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Joe, Marine Mechanic
Category: Boat
Satisfied Customers: 7251
Experience:  ASE, electronics, Marine mechanical and electronics, pwc, wiring, all around repair tech,
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I had my 8.1L 496 Mag winterized 10/10/14 by a boat n service

Customer Question

I had my 8.1L 496 Mag winterized 10/10/14 by a boat n service dealer... When I took it out for the first time in late May it got hot and shut the engine down within the first mile. A local marine mechanic started with the heat exchanger and it failed the compression test at the radiator shop. So we ordered a new one and then ran it to find out the raw water pump wasn't working, it was bad but the housing wasn't bad. After getting it fixed ran the boat and had miss to the engine (ENGINE HURT at this point, got to HOT)... The local marine mechanic doesn't tackle big blocks anymore so I took to our local auto mechanic guru. Didn't take him long to know engine was hurt, he found the 5&7 low on one and no compression to the other! Need OVERHAUL or find reman.
I guess what I'm wondering or asking is, could the winterizing process be the root of the problem??? I know their can be coincidences but this baby ran perfect at the end of last season and has been a one owner since 2006 with only 175 hours on it... Your thoughts
Signed, Expensive Mile
Submitted: 2 years ago.
Category: Boat
Expert:  Jason replied 2 years ago.
Hello my name is ***** ***** am I speaking with?Is it related to the winterizing, doesn't sound like it. How often did you have the impeller changed out?
Expert:  Joe replied 2 years ago.
Thank you for allowing me to assist you, my name is ***** ***** I will be happy to assist you with your concern today.
Actually it could be many things, one of the things that is common overlooked is checking/replacing the raw water pump impeller once a year be it just checking and or replacing, doesn't matter if it shows bad or not. When they fail they usually come apart and when this happens pieces of it go up stream/downstream and clog the system and what happens when someone changes the impeller is they usually don't think of where the pieces went, they just replace the impeller. I have worked on many where that was the case and due to them not removing they caused further problems such as engine overheating leading to head gaskets, exhaust gaskets and melting hoses, exhaust getting so hot it melts harnesses, etc.
When I service them I flush the entire system, pull the thermostat and check for debris on non closed system cooled engines, otherwise instead turn to the heat exchanger.
Have them remove the head and check if the problem is rings/cylinders or is just a bad head gasket, you may get lucky and find she only cooked the head gasket. In terms of your engine it has a closed system cooling system, thus raw water impeller would have been stuck in the heat exchanger and not in the thermostat.
In my personal opinion, if it did not have any sign of misfire to it before replacing the heat exchanger then it should not have been let get that hot after replacing it, I always watch the gauge and if it's getting to hot I shut it down before any problems can occur, then again I am also monitoring the engine via a ir temp gun.
Thank you!
- Joe
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