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70 hp 1980 Johnson hesitates upon throttle above idle

Post By: manoverboard      Posted: 4/10/2007 7:21:14 PM     Points: 79    
Okay...another boat post. I bought an old boat and need to make it right. Yesterday the boat would only accelerate after I put in neutral and lifted the lever on top (it says "start" and "fast idle") for aboiut a minute, put the lever down and then immediately put into gear and pushed the throttle past slow. If I didn't do this, when I put it into gear, it ran perfectly as long as I didn't give it any gas (it would die if I did).

Any and all info will be appreciated. I need to fish instead of mess with my new boat!
 Reply by: Matt      Posted: 4/10/2007 8:46:00 PM     Points: 89392
I'm no motor expert and have had my share of issues to deal with. Do you have a water separator? If so you may want to replace it. Also the spark plugs. You may also have carb issues an may want to try some carb cleaner. Engines act differently when they're under load, so if it's running OK in neutral but not in gear, you probably have something going on with the fuel and combustion. Also check the gas cap on your tank and make sure the vent is clear...replacing the cap could be a cheap fix.
 Reply by: Fishinbud      Posted: 4/11/2007 8:37:54 AM     Points: 0
I've gotta' agree with Matt. I have a Merc 40 HP (1997) and on occasion it will run really sluggish (for no apparent reason, at the given time, usually, every couple of years). When that happens, it's almost always either fouled plugs, which should be cleaned or changed out (every other year at least) or there may be carberator issues. One more possibility, is a defective water pump (which should be replaced about every 2-3 years). If that's the case, you'd see restricted outflow of water from your motor.
Start with the spark plugs (an easy quick fix) and move up from there. A rebuilt carberator will probably run you in the $350-500 range and a water pump is a couple hundred (hopefully that is not what is wrong with your engine). Finally, it's always a good idea to run some sort of fuel stabilizer all year long, like Stabil. That way, you never have to worry about your gas going bad and gumming up the engine (especially during winter storage periods). Also, it will help your engine run much smoother during the open water season as well. I hope that this helps, good luck!
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