Two fire tenders were sent to the fish quay at 1.05pm where Genesis, which is registered in Peel, in the Isle of Man, was docked.
Smoke was seen to be coming from the exhaust and firefighters were soon tackling flames.
Skipper Tony Middlemas said he had visited the island for a rest break when he saw and smelt the smoke.
The vessel had travelled from Plymouth, which took 10 hours, and was taking some time out before going dredging for scallops.
Watch commander Gary Van der Linden said the tide was low, which helped them access the vessel by using the steps on the fish quay. The vessel was moored to the quay.
'We established overheating in lagging and woodwork surrounding the engine.'