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1988 25hp run problem

J

jacoby3mnk

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I have an 88 25 hp Mercury that has me baffled. I just changed plugs, plug wires and coils. Engine now starts but will not get boat up on plane due to lack of power. I have been adding Seafoam to my fuel the last year or so to help stabilize and clean the fuel system. Only about an ounce per 6 gallons of fuel mix. The motor acts like it is only running on one cyl. when I try to run faster than an idle. Should I be looking at the carburetor or something in the electrical system? My boat is a 16 foot john boat. Serial number on motor is OB222385. Thanks in advance for your time.
 
Only about an ounce per 6 gallons of fuel mix.
Click to expand...
To be more effective use 1 oz/gal. mix.
The motor acts like it is only running on one cyl.
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They will do that. While it is running use an insulated pliers to remove 1 plug wire at a time to see if it dies. When it does that is the problem cylinder. Using a spark gap tester check for a loud snapping blue spark that jumps 7/16" gap.

This will help http://issuu.com/cdielectronics/doc...t.xml&backgroundColor=000000&showFlipBtn=true
 
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it wouldn't hurt too take the carbs off and rebuild/clean them it doesn't sound like an electrical problem to me. When was the last time you cleaned the carbs ?? What type of fuel do you run ??
 
Spark is bright blue and has a snap sound to it when plug is out. checked that before starting motor after replacing plugs ,wires and coils. was only getting spark in one cylinder before replacing those parts. Last time carb was rebuilt has been around 12 years or so. Use mid grade gas and only Quicksilver 2 cycle oil.
 
i would go with a carb rebuild next the ethanol in the gas gums them up when it sits and if you arnt getting enough fuel it will run rough what is the numbers on your carb should be a WMC-11/12 or a WMC-26/27 and also can you tell me what carb you have between the images 7-9-2013 11-31-26 AM.jpg7-9-2013 11-30-52 AM.jpg
 
John, looks like the picture on left. the only numbers I see on the carb. wmc. 1-2. the 1-2 are not by the wmc. nothing else with the letters. any tips where else to look? no plates or anything on any of the blots. everything I have found are molded on carb itself.
 
took the boat to the lake last night to test out after rebuilding carb. Runs great on hose in driveway but same issue as before on the lake. Runs good at idle or slow speed, but when I open throttle if has no power. Where should I check next?
 
I took the boat to the lake last Monday night. Motor ran like it should. Went to the lake last night and the problem was back. Runs great at slow speed but when I try to open up the throttle no power. Any suggestions?
 
Can you "recap" here what has been done -

You rebuilt the carb.

Did you do the fuel pump while you were at it (new diaphragm)?

You were only getting spark at one plug then you replaced the coils/plugs/wires and now you have good spark at both plugs - correct?

Have you checked spark (even if you were underway) when it starts acting up on you? If you have an intermittent trigger problem (which, while not "common", it does happen enough that it should be considered) it may have been "working" immediately after changing the coils etc, giving you the impression that one of the replaced parts was the cause of the spark loss (a weak spark when it's acting up could indicate a problem with the high speed stator bobbin).

Have I missed anything that you have done to try and remedy this?
 
I did not pull plugs and the only difference between the 2 trips to the lake was Monday I had just mixed a tand of fuel while on my way to the lake. Did not burn 1 gallon from the tank and used same fuel on Saturday
 
Have you checked the fuel pick-up tube / hose inside the tank ?------On some plastic tanks those are nothing but " junk " and motor may run fine when tank is full and then act up as level in tank drops.
 
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