Lehman 120 compression

FF · Mar 1, 2020

The budget way to monitor a boats DC electric is to wire a set of terminals to the dash area from the big contact an the starter , and the starter case..

Plug in that harbor Freight meter before staring, observe the volts, 12.8 or so, crank away on the starter , usually 9.5 volts in minimum while cranking.
When the beast starts look at the meter again the V should now be higher than before the start.

After an hour or so the V should be about 13.8 to 14.4 , all is well.DONE!

diver dave · Mar 1, 2020

Yes, you can do a lot with a little bit of instrumentation. Volts is easy and effective, if done at the correct point in the system, per FF.
One can also consider a Hall effect device on the battery wire. Run to a portable storage scope, you can read instantaneous starter current to move each cylinder. Any outliers become obvious as compression varies. Much faster than pulling injectors, etc. you can also see the effect of multi Vis oils, and temperature.

jleonard · Mar 1, 2020

When I did my starter voltage drop test, I had 9.8 V at the starter terminal while it was cranking.
It was not enough. It was cranking very slowly.
After the new cable I had 10.8 v. That was able to spin the starter like crazy.

Lehman 120 compression

FF

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diver dave

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jleonard

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