Merc black max Siezed pistons?

[MercBlackMax1]

Hey everyone. Today i put my boat in the water Mercury black max150 and went out for a test run in the morning. Everything went ok exept i thought it was over heating a bit around 240 F. The spout where the water comes out seemed ok. So i dicided to go for another ride at 5 and i got out of the river on idle and floored it when i got to the lake and all of a sudden it felt like i hit somthing (but i didnt) and the motor made a wierd broken nooise and died . When i tried to start it up again i could hear the starter trying to turn the motor but nothing to it. when i got back to my dock i tried toiurng the fly wheel with my hands and was able to (difficultly) so i tried to start it again and it fired up but with a rattling sound any ideas of what might be going on ?

thanks Matt

 

[Jlawsen]

Re: Merc black max Siezed pistons?

Sorry to hear that Matt, I think you know now that 185 is max on the temp. My bet is that it's #2 that stuck. Flame over the piston edge caused carbon/aluminum build up on the ring lands and eventually a ring hangs in the exhaust port breaking the ring and sometimes the piston skirt. It's rare to bend or break a rod on a stock motor, they are not the weakest point unless it was a flawed casting to begin with.

Pull the heads and have a look at all the cylinders. If it is just #2 and it's not too bad you can usually fix it without pulling the powerhead. Obvously you still need to fix the cooling problem or the fuel problem whichever it turns out to be.

 

[aussieflash]

Re: Merc black max Siezed pistons?

My 88 V6 overheat sender is set to 240 deg.The outer cyl head sender is usually set at 190 deg.