HELP MEEEEEEEEE pLeAsE

[jasonoberry352]

i have a 89 mercury 70 hp it starts and runs good but i'm loseing rpm's. last week after fixing the rpm gauge i was only getting 3200@ 22 mph,the boat usually does 30 mph acording to gps.in to the shop it goes ,he said only fireing on 2 cycinders rebuild kit four all three carbs.great i'm ready to see what she has only to reach 18 mph @2800 rpm wot?? five minits goes by i'm down to 15mph @ 2700 rpm. i can't even get on plain at this point all the way to 2500 rpm @12 mph. WTF!!!!! should'nt i be around 5200-5500 rpm?? any thoughts would help me get back on the water.also when rpm gauge was fixed also replaced trrottle cable f-n-r, new 2 me flywheel,new rectifier,timing double check,good gas,new fuel/water separator, new plugs,what else could it be??????????????????????????????????????????????????????????

 

[CharlieB]

Re: HELP MEEEEEEEEE pLeAsE

You still have to determine if you have a fuel supply problem or a weak ignition that is limiting power and RPM while under load.

UN-loaded it will Rev no problem, loaded, you need a HOT ignition and a fuel system capable of flowing plenty of fuel.

You didn't mention the fuel pump. Disconnect the fuel line before the carbs, point it into a suitable container. PULL THE LANYARD so the motor will NOT start. Crank the motor and observe the fuel stream, it should be a strong pulsed stream, no weakness, if it is slow and weak, remove the fuel pump and install a rebuild kit. Also check to be sure all hoses and fittings are in good shape, well clamped so as NOT to allow any air to be sucked into the line.

Remove the spark plugs and attach an adjustable gap spark tester set to 7/16 inch, re-attached the lanyard, crank the motor and observe for a hot blue snap on each cyl. This tests the low speed windings of the stator, the triggers, and the ignition module.

NOT able to reach WOT RPM after all the above is verified then you will need a DVA Meter or a DVA Adaptor for a Standard Volt/Ohm Meter to test the High Speed windings of the stator, as a low voltage here will also limit WOT RPM.

Test and re-test as there is NO RETURN on $$$$$$ electrical parts.

 

[jasonoberry352]

Re: HELP MEEEEEEEEE pLeAsE

first off thanks for replying. i forgot to say that i burned a quarter tank of fuel doing 14 mph , only ran for 40 minutes. usually burns less than half a tank all day. i think its getting the fuel, maybe just not burning it like u said.my mechanic said #2 cylinder was flooding out soaking the plug to the point it wouldn't burn, that's why he did the rebuild kits on all three carbs. so u think its a firing problem and nothing more serious????

 

[CharlieB]

Re: HELP MEEEEEEEEE pLeAsE

You still haven't mentioned if a compression test has been done.

Troubleshooting any problem starts with;

Compression test to verify the mechanical integrity of the motor

Spark test to verify the capacity of the ignition system,

THEN proceed to the fuel system.

Both compression and spark tests are simple, easy to do, and do not take more than an hour, at most, including the time it takes any shop to move the boat in and out of the shop.

If compression checks out and the ignition has a good hot spark, you still need to verify the fuel pump delivery as running out of fuel will limit power while in load, cause the motor to run lean, and melt pistons.

If fuel supply is good and RPM is limited then DVA testing of the stator high speed coils is needed as a low voltage here will also limit RPM while under load.

 

[mxzeatr]

Re: HELP MEEEEEEEEE pLeAsE

You said the linkage was replaced as well.

Is there a possibility that its out of adjustment and not opening the carbs fully???

 

[jasonoberry352]

Re: HELP MEEEEEEEEE pLeAsE

NO ,IT HAS BEEN CHECKED AND ALL IS GOOD. BUT THANKS 4 RESPONDING

 

[jasonoberry352]

Re: HELP MEEEEEEEEE pLeAsE

You still haven't mentioned if a compression test has been done.

Troubleshooting any problem starts with;

Compression test to verify the mechanical integrity of the motor

Spark test to verify the capacity of the ignition system,

THEN proceed to the fuel system.

Both compression and spark tests are simple, easy to do, and do not take more than an hour, at most, including the time it takes any shop to move the boat in and out of the shop.

If compression checks out and the ignition has a good hot spark, you still need to verify the fuel pump delivery as running out of fuel will limit power while in load, cause the motor to run lean, and melt pistons.

If fuel supply is good and RPM is limited then DVA testing of the stator high speed coils is needed as a low voltage here will also limit RPM while under load.

turned out to be a fuel line before fuel/water separator sucking air, guess the ethanol eats the gray lines from the inside out,replaced all lines with heavy duty black hose ,now the carbs could be adjusted correctly after a fresh rebuild on all three and no more problem runs strong. check simple things first is the lesson here!! thanks 2 all