Question

I get two yanmar 3JH43 40 horse power on my catamaran. Two weeks ago the guy which is taking care of the boat had the bad idea to run the engine without open the intake cooling seawater. He was running the engine during around 20 minutes and ten he stopped it. The result is the two flexible impeller was destroyed. Yestarday I changed the impellers and the engine was running good, the only problem was on the starboard engine which was not posible to stop using just the stop button swicth. I had to push the stop button swicth and in the same time turn the key switch off. Some minutes later I turn on again the engine and I notice that from the cables conected to the solenoid above the starting motor some smoke was came out and it was smelling of burnt. In the same time there were a noise like a big fun turning so I again I switch of the engine with the same system I did before and I notice that the starter motor and the solenoid were very hot. What do you think could be the problem?