NO POWER out of mercury 8500 1975

[kickinchicken]

what prop do you have on it? what do you call good compression?

 

[tompowers85]

NO POWER out of mercury 8500 1975

I have a 1975 mercury 8500 outboard. The engine starts right up but it only goes about 5-10 mph at full throttle. I have rebuilt the carbs and replaced prop, all fuel lines, and spark plugs. I am not sure what to do. I have good compression in all cylinders too.

 

[NathanY]

Re: NO POWER out of mercury 8500 1975

Check for spark on all cylinders. Sounds as though you might be dropping a cylinder while under a load.

 

[Laddies]

Re: NO POWER out of mercury 8500 1975

Ck your carb. pick up and opening and timing

 

[Yepblaze]

Re: NO POWER out of mercury 8500 1975

Test for fuel starvation by hitting the choke momentarily while trying to accelerate.<br /><br />Also try squeezing the fuel primer bulb while trying to accelerate.<br /><br />If either of these momentarily seems to correct or help the situation then You have fuel starvation issue(s) that may need correction. (and perhaps along with other unknown issues)<br /><br /><br />If no improvement is found while trying those diagnostic procedures, continue on with ignition being suspect.<br /><br />Check for good spark at all spark plugs. And make sure firing order is correct to the motor.

 

[tompowers85]

Re: NO POWER out of mercury 8500 1975

The compression on the carbs was 100-105 psi on all four cylinders. I got the prop used and had it repacked at a merc dealer, it is in good condition i had it packed as a precuation. <br /><br />I have some fuel leaking from the carbs, even after i rebuilt them both. I thought it might have been the floats, which were saturated, the leak is not as bad as it was. I do have to prime the ball a lot, and have trouble keeping pressure in the lines. I did prime will running and it did not do much. I am going to change the distributor cap and spark plug wires the plugs are new.

 

[Clams Canino]

Re: NO POWER out of mercury 8500 1975

Don't waste your money on cap and wires, it's not a car and you'll go broke for nothing.<br /> <br />Stay with the fuel system - it sounds like it has issues still.<br /><br />-W

 

[tompowers85]

Re: NO POWER out of mercury 8500 1975

I am going to replace every fuel line and from the tank to the carbs. I am still having problems with keeping the pressure in the lines. When i prime the ball the fuel starts leaking from the carbs. At the bottom of the carbs is a tray that gathers the fuel that runs off, but it seems like i am still getting to much fuel running out. I rebuilt everything in the carbs, and it helped the problem some. Can anyone tell me how much fuel should leak? The primer bulb should stay hard the entire time the entire time the engine is running correct?

 

[Clams Canino]

Re: NO POWER out of mercury 8500 1975

*No* fuel should leak if the carbs are properly rebuilt. If the float check valves leak, it will cause the leaks. If the float is a "sink" - it'll cause the leaks. The tray catches fuel that leaks when you tilt the motor out of the water.<br /><br />When you pump the ball it should get hard, but running the motor will soften it up as the thing vacuums fuel.<br /><br />-W

 

[tompowers85]

Re: NO POWER out of mercury 8500 1975

I redid all of the lines and i found a leak in one of the lines. I do have a small leak from the injector in the front of the carb. It only leaks when the bulb is fully primed. Is that ok or does the injector need replacing? The leak is only a small drip.

 

[Chris1956]

Re: NO POWER out of mercury 8500 1975

Tom, These motors do not have "injectors". You may be seeing fuel drip from a brass jet on the carb cover. If so, the float is either set too high or saturated with fuel, or the float needle is malfunctioning. If the leak occurs when the motor is running, you need to adjust the float height, replace the float or replace the needle and seat and adjust the float height, depending on the problem. You should also check the spark plugs for fouling on the rich fuel mixture

 

[tompowers85]

Re: NO POWER out of mercury 8500 1975

I ment the brass jet in the front of the carb. I could not think of the name when i typed it before. I just replaced the floats but i did not replace the jets. I thought i gaped the floats correctly but i can check again. The old float were really bad.

 

[Chris1956]

Re: NO POWER out of mercury 8500 1975

Tom, You should not have to replace the Carb mixture jets(main jet, idle restriction jet). They don't usually wear out. Follow the service manual procedure to set the float height and idle mixture screw. If it still leaks fuel out of the top of the carb, replace the float needle and its seat.

 

[tomkatesam]

Re: NO POWER out of mercury 8500 1975

I found the problem on the engine. I baught another engine (the same kind) and had the same problem, it was my gas tank. For some reason that i do not know the tank had some venting problems. I replaced the tank with a new 19 gal and both motors run great. I use one for parts now.