear the engine fluctuate rpms...the entire time, i'm holding the throttle constant...then i'll gun it, let off...and backfire...listen to the entire video...hope you guys can help me out...thanks in advance.
Woody
http://s155.photobucket.com/albums/s295 ... I_2044.flv

May be missing intermittently. You can check the ground wires to the coils, if they are shorting they will ground out the coil. Chaffed wires will cause it, bad harness too. You can isolate it to the harness by disconnecting the black wires at the coils and run it.

Note: With those wires disconnected you will have to kill it by choking it (key will not turn it off).

1st thing I would do is a leak down test. B&S is known for havin' valve issues on new engines. Seen one dis week wit under 100 hrs and the intake valves weren't seatin'.

Rod, i got your PM and number...i'll call you later when i can...heading over to Fayette-nam to see the Hogs play the south Carolina Steve spurriers...How do i go about doing a leak down test? Hopefully tomorrow i can get to the boat and pull the front cover and check the wires...the wires behind the trim looked good, no scrapes or bare wires...when i take the front cover off, can you guys be a little more specific of where i need to be checking. Thanks
Kurt Wood

Best way to do a leak down test is to take an old spark plug and break out all the ceramics so you have only the bottom metal threaded part. Then weld you air fitting to that. That way you can thread that in and hook up you air line directly to it then put the air pressure to it.

If you hear air coming out of the exhaust you have an exhaust valve leak... If you hear air coming out of the valve you have an intake valve leak... and so on.

HOGS WIN!!! WOGS WIN!!!!...now, ya'll get back to cypering what's up with my motor!!!
Woody

OK, tomorrow i'll go out to the rig and pull the front cover where the ignition is...other than wires that are exposed/etc. what am i looking for? Leak down test is getting way out of my comfort zone as far as "nut turning"...and my best engineer Mitschke is off doing that "school" thang.
Any advice will be greatly appreciated.
Woody

You can buy a leak down test kit. Heres a maintenance thread i put together it has the leakdown test explained Woody!
viewtopic.php?f=3&t=5837

Your looking for any wires that run into tilt trim panel that may have gotten worn down by your tilt / trim motor or pinched. On mine when my issues arose there was one wire barely shaved down on the sheath; it was down to the wire no bigger than a match head of wire showing. Some electrical tape and I tucked everything back up into the tilt / trim panel and put it back on. I'd start easy first before you start digging in deep.

Well, i checked the wires under the cover for the trim...i have tied in to the trim in order to put a trim out on the tiller...checked all of those wires and applied some more electical glue...the other wires all looked good. I haven't pulled the cover off by the ignition yet. I guess that will be my next project...after that, maybe i'll get the leakdown kit.
Woody

My engine did the same thing yours is doing at around 70 hours or so. My harness to my coils was rubbing and shorting out to my intake. You also should check the diodes in the harness. They have been known to go out. I would have suggested leak down sooner but from what Ive seen on here is most people freak when you try to explain how to do it. But if you have the tools it is a guick and easy test.

OK, so i need to be checking the ignition wiring and the spark plug harness wires...probably going to be friday before i can get to it. Also, i'm going to get a new exhaust, just trying to see what i can afford.
Woody