350 Mercruiser over heated - now what?

[Jeremy M. Schoettle]

Let me start by saying that I know very little about engines and I am sorry for my ignorance. But here it goes. I have a 2001 350 Mercruiser MAG MPI Inboard with 254 hours on it. A couple of weeks ago the engine alarm sounded and so I shut the engine down immediately. The funny thing is I was only just starting my boat cruise in idle for about five minutes. The engine appeared to be really hot for just being on idle for about 10 minutes. I took it in and they tell me the water pump needs replaced. They also said that water got into the cylinders (at least that is what I think they said)and that there might be other damage. <br /><br />What other damage are they suggesting and how much is that going to cost? Ultimately, is my engine ever going to be the same?

 

[doman]

Re: 350 Mercruiser over heated - now what?

i would change the water pump and forget about the water in the cylinders for now ...water doesnt get in to the cylinders because of bad water pump unless engine gets really overheated and head gasket goes...just change your pump and you should be good to go ..btw how do you know its the water pump and not the termostat or the impeller ...i would check on that first before spending money on the water pump ..they usually start leaking when the go bad <br /><br />Dom

 

[kopy kat]

Re: 350 Mercruiser over heated - now what?

Jeremy--been there, done that! My 5.7 EFI overheated at 95 hrs. due to a bad impeller-which SeaRay paid for---cracked both heads-and yes, that does let water into the cylinders. <br />At 135 hrs. it overheated again, due to poor installation of the new impeller by the mechanic-and yes water does get in the cylinders when the heads crack due to overheating ( I know-I'm repeating myself). Get to a good shop and have the heads pulled and magnafluxed to check for cacks--a total replacement with new heads will run $2000+. AS others have posted on this board-replace your impeller often-it's cheaper than new heads. Larry