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1989 Black Max No Acceleration

M

markk

New member
I just had the chance to get my boat in the water after replacing the entire motor, I replaced it with a slightly used motor. The motor runs good at the dock and rev's up when using just the throttle lever, however when I shift into gear and start out is idles up to a point then nothing for acceleration. It seems as though the spark advance is not working or something like to that. The compression is good 115-120 for a motor this old, I checked the linkage and all seems to work properly. Any ideas???
 
Perhaps there is a problem with carburetor jets.-------This needs to be checked before anymore trial runs as a plugged carburetor will also starve a cylinder of oil.------Check to see if there is spark on all 6 cylinders as well.
 
I haven't pulled the plugs out yet, but I would figure it was running rich. When I was in gear and throttled up, the tach rose to about 1200-1500 rpm and it was just bogging, if I stayed with the throttle in that position it was slowly choking the motor out. If I took it out of gear the engine would idle fine and rev up just not when it was in gear or under load....But I will check the plugs today...
 
pulled the plugs out today and they are all wet so I know I was not getting a lean condition, I am still leaning towards the ignition somewhere. I will check that the coils are firing but, at idle and with the manual throttle lever is runs smooth.
 
They will run surprisingly well on 5 cylinders and even on 4 cylinders.----Spark must jump a gap of 3/8" or better to be called " good spark "
 
It almost sounds like a WEAK total ignition system. As speed is increased, So is the need for a fully powered spark. As load is increased so is the need for a SMASHING BLUE HOT SPARK. Testing in air is helpfull 99 % of the time. But a system needs to fire in the full compression of the cylinder.

I use a different spark test sometimes. Can be dangerous. Needs a seperate driver. Pull the engine cover off. Wear a THICK rubber glove to resist getting shocked in a metal boat. I replace the rubber booted plug wire with a cable that has the BARE METAL plug end. At maximum speed I slowely pull the metal cap off a LITTLE bit. See if we still have a BLUE ZAPPING BUZZ at high speed. Good ignitions always have that BLUE ARCING.
 
cyclops2 said:
It almost sounds like a WEAK total ignition system. As speed is increased, So is the need for a fully powered spark. As load is increased so is the need for a SMASHING BLUE HOT SPARK. Testing in air is helpfull 99 % of the time. But a system needs to fire in the full compression of the cylinder.

I use a different spark test sometimes. Can be dangerous. Needs a seperate driver. Pull the engine cover off. Wear a THICK rubber glove to resist getting shocked in a metal boat. I replace the rubber booted plug wire with a cable that has the BARE METAL plug end. At maximum speed I slowely pull the metal cap off a LITTLE bit. See if we still have a BLUE ZAPPING BUZZ at high speed. Good ignitions always have that BLUE ARCING.
Click to expand...

yeah that sounds a little dicey at 70+ mph........Let me see what I can find out in the driveway and some water in a bin........
 
Ok , so the coils are firing had a hand held indicator showing me that the spark is hitting the wire, I could understand if I had a few not firing.....
 
Bogging upon accelleration has to be a carb issue. Your plugs were wet. So were mine yesterday...a bit of oil coating but it runs great at WOT. It bogged last summer, RPM was down 1K, rebuilt the carbs and she runs perfectly w/o bogging.
 
Cleaned all the carbs and found the middle carb float bowl loaded up with crud. Three cans of carb cleaner and they look as good as new. Took it to the launch and throttled it up and came up to power. Tach is still not working but, at least I can go do some fishing... Thanks to all of you with your responses and tips........Mark
 
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