Looking at a used boat with twin 454, 330hp version. Broker furnished a recent compression test reading that ranges anywhere from 105 psi to 120 psi. Successive readings were all within 10% of the adjacent cylinder.

What range should a 1989 motor have?

Hour meter reads only 450 hours, but who knows if it's true.

Another way would be a leakdown test
this is where you can really see what condition it is in.

I just compression-checked my motor (330/454 w/mild cam) and all cylinders read 165 psi. Motor was rebuilt about 5 yrs. ago and has 265 hrs.

D. Ocean
Pompano Beach, FLA

My 330's in my old Baja had 155 lbs with 750 hrs on them.

Not an expert here, but those #'s seem really low. It could be that it hasn't run in a long time, which can influence the #'s. However, I think you should see somewhere approx. between 140-160 lbs.

You said this has twins? Both motors show this reading?

No more than 10% from lowest to highest.

Could be sticking rings from sitting, otherwise it needs some money spent on it.