1988 80 HP MERC CAN NOT ACCELERATE CARBS APPEAR FLOODED

[hafriends]

My dad owns a 1988(or 89?), 80 hp, 2 carbs, and 4 cylinder Merc. The motor was started up from winter storage about 3 weeks ago and barely idled. When the throttle was advanced the motor barely revved. Boat speed was no more than 5-10 mph at full throttle. Knowing my Dad(he thinks plugs will last forever) I bought a replacement set of plugs and popped them in. The motor ran very well(especially at high speed). He attempted to start the motor 1 week later and the motor would not start. He had a friend who knows Mercs. come by, and the guy said there was some gizmo in the electrical system that periodically gets overloaded and prevents the coils from firing. He fixed that and then the motor started right up. But, there was no top end power(yet again). My Dad had another Merc mechanic friend check it out at the dock(he did not take it out for a spin) and that person adjusted the low and high speed idle.<br /><br />Yes, I was shocked when I heard he adjusted the high speed idle dockside without the motor under load. Anyway, that solved nothing. I decided to have a go at it myself(I had a little business fixing OMC outboards when I was younger, as well as being car mechanic in those days as well). Now, I don’t profess to be a Merc mechanic, but I wanted to have a look. I popped off the complete cowl and got underway. At full throttle(about 5 –10 mph) I noticed raw gas pouring into the venturies from what appears to be the feed pipe that might feed the engine extra gas under peak acceleration. I immediately suspected that the high idle was completely out of whack, but since I’m no Merc mech, I could not identify the high speed idle screws. I noticed a screw on the lower right of the carb, and I suspected that was the low speed. There was another screw on the upper left, but I could not turn that and I didn’t want to be too forceful with it. Anyway, I decided to seek help at this site on what the problem could be as well as where the idle screws are. Who knows what that could be? Also, the motor has stopped running again. It simply won’t start.

 

[The Marine Doctor]

Re: 1988 80 HP MERC CAN NOT ACCELERATE CARBS APPEAR FLOODED

Check for compression and spark.<br /><br />If fuel is spewing out of the carbs..you likely found your answer.<br /><br />Remove and rebuild them as for the highspeed jet...only way to adjust them is with a DRILLBIT. <----sarcasm as you cannot adjust them. <br /><br />TMD

 

[greasemonkeyozi]

Re: 1988 80 HP MERC CAN NOT ACCELERATE CARBS APPEAR FLOODED

Hello hafriends and welcome to this site. I'm not an administrator to this site, nor a full time mechanic on boat motors, but your problem does seem like a typical motor problem, and maybe I can help. <br /> You stated that you have recently removed your motor from winter storage and just now having motor problems.<br /> Sounds to me you are having a fuel problem.<br /> 2 cycle mixed fuel breaks down after 3 months. It looses it's octain. If you havnt yet, change out that old fuel.<br /> Second, while motors are stored up for a long time, especially during winter storage, old fuel that is left in the system turns gummy, like tar. <br /> It dont take a rocket scientist to work on carborators. Remove your carborators from the motor, careful not to rip the gasket, and inspect them for clogged jets or gummy stuff inside them. With your mouth, blow where the fuel line attaches to the carbs. A perfect flow of air should be present. If not, your jets are clogged. You can clean them out with a wire and carb cleaner. Inspect your floats and make sure they work. <br />Do this for both carborators.<br /> Yes, those screws on your carbs next to the butterfly are adjusting screws. Try this. Turn your screws clockwise as if you are tightning it all the way clockwise. DONT TORQUE IT, dont even snug it, just when you feel it screwed in all the way. "If you over tighten them, you will taper out your needle." OK, now, rotate the screw counterclockwise exactly 1 1/2 to 2 full rotations. Try 2 rotations. Now your carbs are in the right tuning area.<br /> One good idea is to go ahead and rebuild your carbs. You dont really need a complete rebuild kit, just buy new floats, needles and needle seats, and gaskets for both carbs.<br /> Another thing that I have learned that contributes to your problem is the fuel line and the fuel pump. While the carbs are off the motor, or before you do take the carbs off, disconnect the fuel line going to the carbs, have someone attemt to start the motor, and check to see if the fuel pump is pumping good. Fuel should be flowing out with a good amount of pressure.<br /> Rebuilding your fuel pump is a really easy and inexpensive job. You can buy a fuel pump diaphram kit for your motor for about $4.00. All it is is a thin paper like plate that somehow uses vacume from your motor to pump fuel. Again, you do need to do this because old fuel could have gummed up something in your pump. Also, look for a hole in your diaphram befor you replace it, if there is, thats your problem.<br /> OK, heres another note. I had this problem and it might help you out also. That connector on the fuel line that connects to the motor itself has a rubber O ring in it. There is a possability that air is getting inside that fitting due to the O ring being dryrotted. You can buy that part at wallmart along with other basic fuel line parts such as the bulb, fuel tank fittings, and the line itself.<br /> While diagnosing your motor, check your electrical system. That thing you was talking abou that disributes power to your coils is called a switch box. To check out your electrical system, remove your plug wires and ground them to the motor. Have someone attempt to start it and check each plug wire for spark by holding it close to the plug. If a plug is not firing, let us know.<br /> One cheap and easy way to attempt to clean out your motor is something called SEA FOAM. You can get this at NAPA. This stuff works wonders, its like a tune up in a can. Take your spark plugs out and spray a good amount in your cylinders. Let set for an hour, or over night, and start your motor. Then spray some in each carborator and watch all kinds of nasty junk blow out your exaust. This stuff works wonders, its like getting your fuel injectors cleaned on your car. Once your motors fixed, use about 1/2 can per 3 tanks fuel. This is some good stuff, trust me. It might even fix your problem.<br /> I appologise for typing so much, I just enjoy doing what it takes to get my fellow fisherman back on the water. Good luck, and let us know how it goes.<br /> P.S. keep an eye on your topic, another mechanic may have more good advise.

 

[greasemonkeyozi]

Re: 1988 80 HP MERC CAN NOT ACCELERATE CARBS APPEAR FLOODED

Oh yeah by the way hafriends. I advise alot of boat owners to install an inline fuel filter on your fuel line from your tank. I see so many fuel problems on this site due to clogged jets. All it takes is a tiny tiny piece of trash the size of a grain of sand from your tank to clog a jet. You can prevent this by buying any cheap filter that will fit your line. Just cut the fuel line, and slide it in your hose and use hose clamps to seal the line. As a matter of fact, most boat moters dont use hose clamps on the hose ends and connections, why, I dont know. <br />I went ahead and used hose clamps on all my hose connections to prevent intake of air. Use tose kind that screw tight, not those cheap zip ties.