2004 Merc 135hp blown power head after servicd

Bassstripe12

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Joined
Aug 1, 2022
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I have twin 135 mercs that were serviced about a week ago, part of that service was removing the starboard cylinder head and retapping a spark plug socket. (As well as thermostats, water pumps and new spark plugs).
The second time driving after service, starboard engine goes out at ~4000rpms, get back to dock where work was done, mechanic takes a quick look and says yep, blown starboard powerhead.

Working on getting a third party mechanic to take a look, but what are the possible causes of this and how likely is this just a coincidence? I understand it can be caused by overheating but the gaskets, water pumps and thermostats were all just replaced. I’m thinking they could have not replaced the powerhead correctly, or installed replacement parts wrong, leading to this issue. Any help is appreciated
 

jimmbo

Supreme Mariner
Joined
May 24, 2004
Messages
13,463
How many Hours did it run before it quit?
Which 135 is/was it? Carbed, FI, DFI?
 

Dave1027

Lieutenant Junior Grade
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May 25, 2010
Messages
1,080
"Blown powerhead" is such a vague term. It sounds like this so-called mechanic is a knucklehead but did he give any more detail as to what broke? Was the motor peeing? Did you happen to check motor temperature when running?
 

Bassstripe12

Recruit
Joined
Aug 1, 2022
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Mechanic said he could see a crack in it right away once the cover was off, temp started high and cooled off once we started moving/rpms were up, no alarms, water was moving/ pissing
 

Bassstripe12

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Aug 1, 2022
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Will do once I get back to the boat. They also failed to check the oil with the service, even though it was was a 300 hour service, and was requested before they started
 
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