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View Full Version : No Acceleration, Backfire! Please Help!!!


jwweathers
06-13-2013, 06:05 PM
I am new to this forum. Through reading many of the threads, it is obvious that many of the contributors here are very knowledgeable. I am hoping someone can give me some pointers as I am having problems with my 2003 MC 205V.

Before I winterized my boat last year it was hesitating during acceleration which led to a new fuel pump. Following the fuel pump replacement, it ran flawlessly. I put it in the water for the first time of the season a couple of days ago. It cranked with no problem. However, when I tried to accelerate, the engine was not cooperating, and I could not get the boat on plane. The engine even backfired once when attempting a hard acceleration.

After noticing the problem, I replaced the cap, rotor, and plugs. No change. Any ideas???

Thanks,

Jeff

PA Prostar
06-13-2013, 06:19 PM
I am new to this forum. Through reading many of the threads, it is obvious that many of the contributors here are very knowledgeable. I am hoping someone can give me some pointers as I am having problems with my 2003 MC 205V.

Before I winterized my boat last year it was hesitating during acceleration which led to a new fuel pump. Following the fuel pump replacement, it ran flawlessly. I put it in the water for the first time of the season a couple of days ago. It cranked with no problem. However, when I tried to accelerate, the engine was not cooperating, and I could not get the boat on plane. The engine even backfired once when attempting a hard acceleration.

After noticing the problem, I replaced the cap, rotor, and plugs. No change. Any ideas???

Thanks,

Jeff

I'm not an expert by any stretch of the imagination, but are you getting spark (wire and plug) in all the cylinders? That would be the easiest to check. Timing also comes to mind. Lastly, would be the valves not seating properly. All that being said, it's probably something entirely different.................... The backfiring has my interest - although you said only once.

thatsmrmastercraft
06-13-2013, 06:29 PM
Backfiring and hesitation are often experienced when two spark plug wires are out of sequence. I know from experience. I would verify that this didn't happen.

jwweathers
06-13-2013, 07:59 PM
I thought about the plug wires being swapped. However,the problem began before I changed the plugs, cap, and rotor. Since I didn't touch the boat over the winter, I think that issue has been ruled out. Thanks for the tip, though. I appreciate the feedback! Keep it coming so I can get some time on the water.

Jeff

jwweathers
06-13-2013, 08:01 PM
Also, the oil pressure seems a little high. Reading 40 psi at idle. It may be important to note that the engine idles smooth. However, it took a couple of tries to get it started after letting it warm up.

Jeff

madcityskier
06-13-2013, 09:39 PM
Checking the plug wires is #1, also the easiest and quickest. #2 would be timing, IMHO.

TayMC197
06-13-2013, 10:21 PM
Check the battery charge. Not enough juice = poor ignition. Ran great first time cause battery was charged, now battery is low, alternator might be bad or have bad connection.

TayMC197
06-13-2013, 10:23 PM
Sounds battery/grounding related to me.

j.mccreight@hotmail.com
06-13-2013, 11:25 PM
Which motor? I would check fuel pressure.

jwweathers
06-14-2013, 12:06 AM
It's the mcx 5.7 liter vortec V8. New battery. I will check the alternator/ground, but I am starting to think it is a fuel related issue. Very frustrating!!!

Jeff

Jerseydave
06-14-2013, 12:14 AM
You said it ran flawlessly before winter layup. Who winterized it? Did they remove the plugs to fog the engine? (this is the proper way to fog an MCX) Perhaps 2 plug wires are connected wrong by that person. Did they remove the knock sensor to drain water from the block, and if so did it get plugged back in?
Your firing order is 1-8-4-3-6-5-7-2. Best check that first.

If everything above checks out, you could pour some seafoam in the gas tank and see if that helps.....but it sounds more like ignition related to me.

jwweathers
06-14-2013, 12:26 AM
Checked the firing order, and everything looks correct. I will try the sea foam. Fingers crossed! Thanks.

Jeff

South TX MC
09-15-2014, 09:07 PM
JWWEATHERS...how did you right the problem? I'm having very similar problem(s). This past weekend boat would launch out of the hole, plane and take off but in about 30 seconds thereafter multiple backfires, poor acceleration, etc. at speed. I pulled back throttle to 20% and worked fine, trolling speed is fine, oil pressure & temperature was normal.