Ohm is ok if...
You are looking for a dead short. If the problem is intermittant then an Ohm meter is of limited use. 1) How old is the coax? If 10+/- years old then I would replace w/ marine grade regardless.2) Try replacing the connectors at both ends of the coax. But you will have to cut the coax back until the outer braid is shiny/clean/uncorroded. If the outer braid is oxidized/dull/corroded well back of the end of the coax, it may be a sign it's time to replace it. Note, you may not have enough slack to cut the coax back.3) Then borrow or buy an SWR (Standing Wave Ratio) meter designed for 150mhz band and hook it up in-line between the radio, and the coax leading to the antenna. Transmit on the radio (with antenna attached to the other end of the coax!). If you get a high SWR - 3:1 or higher, then you have a problem with either the coax or the antenna, or both. Many things effect SWR including height above ground. Ideally the SWR should be at or near 1:1, but if your testing the antenna close to the ground you may not see a 1:1 SWR. Length of coax can also affect SWR - which is why it's important to keep the run of coax as short as practicle.Note, if you check the SWR, then transmit only long enough to get a reading. If there is a high SWR, you can quickly fry the transmitter in your radio. Some radios are self- protecting from a high swr - they autmatically refuse to xmit or shut down if high SWR is encountered - but don't assume your radio is one of those unless you know it for a fact. 4) The Antenna itself could fail, as most 150mhz marine antenna have a coil inside which if exposed to the elements will corrode. Also, the coil can be damaged by a near-miss lightening strike (a direct hit would most likely obliterate the antenna).Hope this helpsMike