Checking out motor failure.

[Mark42]

Had time to take head off the 40hp and see what was what. The top cylinder is scored bad enough to drop compression down to 30psi. The bottom cylinder has 140 psi compression, same as it was last month. So I assume it was not a VRO failure. Head gasket looks like it was not leaking anywhere. <br /><br />I drained out a cup or so of gas from the fuel line at the quick connect and it is clean with no sign of water. The fuel filter looks new and clean inside as viewed from the inlet end. <br /><br />The pistons were not burned or show burn marks. Nothing hanging out in the intake or exhaust ports that I could see.<br /><br />Motor has somewhere around 60 - 70 hours, definitally less than 100. <br /><br />Blackbird wants me to send them back the whole powerhead to determine what the failure is. I may take them up on on it. <br /><br />I want to identify the cause of the cylinder/piston failure, but don't want to disassemble the motor then have the shop say they can't determine cause of failure because I took it apart already.<br /><br />Any suggestions?

 

[BoatBuoy]

Re: Checking out motor failure.

Were you using Amsoil?

 

[CATransplant]

Re: Checking out motor failure.

I'd do that...send the powerhead back to Blackbird. Let them see if they can figure out what caused the failure. Was this a rebuilt powerhead?

 

[Mark42]

Re: Checking out motor failure.

Yeah, it is a rebuilt. It ran fine right up until the time it died. Pump was pumping water very well. Even removed the thermostat to be sure it was not an over heating problem when heading back to the marina.

 

[Dhadley]

Re: Checking out motor failure.

Describe what the piston looks like. Is the top edge burned at all? Look close right by the exhaust port, thats the hottest spot in there.<br /><br />What plugs were in it?<br /><br />Just curious -- what oil?<br /><br />As much as (I think) you use the boat we're assuming the fuel was less than 30-45 days old. And 87 octane, right?<br /><br />If all the piston damage is on the sides of the piston, look real close at the bottom carb.

 

[willamettejeff]

Re: Checking out motor failure.

Ok, I give Dhadley, why would one look at the bottom carb when the damage was to the top cylinder? Curious, just curious.

 

[Dhadley]

Re: Checking out motor failure.

Ah-ha!! Someone is paying attention!! Thats so he'll know what a good carb looks like.<br /><br />(Hows that for covering up???)

 

[Goodoleboy]

Re: Checking out motor failure.

Your slick Hadley...gota hand it to ya....Ha Ha!

 

[willamettejeff]

Re: Checking out motor failure.

Originally posted by Dhadley:<br /> Ah-ha!! Someone is paying attention!! Thats so he'll know what a good carb looks like.<br /><br />(Hows that for covering up???)

Works for me.