engine repair - possible blown head gasket

[blakeyoung]

I have a 2013 Yamaha 4 HP outboard motor (model F4MLH). I was running it for the first time in about 1 year, just getting the motor warm. It was at full throttle for about 2 minutes when there was a pop or boom and the engine instantly lost power and died. There were a few drops of oil that leaked out near the cylinder, but I couldn't see exactly where they were coming from. Pulling on the starter cord now gives no resistance and it will not start at all.

Does it sound like the head gasket might have blown? The motor itself cost about $1500 new at the time, which is the same price today to buy a new one. Provided it is the head gasket and no other damage, would it be worth repairing? I guess it depends on the amount of damage. Just not sure what kind of bill I'd be looking at and if it would be worth it.

 

[rejesterd]

It's hard to say if it would be worth fixing or not, because it's not clear why the issue occurred. At full throttle, do you know where the rpms were at? It might not be able to handle full throttle given the load on it.

If it were me, I would at least remove the valve cover and see if one of the valves is stuck open. That would cause oil to leak out, and also cause it to back-fire (which would make a loud noise like you heard). If it is indeed just a blown head gasket, then a new one is about $20. How much a marine mechanic would charge you to diagnose and fix it, I'm not really sure. I would say it's at least worth buying the service manual and following the steps for inspecting the power unit.

 

[racerone]

Checked oil level ?------Possibly a broken connecting rod.----Or broken valve.------Should be easy to inspect.