jrm45
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Motor Problem
got a small issue for any of you motor heads who know more than me.... went out today just for a cruize, everything started fine.. cruized around the lake for about 45 minutes than decided to pack it in and head home...turned around to head back to towards the channel (i dock right on state street).... gave it some gas and when i got above 3k rpm, the motor would start to die down..... reve up and down and up and down... first time its ever did this... same if i gave it more gas.... The boat is a 1982 27' chris craft scorpion 264 with a mercruser 260 (350 CI) in it..... kept doing it every time i gave more gas... had to cruise back at about 15 knots... normally 25 - 29 is easy going for her.... im thinking its something to do with it not getting gas.... but i dont know... and it was fine till i decided to head in...
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BIGSLICK
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RE: Motor Problem
2009/08/04 20:57:58
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Well....Could be alot of things...Sounds like water in gas or Vapor lock.....Could be clogged filters...Do you have a water seperating filter? Could be carb....Could be points/weak spark..Could be when your coil gets warm, it's resistance is changing and throwing off your spark......I would start by checking filters...Then move past that and move to plugs/wires/points......Then to carb....Add some Carb Cleaner additive (Not the cheap stuff either) and some Seafoam with some new gas...Keep us posted on how she runs...
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pghmarty
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RE: Motor Problem
2009/08/04 21:12:11
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water separating fuel filter
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jrm45
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RE: Motor Problem
2009/08/04 21:17:45
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guys, thanks for the responses. im leaving out of town 2morrow for a few days but will start checking these things when i get back over the weekend... once again, thanks alot!!!
post edited by jrm45 - 2009/08/04 21:18:03
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kingnuke32
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RE: Motor Problem
2009/08/04 21:46:40
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Dump seafoam in the gas tank and get an H20 seperating filter, ethanol sucks!
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BloodyHand
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RE: Motor Problem
2009/08/04 23:53:27
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Had the same problem a couple years ago. Replaced the filters, still no luck. Had to tear the fuel system apart to find the problem. We found a little piece of plastic snot stuck in the check valve. Weird! My Buddies were happy as I filled like 5 cars up with free gas that day.
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spoonchucker
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RE: Motor Problem
2009/08/05 00:01:44
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Check all fuel lines (connections ) as well. Could be a slightly kinked hose. or "sucking air" through the line.
Get Informed, Get Involved, And Make A Difference. Step Up, or Step Aside The next time you say "Somebody should do something", remember that YOU are somebody. GL
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grimm reaper
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RE: Motor Problem
2009/08/05 00:13:15
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i had the same promblem last year with my old boat but mine was the fuel pump
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17targa
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RE: Motor Problem
2009/08/05 00:35:23
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I had a similar problem a couple years ago after changing spark plugs. I pulled 1 plug out and took it to a dealer to get replacements for it. The tech looked at it and said "the exact same spark plug would be $20 each, but I have another equal spark plug for $7 each and there will be no difference." So I opted for the cheaper ones that were supposed to perform the same. I put them in and my boat ran exactly like you described for the next couple outings. Since the only thing I knew I changed was the sparkplugs I started to do some research on the internet. It turns out the $20 plugs had a built in resistor which blocks out frequencies from electronics like your gps or sonar. Without the resistor the frequencies would disrupt your ignition and cause the change in rpms and motor performance. So needless to say I went to another dealer to buy the $20 plugs and the motor has been running fine since. Just throwing this out there if you happened to change plugs recently or added a sonar or gps.
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BIGSLICK
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RE: Motor Problem
2009/08/05 01:20:31
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ORIGINAL: 17targa
I had a similar problem a couple years ago after changing spark plugs. I pulled 1 plug out and took it to a dealer to get replacements for it. The tech looked at it and said "the exact same spark plug would be $20 each, but I have another equal spark plug for $7 each and there will be no difference." So I opted for the cheaper ones that were supposed to perform the same. I put them in and my boat ran exactly like you described for the next couple outings. Since the only thing I knew I changed was the sparkplugs I started to do some research on the internet. It turns out the $20 plugs had a built in resistor which blocks out frequencies from electronics like your gps or sonar. Without the resistor the frequencies would disrupt your ignition and cause the change in rpms and motor performance. So needless to say I went to another dealer to buy the $20 plugs and the motor has been running fine since. Just throwing this out there if you happened to change plugs recently or added a sonar or gps.
Never heard of that....Was it an I/O or a outboard?
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spoonchucker
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RE: Motor Problem
2009/08/05 01:30:01
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Non resistor plugs, should interfere with your electronics. Not the other way around.
Get Informed, Get Involved, And Make A Difference. Step Up, or Step Aside The next time you say "Somebody should do something", remember that YOU are somebody. GL
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BIGSLICK
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RE: Motor Problem
2009/08/05 01:49:29
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I was gonna say...I have heard of Ignitions interfearing with electronics, but never electronics interfearing with ignitions....Sounds like you just didn't get a hot enough plug or didn't gap them correctly.........$20 for a spark Plug???......Go to NAPA and get some NGK's...$2 a peice...Or take the existing one out and take it their for them to cross it..They can most likely cross it even if it's an OB with odd plugs......You overpaid by about 1000% per plug.....Typically....A plug that contains an R at the end of the plug # is Resistive, and most applications are....
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17targa
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RE: Motor Problem
2009/08/05 01:54:41
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It was an outboad. From what I found on the internet the interference could go both ways, but then I am no electrical genius. I will see if I can find the information again about the plugs and post it on here. All I know it definately fixed the problem.
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pghmarty
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RE: Motor Problem
2009/08/05 01:59:25
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but I have another equal spark plug for $7 each and there will be no difference. Marine sparkplugs are plated to prevent rust at the motor and where the wrench makes contact. He probably looked at a conversion chart and picked the wrong plug. A a lower heat range or wrong length plug (base of threads to the tip of electrode) was probably the problem. Resister plugs usually have an "R" somewhere on their # He gave you a $3 automotive plug for $7 instead of a $4 marine plug for $20 
post edited by pghmarty - 2009/08/05 04:07:02
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BIGSLICK
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RE: Motor Problem
2009/08/05 01:59:44
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ORIGINAL: 17targa
It was an outboad. From what I found on the internet the interference could go both ways, but then I am no electrical genius. I will see if I can find the information again about the plugs and post it on here. All I know it definately fixed the problem.
Cool....That would be a new one to me though...I have heard of Ignitions messing with RFI in GPS and Radar units though....
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17targa
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RE: Motor Problem
2009/08/05 02:05:54
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BIGSLICK
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RE: Motor Problem
2009/08/05 02:09:58
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ORIGINAL: 17targa
This is the information taken straight off the NGK website.
http://www.ngksparkplugs.com/tech_support/spark_plugs/faqs/faqresistor.asp?mode=nml
In fact, using a non-resistor plug in certain applications can actually cause the engine to suffer undesirable side effects such as an erratic idle, high-rpm misfire, engine run-on, power drop off at certain rpm levels and abnormal combustion.
No ****.....Never heard of that........Then again, never put non-resistive plugs in a boat motor either....???.....Thanks for the info
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Dream Catcher
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RE: Motor Problem
2009/08/05 06:29:02
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I put non resistor style in my 230 CID 4cyl I/O motor ran just fine but my ship to shore would not work ; not to mention the rust that gathered on them ... Replaced and this year I can use the ship to shore . Problem sounds like a fuel filter ........ or maybe bad gas ........
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BloodyHand
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RE: Motor Problem
2009/08/05 07:32:53
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Thats where I'd start JRM45. The consensus here is it sounds like a fuel delivery problem.
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runtgetter
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RE: Motor Problem
2009/08/05 11:05:43
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i had a 181 ci mercruiser with the same problem.It turned out to be several problems.the points were slightly tarnished, a rubber fuel line was cracked in a place that was hard to see(wich leaked air at 3k rpm).the problem ws getting better, but wasnt quite right.turns out there was some debris caught in the carb.a very nice fellow was kind enough to help.he did something with a screwdriver while i gunned it.havent had any problems since.he told me what he did, but dont remember.maybe someone else is mechanicly inclined and knows what this feller did.good luck
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pghmarty
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RE: Motor Problem
2009/08/05 12:31:01
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He might of tapped on carb to loosen stuck floats or adjusted idle mix screws
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jon_e_si
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RE: Motor Problem
2009/08/06 06:20:18
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Bought an older pontoon with 50HP, had trouble with it starting, running etc. - noticed squeeze bulb on fuel line was soft and apparently had a leak! On an '82 model, you could have osmething similar!
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Frenchy
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RE: Motor Problem
2009/08/08 17:23:09
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Go to http://forums.iboats.com/ and post the same question on the appropriate forums. Or read thru the countless threads after searching for your problem. Very helpful site for the DYI type of person.
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