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early 80's 80hp running rough

N

novice_marine

New member
engine acts like it runs out or gas, will rev out and sound very good for a minute or so them lug down and die. it will not idle right and i can not get the idle adjusted up. but the engine is clearly not running out of fuel, you can look down the carbs and watch the main jets flow none stop untill the engine dies. and if i try to squeeze the primer bulb to get a little more fuel to it, the engine will immediatly shut down. the plugs seem to have good spark, but when you pull them, they are soaked with oil. i am mixing the gas 50:1. the engine sat for about 3-4 years before i bought it. it has NGK plugs that are flat on the electrode end, i did not write down the number sorry. it has to be something simple i'm over looking, when the engine is running, it runs great, but about the time the boat wants to come onto plane, it looses power and shuts down and won't start for a few minutes. any sugestions will be great.
 
Try this - with the motor off and the hood off and the motor tilted slightly (to about the 3rd or 4th hole on the tilt (thrust) pin) - then pump up the primer bulb - if you get gas flowing out of any of the carb throats, rebuild the carbs - the float valves are stuck.

All your symptoms can be explained by flooding.

And that would be an "expected" consequence of a motor sitting for a number of years...
 
please expand on fuel pump "broken". it is pumping fuel, but too much, i do not know.

galamb,
yes, it is just as you described, i noticed this early on, if you pump the primer too much, fuel will flow out of the carbs, but i can not see where exactly it is coming from as far as a certain jet or port. it just seems to flow out of the base of the carbs, or the intake manifold. i now have carb kits ordered. are they too much differant from any other cross flow bowl type carbs that would be on a truck or tractor? or is there some trick or secret to re-build and then adjust? thanks.
 
If the fuel pump diaphram is torn or perforated, it (leaks) directly into the crankcase causing a flood "behind" the carbs.

And the carbs themself are mechanically no different than what you would find on a tractor etc - no real trick to rebuilding.

If you don't have the specs simply figure out how any adjustable needles are set before you tear down the old ones - "seat" the needles and just count how many turns it took then install the new ones (or reinstall the old ones) to the same count.

Although I have done it a few times I can usually rebuild a multi-carb setup in about an hour - including removal and re-installation (no counting "soaking time" if they are really clogged).

You can use carb cleaner on any metal parts but keep it away from plastic or rubber. Unless things are really clogged I tend just to soak with isopropal alcohol (gas line anti-freeze - 59 cents for the little bottle you add to your car) and then blow out with compressed air - it's not as harsh as regular carb cleaner....
 
hit the nail on the head, you can see through the pump diaphram, i don't know how it was even getting fuel to the carbs. thanks alot, maybe one day i'll get these 2 strokes figured out, they're kind of a differant animal.
 
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