488 merc

[lynnboy021]

does anyone know whats the compression psi for a 488 merc? my motor cranks over fine and has spark and fuel but does not wanna start driving me nuts... another ? can a alt that is making less then 12 volts make a motor not start?

 

[legoman67]

Re: 488 merc

no, the alt wont affect it firing assuming you have a good battery. If the alt isn't working the engine will slowly drain the battery and eventually will die when the battery is flat.

Compression shouldn't stop an engine from firing, it may not run great if you have poor compression, but it should still run.

How do you know its getting fuel?

 

[jerryjerry05]

Re: 488 merc

U sure there is spark/fuel at the plugs?The compression should be even on all cylinders.They don't give actual readings because of the difference in guages.Your guage might read 20 to 30# different than mine.Look for the same or close across all cylinders.
Try starting fluid?
Is the shift interupt switch activated?J

 

[Bondo]

Re: 488 merc

Ayuh,... 'bout 150psi, give ot take abit...

 

[Don S]

Re: 488 merc

Anything over 100 will allow it to start. You say it has spark, is it bright blue spark and jump 3/8" gap? If it's a weak yellow, it probably won't start.

 

[lynnboy021]

Re: 488 merc

i forget what color spark it is cuz i did not start the boat yet i just left it like it is from last year. i am thinking of just getting a 23 or 25 ft boat with a small kitchen and toilt room lol. you guys think i can pull a 23 or 25ft boat with double axel trailer with a 98 4x4 blazer? when i try to start up the boat i will tell u guys what happen oh how i know i am getting fule? i hook up a small tank with a clear fuel filter and i can see fule going through the filter and into the carb and i remove all plugs and crank over the motor and all firer i just forgot what color it was.... maybe its off timing???

 

[littlebookworm]

Re: 488 merc

Start by checking the basics: charged battery, electricity to starter, fuel to carb, good spark at plugs. If any of these is a "No", then backtrack. Check you coil voltage, points and condensor, distributor cap and wires, neutral safety switch,and timing. That should get you started. Don't forget to have water connected through muffs or you'll burn up the water pump impeller in seconds.