I have spent over a year installing a rebuilt 235 in a 53 3100. The oil pump lost it's prime & it took several 30 second spins with the plugs out just to get oil to the port the gage connects to. Is it correct to expect to lose prime after several months ?

Also with no filter on the motor if I put the gage on the lower oil port & plug the one just above it ( that I assume would be the return port for a filter ) is that the correct way. I do not want mess up my oil flow or pressure.

Thanks, Kelly